--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/contrib/grey.py Sun Oct 06 14:13:03 2019 -0700
@@ -0,0 +1,4094 @@
+# no-check-code because 3rd party
+import ast
+import asyncio
+from concurrent.futures import Executor, ProcessPoolExecutor
+from contextlib import contextmanager
+from datetime import datetime
+from enum import Enum
+from functools import lru_cache, partial, wraps
+import io
+import itertools
+import logging
+from multiprocessing import Manager, freeze_support
+import os
+from pathlib import Path
+import pickle
+import re
+import signal
+import sys
+import tempfile
+import tokenize
+import traceback
+from typing import (
+ Any,
+ Callable,
+ Collection,
+ Dict,
+ Generator,
+ Generic,
+ Iterable,
+ Iterator,
+ List,
+ Optional,
+ Pattern,
+ Sequence,
+ Set,
+ Tuple,
+ TypeVar,
+ Union,
+ cast,
+)
+
+from appdirs import user_cache_dir
+from attr import dataclass, evolve, Factory
+import click
+import toml
+from typed_ast import ast3, ast27
+
+# lib2to3 fork
+from blib2to3.pytree import Node, Leaf, type_repr
+from blib2to3 import pygram, pytree
+from blib2to3.pgen2 import driver, token
+from blib2to3.pgen2.grammar import Grammar
+from blib2to3.pgen2.parse import ParseError
+
+__version__ = '19.3b1.dev95+gdc1add6.d20191005'
+
+DEFAULT_LINE_LENGTH = 88
+DEFAULT_EXCLUDES = (
+ r"/(\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|_build|buck-out|build|dist)/"
+)
+DEFAULT_INCLUDES = r"\.pyi?$"
+CACHE_DIR = Path(user_cache_dir("black", version=__version__))
+
+
+# types
+FileContent = str
+Encoding = str
+NewLine = str
+Depth = int
+NodeType = int
+LeafID = int
+Priority = int
+Index = int
+LN = Union[Leaf, Node]
+SplitFunc = Callable[["Line", Collection["Feature"]], Iterator["Line"]]
+Timestamp = float
+FileSize = int
+CacheInfo = Tuple[Timestamp, FileSize]
+Cache = Dict[Path, CacheInfo]
+out = partial(click.secho, bold=True, err=True)
+err = partial(click.secho, fg="red", err=True)
+
+pygram.initialize(CACHE_DIR)
+syms = pygram.python_symbols
+
+
+class NothingChanged(UserWarning):
+ """Raised when reformatted code is the same as source."""
+
+
+class CannotSplit(Exception):
+ """A readable split that fits the allotted line length is impossible."""
+
+
+class InvalidInput(ValueError):
+ """Raised when input source code fails all parse attempts."""
+
+
+class WriteBack(Enum):
+ NO = 0
+ YES = 1
+ DIFF = 2
+ CHECK = 3
+
+ @classmethod
+ def from_configuration(cls, *, check: bool, diff: bool) -> "WriteBack":
+ if check and not diff:
+ return cls.CHECK
+
+ return cls.DIFF if diff else cls.YES
+
+
+class Changed(Enum):
+ NO = 0
+ CACHED = 1
+ YES = 2
+
+
+class TargetVersion(Enum):
+ PY27 = 2
+ PY33 = 3
+ PY34 = 4
+ PY35 = 5
+ PY36 = 6
+ PY37 = 7
+ PY38 = 8
+
+ def is_python2(self) -> bool:
+ return self is TargetVersion.PY27
+
+
+PY36_VERSIONS = {TargetVersion.PY36, TargetVersion.PY37, TargetVersion.PY38}
+
+
+class Feature(Enum):
+ # All string literals are unicode
+ UNICODE_LITERALS = 1
+ F_STRINGS = 2
+ NUMERIC_UNDERSCORES = 3
+ TRAILING_COMMA_IN_CALL = 4
+ TRAILING_COMMA_IN_DEF = 5
+ # The following two feature-flags are mutually exclusive, and exactly one should be
+ # set for every version of python.
+ ASYNC_IDENTIFIERS = 6
+ ASYNC_KEYWORDS = 7
+ ASSIGNMENT_EXPRESSIONS = 8
+ POS_ONLY_ARGUMENTS = 9
+
+
+VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
+ TargetVersion.PY27: {Feature.ASYNC_IDENTIFIERS},
+ TargetVersion.PY33: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
+ TargetVersion.PY34: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
+ TargetVersion.PY35: {
+ Feature.UNICODE_LITERALS,
+ Feature.TRAILING_COMMA_IN_CALL,
+ Feature.ASYNC_IDENTIFIERS,
+ },
+ TargetVersion.PY36: {
+ Feature.UNICODE_LITERALS,
+ Feature.F_STRINGS,
+ Feature.NUMERIC_UNDERSCORES,
+ Feature.TRAILING_COMMA_IN_CALL,
+ Feature.TRAILING_COMMA_IN_DEF,
+ Feature.ASYNC_IDENTIFIERS,
+ },
+ TargetVersion.PY37: {
+ Feature.UNICODE_LITERALS,
+ Feature.F_STRINGS,
+ Feature.NUMERIC_UNDERSCORES,
+ Feature.TRAILING_COMMA_IN_CALL,
+ Feature.TRAILING_COMMA_IN_DEF,
+ Feature.ASYNC_KEYWORDS,
+ },
+ TargetVersion.PY38: {
+ Feature.UNICODE_LITERALS,
+ Feature.F_STRINGS,
+ Feature.NUMERIC_UNDERSCORES,
+ Feature.TRAILING_COMMA_IN_CALL,
+ Feature.TRAILING_COMMA_IN_DEF,
+ Feature.ASYNC_KEYWORDS,
+ Feature.ASSIGNMENT_EXPRESSIONS,
+ Feature.POS_ONLY_ARGUMENTS,
+ },
+}
+
+
+@dataclass
+class FileMode:
+ target_versions: Set[TargetVersion] = Factory(set)
+ line_length: int = DEFAULT_LINE_LENGTH
+ string_normalization: bool = True
+ is_pyi: bool = False
+
+ def get_cache_key(self) -> str:
+ if self.target_versions:
+ version_str = ",".join(
+ str(version.value)
+ for version in sorted(self.target_versions, key=lambda v: v.value)
+ )
+ else:
+ version_str = "-"
+ parts = [
+ version_str,
+ str(self.line_length),
+ str(int(self.string_normalization)),
+ str(int(self.is_pyi)),
+ ]
+ return ".".join(parts)
+
+
+def supports_feature(target_versions: Set[TargetVersion], feature: Feature) -> bool:
+ return all(feature in VERSION_TO_FEATURES[version] for version in target_versions)
+
+
+def read_pyproject_toml(
+ ctx: click.Context, param: click.Parameter, value: Union[str, int, bool, None]
+) -> Optional[str]:
+ """Inject Black configuration from "pyproject.toml" into defaults in `ctx`.
+
+ Returns the path to a successfully found and read configuration file, None
+ otherwise.
+ """
+ assert not isinstance(value, (int, bool)), "Invalid parameter type passed"
+ if not value:
+ root = find_project_root(ctx.params.get("src", ()))
+ path = root / "pyproject.toml"
+ if path.is_file():
+ value = str(path)
+ else:
+ return None
+
+ try:
+ pyproject_toml = toml.load(value)
+ config = pyproject_toml.get("tool", {}).get("black", {})
+ except (toml.TomlDecodeError, OSError) as e:
+ raise click.FileError(
+ filename=value, hint=f"Error reading configuration file: {e}"
+ )
+
+ if not config:
+ return None
+
+ if ctx.default_map is None:
+ ctx.default_map = {}
+ ctx.default_map.update( # type: ignore # bad types in .pyi
+ {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}
+ )
+ return value
+
+
+@click.command(context_settings=dict(help_option_names=["-h", "--help"]))
+@click.option("-c", "--code", type=str, help="Format the code passed in as a string.")
+@click.option(
+ "-l",
+ "--line-length",
+ type=int,
+ default=DEFAULT_LINE_LENGTH,
+ help="How many characters per line to allow.",
+ show_default=True,
+)
+@click.option(
+ "-t",
+ "--target-version",
+ type=click.Choice([v.name.lower() for v in TargetVersion]),
+ callback=lambda c, p, v: [TargetVersion[val.upper()] for val in v],
+ multiple=True,
+ help=(
+ "Python versions that should be supported by Black's output. [default: "
+ "per-file auto-detection]"
+ ),
+)
+@click.option(
+ "--py36",
+ is_flag=True,
+ help=(
+ "Allow using Python 3.6-only syntax on all input files. This will put "
+ "trailing commas in function signatures and calls also after *args and "
+ "**kwargs. Deprecated; use --target-version instead. "
+ "[default: per-file auto-detection]"
+ ),
+)
+@click.option(
+ "--pyi",
+ is_flag=True,
+ help=(
+ "Format all input files like typing stubs regardless of file extension "
+ "(useful when piping source on standard input)."
+ ),
+)
+@click.option(
+ "-S",
+ "--skip-string-normalization",
+ is_flag=True,
+ help="Don't normalize string quotes or prefixes.",
+)
+@click.option(
+ "--check",
+ is_flag=True,
+ help=(
+ "Don't write the files back, just return the status. Return code 0 "
+ "means nothing would change. Return code 1 means some files would be "
+ "reformatted. Return code 123 means there was an internal error."
+ ),
+)
+@click.option(
+ "--diff",
+ is_flag=True,
+ help="Don't write the files back, just output a diff for each file on stdout.",
+)
+@click.option(
+ "--fast/--safe",
+ is_flag=True,
+ help="If --fast given, skip temporary sanity checks. [default: --safe]",
+)
+@click.option(
+ "--include",
+ type=str,
+ default=DEFAULT_INCLUDES,
+ help=(
+ "A regular expression that matches files and directories that should be "
+ "included on recursive searches. An empty value means all files are "
+ "included regardless of the name. Use forward slashes for directories on "
+ "all platforms (Windows, too). Exclusions are calculated first, inclusions "
+ "later."
+ ),
+ show_default=True,
+)
+@click.option(
+ "--exclude",
+ type=str,
+ default=DEFAULT_EXCLUDES,
+ help=(
+ "A regular expression that matches files and directories that should be "
+ "excluded on recursive searches. An empty value means no paths are excluded. "
+ "Use forward slashes for directories on all platforms (Windows, too). "
+ "Exclusions are calculated first, inclusions later."
+ ),
+ show_default=True,
+)
+@click.option(
+ "-q",
+ "--quiet",
+ is_flag=True,
+ help=(
+ "Don't emit non-error messages to stderr. Errors are still emitted; "
+ "silence those with 2>/dev/null."
+ ),
+)
+@click.option(
+ "-v",
+ "--verbose",
+ is_flag=True,
+ help=(
+ "Also emit messages to stderr about files that were not changed or were "
+ "ignored due to --exclude=."
+ ),
+)
+@click.version_option(version=__version__)
+@click.argument(
+ "src",
+ nargs=-1,
+ type=click.Path(
+ exists=True, file_okay=True, dir_okay=True, readable=True, allow_dash=True
+ ),
+ is_eager=True,
+)
+@click.option(
+ "--config",
+ type=click.Path(
+ exists=False, file_okay=True, dir_okay=False, readable=True, allow_dash=False
+ ),
+ is_eager=True,
+ callback=read_pyproject_toml,
+ help="Read configuration from PATH.",
+)
+@click.pass_context
+def main(
+ ctx: click.Context,
+ code: Optional[str],
+ line_length: int,
+ target_version: List[TargetVersion],
+ check: bool,
+ diff: bool,
+ fast: bool,
+ pyi: bool,
+ py36: bool,
+ skip_string_normalization: bool,
+ quiet: bool,
+ verbose: bool,
+ include: str,
+ exclude: str,
+ src: Tuple[str],
+ config: Optional[str],
+) -> None:
+ """The uncompromising code formatter."""
+ write_back = WriteBack.from_configuration(check=check, diff=diff)
+ if target_version:
+ if py36:
+ err(f"Cannot use both --target-version and --py36")
+ ctx.exit(2)
+ else:
+ versions = set(target_version)
+ elif py36:
+ err(
+ "--py36 is deprecated and will be removed in a future version. "
+ "Use --target-version py36 instead."
+ )
+ versions = PY36_VERSIONS
+ else:
+ # We'll autodetect later.
+ versions = set()
+ mode = FileMode(
+ target_versions=versions,
+ line_length=line_length,
+ is_pyi=pyi,
+ string_normalization=not skip_string_normalization,
+ )
+ if config and verbose:
+ out(f"Using configuration from {config}.", bold=False, fg="blue")
+ if code is not None:
+ print(format_str(code, mode=mode))
+ ctx.exit(0)
+ try:
+ include_regex = re_compile_maybe_verbose(include)
+ except re.error:
+ err(f"Invalid regular expression for include given: {include!r}")
+ ctx.exit(2)
+ try:
+ exclude_regex = re_compile_maybe_verbose(exclude)
+ except re.error:
+ err(f"Invalid regular expression for exclude given: {exclude!r}")
+ ctx.exit(2)
+ report = Report(check=check, quiet=quiet, verbose=verbose)
+ root = find_project_root(src)
+ sources: Set[Path] = set()
+ path_empty(src, quiet, verbose, ctx)
+ for s in src:
+ p = Path(s)
+ if p.is_dir():
+ sources.update(
+ gen_python_files_in_dir(p, root, include_regex, exclude_regex, report)
+ )
+ elif p.is_file() or s == "-":
+ # if a file was explicitly given, we don't care about its extension
+ sources.add(p)
+ else:
+ err(f"invalid path: {s}")
+ if len(sources) == 0:
+ if verbose or not quiet:
+ out("No Python files are present to be formatted. Nothing to do 😴")
+ ctx.exit(0)
+
+ if len(sources) == 1:
+ reformat_one(
+ src=sources.pop(),
+ fast=fast,
+ write_back=write_back,
+ mode=mode,
+ report=report,
+ )
+ else:
+ reformat_many(
+ sources=sources, fast=fast, write_back=write_back, mode=mode, report=report
+ )
+
+ if verbose or not quiet:
+ out("Oh no! 💥 💔 💥" if report.return_code else "All done! ✨ 🍰 ✨")
+ click.secho(str(report), err=True)
+ ctx.exit(report.return_code)
+
+
+def path_empty(src: Tuple[str], quiet: bool, verbose: bool, ctx: click.Context) -> None:
+ """
+ Exit if there is no `src` provided for formatting
+ """
+ if not src:
+ if verbose or not quiet:
+ out("No Path provided. Nothing to do 😴")
+ ctx.exit(0)
+
+
+def reformat_one(
+ src: Path, fast: bool, write_back: WriteBack, mode: FileMode, report: "Report"
+) -> None:
+ """Reformat a single file under `src` without spawning child processes.
+
+ `fast`, `write_back`, and `mode` options are passed to
+ :func:`format_file_in_place` or :func:`format_stdin_to_stdout`.
+ """
+ try:
+ changed = Changed.NO
+ if not src.is_file() and str(src) == "-":
+ if format_stdin_to_stdout(fast=fast, write_back=write_back, mode=mode):
+ changed = Changed.YES
+ else:
+ cache: Cache = {}
+ if write_back != WriteBack.DIFF:
+ cache = read_cache(mode)
+ res_src = src.resolve()
+ if res_src in cache and cache[res_src] == get_cache_info(res_src):
+ changed = Changed.CACHED
+ if changed is not Changed.CACHED and format_file_in_place(
+ src, fast=fast, write_back=write_back, mode=mode
+ ):
+ changed = Changed.YES
+ if (write_back is WriteBack.YES and changed is not Changed.CACHED) or (
+ write_back is WriteBack.CHECK and changed is Changed.NO
+ ):
+ write_cache(cache, [src], mode)
+ report.done(src, changed)
+ except Exception as exc:
+ report.failed(src, str(exc))
+
+
+def reformat_many(
+ sources: Set[Path],
+ fast: bool,
+ write_back: WriteBack,
+ mode: FileMode,
+ report: "Report",
+) -> None:
+ """Reformat multiple files using a ProcessPoolExecutor."""
+ loop = asyncio.get_event_loop()
+ worker_count = os.cpu_count()
+ if sys.platform == "win32":
+ # Work around https://bugs.python.org/issue26903
+ worker_count = min(worker_count, 61)
+ executor = ProcessPoolExecutor(max_workers=worker_count)
+ try:
+ loop.run_until_complete(
+ schedule_formatting(
+ sources=sources,
+ fast=fast,
+ write_back=write_back,
+ mode=mode,
+ report=report,
+ loop=loop,
+ executor=executor,
+ )
+ )
+ finally:
+ shutdown(loop)
+ executor.shutdown()
+
+
+async def schedule_formatting(
+ sources: Set[Path],
+ fast: bool,
+ write_back: WriteBack,
+ mode: FileMode,
+ report: "Report",
+ loop: asyncio.AbstractEventLoop,
+ executor: Executor,
+) -> None:
+ """Run formatting of `sources` in parallel using the provided `executor`.
+
+ (Use ProcessPoolExecutors for actual parallelism.)
+
+ `write_back`, `fast`, and `mode` options are passed to
+ :func:`format_file_in_place`.
+ """
+ cache: Cache = {}
+ if write_back != WriteBack.DIFF:
+ cache = read_cache(mode)
+ sources, cached = filter_cached(cache, sources)
+ for src in sorted(cached):
+ report.done(src, Changed.CACHED)
+ if not sources:
+ return
+
+ cancelled = []
+ sources_to_cache = []
+ lock = None
+ if write_back == WriteBack.DIFF:
+ # For diff output, we need locks to ensure we don't interleave output
+ # from different processes.
+ manager = Manager()
+ lock = manager.Lock()
+ tasks = {
+ asyncio.ensure_future(
+ loop.run_in_executor(
+ executor, format_file_in_place, src, fast, mode, write_back, lock
+ )
+ ): src
+ for src in sorted(sources)
+ }
+ pending: Iterable[asyncio.Future] = tasks.keys()
+ try:
+ loop.add_signal_handler(signal.SIGINT, cancel, pending)
+ loop.add_signal_handler(signal.SIGTERM, cancel, pending)
+ except NotImplementedError:
+ # There are no good alternatives for these on Windows.
+ pass
+ while pending:
+ done, _ = await asyncio.wait(pending, return_when=asyncio.FIRST_COMPLETED)
+ for task in done:
+ src = tasks.pop(task)
+ if task.cancelled():
+ cancelled.append(task)
+ elif task.exception():
+ report.failed(src, str(task.exception()))
+ else:
+ changed = Changed.YES if task.result() else Changed.NO
+ # If the file was written back or was successfully checked as
+ # well-formatted, store this information in the cache.
+ if write_back is WriteBack.YES or (
+ write_back is WriteBack.CHECK and changed is Changed.NO
+ ):
+ sources_to_cache.append(src)
+ report.done(src, changed)
+ if cancelled:
+ await asyncio.gather(*cancelled, loop=loop, return_exceptions=True)
+ if sources_to_cache:
+ write_cache(cache, sources_to_cache, mode)
+
+
+def format_file_in_place(
+ src: Path,
+ fast: bool,
+ mode: FileMode,
+ write_back: WriteBack = WriteBack.NO,
+ lock: Any = None, # multiprocessing.Manager().Lock() is some crazy proxy
+) -> bool:
+ """Format file under `src` path. Return True if changed.
+
+ If `write_back` is DIFF, write a diff to stdout. If it is YES, write reformatted
+ code to the file.
+ `mode` and `fast` options are passed to :func:`format_file_contents`.
+ """
+ if src.suffix == ".pyi":
+ mode = evolve(mode, is_pyi=True)
+
+ then = datetime.utcfromtimestamp(src.stat().st_mtime)
+ with open(src, "rb") as buf:
+ src_contents, encoding, newline = decode_bytes(buf.read())
+ try:
+ dst_contents = format_file_contents(src_contents, fast=fast, mode=mode)
+ except NothingChanged:
+ return False
+
+ if write_back == write_back.YES:
+ with open(src, "w", encoding=encoding, newline=newline) as f:
+ f.write(dst_contents)
+ elif write_back == write_back.DIFF:
+ now = datetime.utcnow()
+ src_name = f"{src}\t{then} +0000"
+ dst_name = f"{src}\t{now} +0000"
+ diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
+
+ with lock or nullcontext():
+ f = io.TextIOWrapper(
+ sys.stdout.buffer,
+ encoding=encoding,
+ newline=newline,
+ write_through=True,
+ )
+ f.write(diff_contents)
+ f.detach()
+
+ return True
+
+
+def format_stdin_to_stdout(
+ fast: bool, *, write_back: WriteBack = WriteBack.NO, mode: FileMode
+) -> bool:
+ """Format file on stdin. Return True if changed.
+
+ If `write_back` is YES, write reformatted code back to stdout. If it is DIFF,
+ write a diff to stdout. The `mode` argument is passed to
+ :func:`format_file_contents`.
+ """
+ then = datetime.utcnow()
+ src, encoding, newline = decode_bytes(sys.stdin.buffer.read())
+ dst = src
+ try:
+ dst = format_file_contents(src, fast=fast, mode=mode)
+ return True
+
+ except NothingChanged:
+ return False
+
+ finally:
+ f = io.TextIOWrapper(
+ sys.stdout.buffer, encoding=encoding, newline=newline, write_through=True
+ )
+ if write_back == WriteBack.YES:
+ f.write(dst)
+ elif write_back == WriteBack.DIFF:
+ now = datetime.utcnow()
+ src_name = f"STDIN\t{then} +0000"
+ dst_name = f"STDOUT\t{now} +0000"
+ f.write(diff(src, dst, src_name, dst_name))
+ f.detach()
+
+
+def format_file_contents(
+ src_contents: str, *, fast: bool, mode: FileMode
+) -> FileContent:
+ """Reformat contents a file and return new contents.
+
+ If `fast` is False, additionally confirm that the reformatted code is
+ valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it.
+ `mode` is passed to :func:`format_str`.
+ """
+ if src_contents.strip() == "":
+ raise NothingChanged
+
+ dst_contents = format_str(src_contents, mode=mode)
+ if src_contents == dst_contents:
+ raise NothingChanged
+
+ if not fast:
+ assert_equivalent(src_contents, dst_contents)
+ assert_stable(src_contents, dst_contents, mode=mode)
+ return dst_contents
+
+
+def format_str(src_contents: str, *, mode: FileMode) -> FileContent:
+ """Reformat a string and return new contents.
+
+ `mode` determines formatting options, such as how many characters per line are
+ allowed.
+ """
+ src_node = lib2to3_parse(src_contents.lstrip(), mode.target_versions)
+ dst_contents = []
+ future_imports = get_future_imports(src_node)
+ if mode.target_versions:
+ versions = mode.target_versions
+ else:
+ versions = detect_target_versions(src_node)
+ normalize_fmt_off(src_node)
+ lines = LineGenerator(
+ remove_u_prefix="unicode_literals" in future_imports
+ or supports_feature(versions, Feature.UNICODE_LITERALS),
+ is_pyi=mode.is_pyi,
+ normalize_strings=mode.string_normalization,
+ )
+ elt = EmptyLineTracker(is_pyi=mode.is_pyi)
+ empty_line = Line()
+ after = 0
+ split_line_features = {
+ feature
+ for feature in {Feature.TRAILING_COMMA_IN_CALL, Feature.TRAILING_COMMA_IN_DEF}
+ if supports_feature(versions, feature)
+ }
+ for current_line in lines.visit(src_node):
+ for _ in range(after):
+ dst_contents.append(str(empty_line))
+ before, after = elt.maybe_empty_lines(current_line)
+ for _ in range(before):
+ dst_contents.append(str(empty_line))
+ for line in split_line(
+ current_line, line_length=mode.line_length, features=split_line_features
+ ):
+ dst_contents.append(str(line))
+ return "".join(dst_contents)
+
+
+def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
+ """Return a tuple of (decoded_contents, encoding, newline).
+
+ `newline` is either CRLF or LF but `decoded_contents` is decoded with
+ universal newlines (i.e. only contains LF).
+ """
+ srcbuf = io.BytesIO(src)
+ encoding, lines = tokenize.detect_encoding(srcbuf.readline)
+ if not lines:
+ return "", encoding, "\n"
+
+ newline = "\r\n" if b"\r\n" == lines[0][-2:] else "\n"
+ srcbuf.seek(0)
+ with io.TextIOWrapper(srcbuf, encoding) as tiow:
+ return tiow.read(), encoding, newline
+
+
+def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
+ if not target_versions:
+ # No target_version specified, so try all grammars.
+ return [
+ # Python 3.7+
+ pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,
+ # Python 3.0-3.6
+ pygram.python_grammar_no_print_statement_no_exec_statement,
+ # Python 2.7 with future print_function import
+ pygram.python_grammar_no_print_statement,
+ # Python 2.7
+ pygram.python_grammar,
+ ]
+ elif all(version.is_python2() for version in target_versions):
+ # Python 2-only code, so try Python 2 grammars.
+ return [
+ # Python 2.7 with future print_function import
+ pygram.python_grammar_no_print_statement,
+ # Python 2.7
+ pygram.python_grammar,
+ ]
+ else:
+ # Python 3-compatible code, so only try Python 3 grammar.
+ grammars = []
+ # If we have to parse both, try to parse async as a keyword first
+ if not supports_feature(target_versions, Feature.ASYNC_IDENTIFIERS):
+ # Python 3.7+
+ grammars.append(
+ pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords # noqa: B950
+ )
+ if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):
+ # Python 3.0-3.6
+ grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)
+ # At least one of the above branches must have been taken, because every Python
+ # version has exactly one of the two 'ASYNC_*' flags
+ return grammars
+
+
+def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -> Node:
+ """Given a string with source, return the lib2to3 Node."""
+ if src_txt[-1:] != "\n":
+ src_txt += "\n"
+
+ for grammar in get_grammars(set(target_versions)):
+ drv = driver.Driver(grammar, pytree.convert)
+ try:
+ result = drv.parse_string(src_txt, True)
+ break
+
+ except ParseError as pe:
+ lineno, column = pe.context[1]
+ lines = src_txt.splitlines()
+ try:
+ faulty_line = lines[lineno - 1]
+ except IndexError:
+ faulty_line = "<line number missing in source>"
+ exc = InvalidInput(f"Cannot parse: {lineno}:{column}: {faulty_line}")
+ else:
+ raise exc from None
+
+ if isinstance(result, Leaf):
+ result = Node(syms.file_input, [result])
+ return result
+
+
+def lib2to3_unparse(node: Node) -> str:
+ """Given a lib2to3 node, return its string representation."""
+ code = str(node)
+ return code
+
+
+T = TypeVar("T")
+
+
+class Visitor(Generic[T]):
+ """Basic lib2to3 visitor that yields things of type `T` on `visit()`."""
+
+ def visit(self, node: LN) -> Iterator[T]:
+ """Main method to visit `node` and its children.
+
+ It tries to find a `visit_*()` method for the given `node.type`, like
+ `visit_simple_stmt` for Node objects or `visit_INDENT` for Leaf objects.
+ If no dedicated `visit_*()` method is found, chooses `visit_default()`
+ instead.
+
+ Then yields objects of type `T` from the selected visitor.
+ """
+ if node.type < 256:
+ name = token.tok_name[node.type]
+ else:
+ name = type_repr(node.type)
+ yield from getattr(self, f"visit_{name}", self.visit_default)(node)
+
+ def visit_default(self, node: LN) -> Iterator[T]:
+ """Default `visit_*()` implementation. Recurses to children of `node`."""
+ if isinstance(node, Node):
+ for child in node.children:
+ yield from self.visit(child)
+
+
+@dataclass
+class DebugVisitor(Visitor[T]):
+ tree_depth: int = 0
+
+ def visit_default(self, node: LN) -> Iterator[T]:
+ indent = " " * (2 * self.tree_depth)
+ if isinstance(node, Node):
+ _type = type_repr(node.type)
+ out(f"{indent}{_type}", fg="yellow")
+ self.tree_depth += 1
+ for child in node.children:
+ yield from self.visit(child)
+
+ self.tree_depth -= 1
+ out(f"{indent}/{_type}", fg="yellow", bold=False)
+ else:
+ _type = token.tok_name.get(node.type, str(node.type))
+ out(f"{indent}{_type}", fg="blue", nl=False)
+ if node.prefix:
+ # We don't have to handle prefixes for `Node` objects since
+ # that delegates to the first child anyway.
+ out(f" {node.prefix!r}", fg="green", bold=False, nl=False)
+ out(f" {node.value!r}", fg="blue", bold=False)
+
+ @classmethod
+ def show(cls, code: Union[str, Leaf, Node]) -> None:
+ """Pretty-print the lib2to3 AST of a given string of `code`.
+
+ Convenience method for debugging.
+ """
+ v: DebugVisitor[None] = DebugVisitor()
+ if isinstance(code, str):
+ code = lib2to3_parse(code)
+ list(v.visit(code))
+
+
+WHITESPACE = {token.DEDENT, token.INDENT, token.NEWLINE}
+STATEMENT = {
+ syms.if_stmt,
+ syms.while_stmt,
+ syms.for_stmt,
+ syms.try_stmt,
+ syms.except_clause,
+ syms.with_stmt,
+ syms.funcdef,
+ syms.classdef,
+}
+STANDALONE_COMMENT = 153
+token.tok_name[STANDALONE_COMMENT] = "STANDALONE_COMMENT"
+LOGIC_OPERATORS = {"and", "or"}
+COMPARATORS = {
+ token.LESS,
+ token.GREATER,
+ token.EQEQUAL,
+ token.NOTEQUAL,
+ token.LESSEQUAL,
+ token.GREATEREQUAL,
+}
+MATH_OPERATORS = {
+ token.VBAR,
+ token.CIRCUMFLEX,
+ token.AMPER,
+ token.LEFTSHIFT,
+ token.RIGHTSHIFT,
+ token.PLUS,
+ token.MINUS,
+ token.STAR,
+ token.SLASH,
+ token.DOUBLESLASH,
+ token.PERCENT,
+ token.AT,
+ token.TILDE,
+ token.DOUBLESTAR,
+}
+STARS = {token.STAR, token.DOUBLESTAR}
+VARARGS_SPECIALS = STARS | {token.SLASH}
+VARARGS_PARENTS = {
+ syms.arglist,
+ syms.argument, # double star in arglist
+ syms.trailer, # single argument to call
+ syms.typedargslist,
+ syms.varargslist, # lambdas
+}
+UNPACKING_PARENTS = {
+ syms.atom, # single element of a list or set literal
+ syms.dictsetmaker,
+ syms.listmaker,
+ syms.testlist_gexp,
+ syms.testlist_star_expr,
+}
+TEST_DESCENDANTS = {
+ syms.test,
+ syms.lambdef,
+ syms.or_test,
+ syms.and_test,
+ syms.not_test,
+ syms.comparison,
+ syms.star_expr,
+ syms.expr,
+ syms.xor_expr,
+ syms.and_expr,
+ syms.shift_expr,
+ syms.arith_expr,
+ syms.trailer,
+ syms.term,
+ syms.power,
+}
+ASSIGNMENTS = {
+ "=",
+ "+=",
+ "-=",
+ "*=",
+ "@=",
+ "/=",
+ "%=",
+ "&=",
+ "|=",
+ "^=",
+ "<<=",
+ ">>=",
+ "**=",
+ "//=",
+}
+COMPREHENSION_PRIORITY = 20
+COMMA_PRIORITY = 18
+TERNARY_PRIORITY = 16
+LOGIC_PRIORITY = 14
+STRING_PRIORITY = 12
+COMPARATOR_PRIORITY = 10
+MATH_PRIORITIES = {
+ token.VBAR: 9,
+ token.CIRCUMFLEX: 8,
+ token.AMPER: 7,
+ token.LEFTSHIFT: 6,
+ token.RIGHTSHIFT: 6,
+ token.PLUS: 5,
+ token.MINUS: 5,
+ token.STAR: 4,
+ token.SLASH: 4,
+ token.DOUBLESLASH: 4,
+ token.PERCENT: 4,
+ token.AT: 4,
+ token.TILDE: 3,
+ token.DOUBLESTAR: 2,
+}
+DOT_PRIORITY = 1
+
+
+@dataclass
+class BracketTracker:
+ """Keeps track of brackets on a line."""
+
+ depth: int = 0
+ bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = Factory(dict)
+ delimiters: Dict[LeafID, Priority] = Factory(dict)
+ previous: Optional[Leaf] = None
+ _for_loop_depths: List[int] = Factory(list)
+ _lambda_argument_depths: List[int] = Factory(list)
+
+ def mark(self, leaf: Leaf) -> None:
+ """Mark `leaf` with bracket-related metadata. Keep track of delimiters.
+
+ All leaves receive an int `bracket_depth` field that stores how deep
+ within brackets a given leaf is. 0 means there are no enclosing brackets
+ that started on this line.
+
+ If a leaf is itself a closing bracket, it receives an `opening_bracket`
+ field that it forms a pair with. This is a one-directional link to
+ avoid reference cycles.
+
+ If a leaf is a delimiter (a token on which Black can split the line if
+ needed) and it's on depth 0, its `id()` is stored in the tracker's
+ `delimiters` field.
+ """
+ if leaf.type == token.COMMENT:
+ return
+
+ self.maybe_decrement_after_for_loop_variable(leaf)
+ self.maybe_decrement_after_lambda_arguments(leaf)
+ if leaf.type in CLOSING_BRACKETS:
+ self.depth -= 1
+ opening_bracket = self.bracket_match.pop((self.depth, leaf.type))
+ leaf.opening_bracket = opening_bracket
+ leaf.bracket_depth = self.depth
+ if self.depth == 0:
+ delim = is_split_before_delimiter(leaf, self.previous)
+ if delim and self.previous is not None:
+ self.delimiters[id(self.previous)] = delim
+ else:
+ delim = is_split_after_delimiter(leaf, self.previous)
+ if delim:
+ self.delimiters[id(leaf)] = delim
+ if leaf.type in OPENING_BRACKETS:
+ self.bracket_match[self.depth, BRACKET[leaf.type]] = leaf
+ self.depth += 1
+ self.previous = leaf
+ self.maybe_increment_lambda_arguments(leaf)
+ self.maybe_increment_for_loop_variable(leaf)
+
+ def any_open_brackets(self) -> bool:
+ """Return True if there is an yet unmatched open bracket on the line."""
+ return bool(self.bracket_match)
+
+ def max_delimiter_priority(self, exclude: Iterable[LeafID] = ()) -> Priority:
+ """Return the highest priority of a delimiter found on the line.
+
+ Values are consistent with what `is_split_*_delimiter()` return.
+ Raises ValueError on no delimiters.
+ """
+ return max(v for k, v in self.delimiters.items() if k not in exclude)
+
+ def delimiter_count_with_priority(self, priority: Priority = 0) -> int:
+ """Return the number of delimiters with the given `priority`.
+
+ If no `priority` is passed, defaults to max priority on the line.
+ """
+ if not self.delimiters:
+ return 0
+
+ priority = priority or self.max_delimiter_priority()
+ return sum(1 for p in self.delimiters.values() if p == priority)
+
+ def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool:
+ """In a for loop, or comprehension, the variables are often unpacks.
+
+ To avoid splitting on the comma in this situation, increase the depth of
+ tokens between `for` and `in`.
+ """
+ if leaf.type == token.NAME and leaf.value == "for":
+ self.depth += 1
+ self._for_loop_depths.append(self.depth)
+ return True
+
+ return False
+
+ def maybe_decrement_after_for_loop_variable(self, leaf: Leaf) -> bool:
+ """See `maybe_increment_for_loop_variable` above for explanation."""
+ if (
+ self._for_loop_depths
+ and self._for_loop_depths[-1] == self.depth
+ and leaf.type == token.NAME
+ and leaf.value == "in"
+ ):
+ self.depth -= 1
+ self._for_loop_depths.pop()
+ return True
+
+ return False
+
+ def maybe_increment_lambda_arguments(self, leaf: Leaf) -> bool:
+ """In a lambda expression, there might be more than one argument.
+
+ To avoid splitting on the comma in this situation, increase the depth of
+ tokens between `lambda` and `:`.
+ """
+ if leaf.type == token.NAME and leaf.value == "lambda":
+ self.depth += 1
+ self._lambda_argument_depths.append(self.depth)
+ return True
+
+ return False
+
+ def maybe_decrement_after_lambda_arguments(self, leaf: Leaf) -> bool:
+ """See `maybe_increment_lambda_arguments` above for explanation."""
+ if (
+ self._lambda_argument_depths
+ and self._lambda_argument_depths[-1] == self.depth
+ and leaf.type == token.COLON
+ ):
+ self.depth -= 1
+ self._lambda_argument_depths.pop()
+ return True
+
+ return False
+
+ def get_open_lsqb(self) -> Optional[Leaf]:
+ """Return the most recent opening square bracket (if any)."""
+ return self.bracket_match.get((self.depth - 1, token.RSQB))
+
+
+@dataclass
+class Line:
+ """Holds leaves and comments. Can be printed with `str(line)`."""
+
+ depth: int = 0
+ leaves: List[Leaf] = Factory(list)
+ comments: Dict[LeafID, List[Leaf]] = Factory(dict) # keys ordered like `leaves`
+ bracket_tracker: BracketTracker = Factory(BracketTracker)
+ inside_brackets: bool = False
+ should_explode: bool = False
+
+ def append(self, leaf: Leaf, preformatted: bool = False) -> None:
+ """Add a new `leaf` to the end of the line.
+
+ Unless `preformatted` is True, the `leaf` will receive a new consistent
+ whitespace prefix and metadata applied by :class:`BracketTracker`.
+ Trailing commas are maybe removed, unpacked for loop variables are
+ demoted from being delimiters.
+
+ Inline comments are put aside.
+ """
+ has_value = leaf.type in BRACKETS or bool(leaf.value.strip())
+ if not has_value:
+ return
+
+ if token.COLON == leaf.type and self.is_class_paren_empty:
+ del self.leaves[-2:]
+ if self.leaves and not preformatted:
+ # Note: at this point leaf.prefix should be empty except for
+ # imports, for which we only preserve newlines.
+ leaf.prefix += whitespace(
+ leaf, complex_subscript=self.is_complex_subscript(leaf)
+ )
+ if self.inside_brackets or not preformatted:
+ self.bracket_tracker.mark(leaf)
+ self.maybe_remove_trailing_comma(leaf)
+ if not self.append_comment(leaf):
+ self.leaves.append(leaf)
+
+ def append_safe(self, leaf: Leaf, preformatted: bool = False) -> None:
+ """Like :func:`append()` but disallow invalid standalone comment structure.
+
+ Raises ValueError when any `leaf` is appended after a standalone comment
+ or when a standalone comment is not the first leaf on the line.
+ """
+ if self.bracket_tracker.depth == 0:
+ if self.is_comment:
+ raise ValueError("cannot append to standalone comments")
+
+ if self.leaves and leaf.type == STANDALONE_COMMENT:
+ raise ValueError(
+ "cannot append standalone comments to a populated line"
+ )
+
+ self.append(leaf, preformatted=preformatted)
+
+ @property
+ def is_comment(self) -> bool:
+ """Is this line a standalone comment?"""
+ return len(self.leaves) == 1 and self.leaves[0].type == STANDALONE_COMMENT
+
+ @property
+ def is_decorator(self) -> bool:
+ """Is this line a decorator?"""
+ return bool(self) and self.leaves[0].type == token.AT
+
+ @property
+ def is_import(self) -> bool:
+ """Is this an import line?"""
+ return bool(self) and is_import(self.leaves[0])
+
+ @property
+ def is_class(self) -> bool:
+ """Is this line a class definition?"""
+ return (
+ bool(self)
+ and self.leaves[0].type == token.NAME
+ and self.leaves[0].value == "class"
+ )
+
+ @property
+ def is_stub_class(self) -> bool:
+ """Is this line a class definition with a body consisting only of "..."?"""
+ return self.is_class and self.leaves[-3:] == [
+ Leaf(token.DOT, ".") for _ in range(3)
+ ]
+
+ @property
+ def is_collection_with_optional_trailing_comma(self) -> bool:
+ """Is this line a collection literal with a trailing comma that's optional?
+
+ Note that the trailing comma in a 1-tuple is not optional.
+ """
+ if not self.leaves or len(self.leaves) < 4:
+ return False
+ # Look for and address a trailing colon.
+ if self.leaves[-1].type == token.COLON:
+ closer = self.leaves[-2]
+ close_index = -2
+ else:
+ closer = self.leaves[-1]
+ close_index = -1
+ if closer.type not in CLOSING_BRACKETS or self.inside_brackets:
+ return False
+ if closer.type == token.RPAR:
+ # Tuples require an extra check, because if there's only
+ # one element in the tuple removing the comma unmakes the
+ # tuple.
+ #
+ # We also check for parens before looking for the trailing
+ # comma because in some cases (eg assigning a dict
+ # literal) the literal gets wrapped in temporary parens
+ # during parsing. This case is covered by the
+ # collections.py test data.
+ opener = closer.opening_bracket
+ for _open_index, leaf in enumerate(self.leaves):
+ if leaf is opener:
+ break
+ else:
+ # Couldn't find the matching opening paren, play it safe.
+ return False
+ commas = 0
+ comma_depth = self.leaves[close_index - 1].bracket_depth
+ for leaf in self.leaves[_open_index + 1 : close_index]:
+ if leaf.bracket_depth == comma_depth and leaf.type == token.COMMA:
+ commas += 1
+ if commas > 1:
+ # We haven't looked yet for the trailing comma because
+ # we might also have caught noop parens.
+ return self.leaves[close_index - 1].type == token.COMMA
+ elif commas == 1:
+ return False # it's either a one-tuple or didn't have a trailing comma
+ if self.leaves[close_index - 1].type in CLOSING_BRACKETS:
+ close_index -= 1
+ closer = self.leaves[close_index]
+ if closer.type == token.RPAR:
+ # TODO: this is a gut feeling. Will we ever see this?
+ return False
+ if self.leaves[close_index - 1].type != token.COMMA:
+ return False
+ return True
+
+ @property
+ def is_def(self) -> bool:
+ """Is this a function definition? (Also returns True for async defs.)"""
+ try:
+ first_leaf = self.leaves[0]
+ except IndexError:
+ return False
+
+ try:
+ second_leaf: Optional[Leaf] = self.leaves[1]
+ except IndexError:
+ second_leaf = None
+ return (first_leaf.type == token.NAME and first_leaf.value == "def") or (
+ first_leaf.type == token.ASYNC
+ and second_leaf is not None
+ and second_leaf.type == token.NAME
+ and second_leaf.value == "def"
+ )
+
+ @property
+ def is_class_paren_empty(self) -> bool:
+ """Is this a class with no base classes but using parentheses?
+
+ Those are unnecessary and should be removed.
+ """
+ return (
+ bool(self)
+ and len(self.leaves) == 4
+ and self.is_class
+ and self.leaves[2].type == token.LPAR
+ and self.leaves[2].value == "("
+ and self.leaves[3].type == token.RPAR
+ and self.leaves[3].value == ")"
+ )
+
+ @property
+ def is_triple_quoted_string(self) -> bool:
+ """Is the line a triple quoted string?"""
+ return (
+ bool(self)
+ and self.leaves[0].type == token.STRING
+ and self.leaves[0].value.startswith(('"""', "'''"))
+ )
+
+ def contains_standalone_comments(self, depth_limit: int = sys.maxsize) -> bool:
+ """If so, needs to be split before emitting."""
+ for leaf in self.leaves:
+ if leaf.type == STANDALONE_COMMENT:
+ if leaf.bracket_depth <= depth_limit:
+ return True
+ return False
+
+ def contains_uncollapsable_type_comments(self) -> bool:
+ ignored_ids = set()
+ try:
+ last_leaf = self.leaves[-1]
+ ignored_ids.add(id(last_leaf))
+ if last_leaf.type == token.COMMA or (
+ last_leaf.type == token.RPAR and not last_leaf.value
+ ):
+ # When trailing commas or optional parens are inserted by Black for
+ # consistency, comments after the previous last element are not moved
+ # (they don't have to, rendering will still be correct). So we ignore
+ # trailing commas and invisible.
+ last_leaf = self.leaves[-2]
+ ignored_ids.add(id(last_leaf))
+ except IndexError:
+ return False
+
+ # A type comment is uncollapsable if it is attached to a leaf
+ # that isn't at the end of the line (since that could cause it
+ # to get associated to a different argument) or if there are
+ # comments before it (since that could cause it to get hidden
+ # behind a comment.
+ comment_seen = False
+ for leaf_id, comments in self.comments.items():
+ for comment in comments:
+ if is_type_comment(comment):
+ if leaf_id not in ignored_ids or comment_seen:
+ return True
+
+ comment_seen = True
+
+ return False
+
+ def contains_unsplittable_type_ignore(self) -> bool:
+ if not self.leaves:
+ return False
+
+ # If a 'type: ignore' is attached to the end of a line, we
+ # can't split the line, because we can't know which of the
+ # subexpressions the ignore was meant to apply to.
+ #
+ # We only want this to apply to actual physical lines from the
+ # original source, though: we don't want the presence of a
+ # 'type: ignore' at the end of a multiline expression to
+ # justify pushing it all onto one line. Thus we
+ # (unfortunately) need to check the actual source lines and
+ # only report an unsplittable 'type: ignore' if this line was
+ # one line in the original code.
+ if self.leaves[0].lineno == self.leaves[-1].lineno:
+ for comment in self.comments.get(id(self.leaves[-1]), []):
+ if is_type_comment(comment, " ignore"):
+ return True
+
+ return False
+
+ def contains_multiline_strings(self) -> bool:
+ for leaf in self.leaves:
+ if is_multiline_string(leaf):
+ return True
+
+ return False
+
+ def maybe_remove_trailing_comma(self, closing: Leaf) -> bool:
+ """Remove trailing comma if there is one and it's safe."""
+ if not (self.leaves and self.leaves[-1].type == token.COMMA):
+ return False
+ # We remove trailing commas only in the case of importing a
+ # single name from a module.
+ if not (
+ self.leaves
+ and self.is_import
+ and len(self.leaves) > 4
+ and self.leaves[-1].type == token.COMMA
+ and closing.type in CLOSING_BRACKETS
+ and self.leaves[-4].type == token.NAME
+ and (
+ # regular `from foo import bar,`
+ self.leaves[-4].value == "import"
+ # `from foo import (bar as baz,)
+ or (
+ len(self.leaves) > 6
+ and self.leaves[-6].value == "import"
+ and self.leaves[-3].value == "as"
+ )
+ # `from foo import bar as baz,`
+ or (
+ len(self.leaves) > 5
+ and self.leaves[-5].value == "import"
+ and self.leaves[-3].value == "as"
+ )
+ )
+ and closing.type == token.RPAR
+ ):
+ return False
+
+ self.remove_trailing_comma()
+ return True
+
+ def append_comment(self, comment: Leaf) -> bool:
+ """Add an inline or standalone comment to the line."""
+ if (
+ comment.type == STANDALONE_COMMENT
+ and self.bracket_tracker.any_open_brackets()
+ ):
+ comment.prefix = ""
+ return False
+
+ if comment.type != token.COMMENT:
+ return False
+
+ if not self.leaves:
+ comment.type = STANDALONE_COMMENT
+ comment.prefix = ""
+ return False
+
+ last_leaf = self.leaves[-1]
+ if (
+ last_leaf.type == token.RPAR
+ and not last_leaf.value
+ and last_leaf.parent
+ and len(list(last_leaf.parent.leaves())) <= 3
+ and not is_type_comment(comment)
+ ):
+ # Comments on an optional parens wrapping a single leaf should belong to
+ # the wrapped node except if it's a type comment. Pinning the comment like
+ # this avoids unstable formatting caused by comment migration.
+ if len(self.leaves) < 2:
+ comment.type = STANDALONE_COMMENT
+ comment.prefix = ""
+ return False
+ last_leaf = self.leaves[-2]
+ self.comments.setdefault(id(last_leaf), []).append(comment)
+ return True
+
+ def comments_after(self, leaf: Leaf) -> List[Leaf]:
+ """Generate comments that should appear directly after `leaf`."""
+ return self.comments.get(id(leaf), [])
+
+ def remove_trailing_comma(self) -> None:
+ """Remove the trailing comma and moves the comments attached to it."""
+ trailing_comma = self.leaves.pop()
+ trailing_comma_comments = self.comments.pop(id(trailing_comma), [])
+ self.comments.setdefault(id(self.leaves[-1]), []).extend(
+ trailing_comma_comments
+ )
+
+ def is_complex_subscript(self, leaf: Leaf) -> bool:
+ """Return True iff `leaf` is part of a slice with non-trivial exprs."""
+ open_lsqb = self.bracket_tracker.get_open_lsqb()
+ if open_lsqb is None:
+ return False
+
+ subscript_start = open_lsqb.next_sibling
+
+ if isinstance(subscript_start, Node):
+ if subscript_start.type == syms.listmaker:
+ return False
+
+ if subscript_start.type == syms.subscriptlist:
+ subscript_start = child_towards(subscript_start, leaf)
+ return subscript_start is not None and any(
+ n.type in TEST_DESCENDANTS for n in subscript_start.pre_order()
+ )
+
+ def __str__(self) -> str:
+ """Render the line."""
+ if not self:
+ return "\n"
+
+ indent = " " * self.depth
+ leaves = iter(self.leaves)
+ first = next(leaves)
+ res = f"{first.prefix}{indent}{first.value}"
+ for leaf in leaves:
+ res += str(leaf)
+ for comment in itertools.chain.from_iterable(self.comments.values()):
+ res += str(comment)
+ return res + "\n"
+
+ def __bool__(self) -> bool:
+ """Return True if the line has leaves or comments."""
+ return bool(self.leaves or self.comments)
+
+
+@dataclass
+class EmptyLineTracker:
+ """Provides a stateful method that returns the number of potential extra
+ empty lines needed before and after the currently processed line.
+
+ Note: this tracker works on lines that haven't been split yet. It assumes
+ the prefix of the first leaf consists of optional newlines. Those newlines
+ are consumed by `maybe_empty_lines()` and included in the computation.
+ """
+
+ is_pyi: bool = False
+ previous_line: Optional[Line] = None
+ previous_after: int = 0
+ previous_defs: List[int] = Factory(list)
+
+ def maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
+ """Return the number of extra empty lines before and after the `current_line`.
+
+ This is for separating `def`, `async def` and `class` with extra empty
+ lines (two on module-level).
+ """
+ before, after = self._maybe_empty_lines(current_line)
+ before = (
+ # Black should not insert empty lines at the beginning
+ # of the file
+ 0
+ if self.previous_line is None
+ else before - self.previous_after
+ )
+ self.previous_after = after
+ self.previous_line = current_line
+ return before, after
+
+ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
+ max_allowed = 1
+ if current_line.depth == 0:
+ max_allowed = 1 if self.is_pyi else 2
+ if current_line.leaves:
+ # Consume the first leaf's extra newlines.
+ first_leaf = current_line.leaves[0]
+ before = first_leaf.prefix.count("\n")
+ before = min(before, max_allowed)
+ first_leaf.prefix = ""
+ else:
+ before = 0
+ depth = current_line.depth
+ while self.previous_defs and self.previous_defs[-1] >= depth:
+ self.previous_defs.pop()
+ if self.is_pyi:
+ before = 0 if depth else 1
+ else:
+ before = 1 if depth else 2
+ if current_line.is_decorator or current_line.is_def or current_line.is_class:
+ return self._maybe_empty_lines_for_class_or_def(current_line, before)
+
+ if (
+ self.previous_line
+ and self.previous_line.is_import
+ and not current_line.is_import
+ and depth == self.previous_line.depth
+ ):
+ return (before or 1), 0
+
+ if (
+ self.previous_line
+ and self.previous_line.is_class
+ and current_line.is_triple_quoted_string
+ ):
+ return before, 1
+
+ return before, 0
+
+ def _maybe_empty_lines_for_class_or_def(
+ self, current_line: Line, before: int
+ ) -> Tuple[int, int]:
+ if not current_line.is_decorator:
+ self.previous_defs.append(current_line.depth)
+ if self.previous_line is None:
+ # Don't insert empty lines before the first line in the file.
+ return 0, 0
+
+ if self.previous_line.is_decorator:
+ return 0, 0
+
+ if self.previous_line.depth < current_line.depth and (
+ self.previous_line.is_class or self.previous_line.is_def
+ ):
+ return 0, 0
+
+ if (
+ self.previous_line.is_comment
+ and self.previous_line.depth == current_line.depth
+ and before == 0
+ ):
+ return 0, 0
+
+ if self.is_pyi:
+ if self.previous_line.depth > current_line.depth:
+ newlines = 1
+ elif current_line.is_class or self.previous_line.is_class:
+ if current_line.is_stub_class and self.previous_line.is_stub_class:
+ # No blank line between classes with an empty body
+ newlines = 0
+ else:
+ newlines = 1
+ elif current_line.is_def and not self.previous_line.is_def:
+ # Blank line between a block of functions and a block of non-functions
+ newlines = 1
+ else:
+ newlines = 0
+ else:
+ newlines = 2
+ if current_line.depth and newlines:
+ newlines -= 1
+ return newlines, 0
+
+
+@dataclass
+class LineGenerator(Visitor[Line]):
+ """Generates reformatted Line objects. Empty lines are not emitted.
+
+ Note: destroys the tree it's visiting by mutating prefixes of its leaves
+ in ways that will no longer stringify to valid Python code on the tree.
+ """
+
+ is_pyi: bool = False
+ normalize_strings: bool = True
+ current_line: Line = Factory(Line)
+ remove_u_prefix: bool = False
+
+ def line(self, indent: int = 0) -> Iterator[Line]:
+ """Generate a line.
+
+ If the line is empty, only emit if it makes sense.
+ If the line is too long, split it first and then generate.
+
+ If any lines were generated, set up a new current_line.
+ """
+ if not self.current_line:
+ self.current_line.depth += indent
+ return # Line is empty, don't emit. Creating a new one unnecessary.
+
+ complete_line = self.current_line
+ self.current_line = Line(depth=complete_line.depth + indent)
+ yield complete_line
+
+ def visit_default(self, node: LN) -> Iterator[Line]:
+ """Default `visit_*()` implementation. Recurses to children of `node`."""
+ if isinstance(node, Leaf):
+ any_open_brackets = self.current_line.bracket_tracker.any_open_brackets()
+ for comment in generate_comments(node):
+ if any_open_brackets:
+ # any comment within brackets is subject to splitting
+ self.current_line.append(comment)
+ elif comment.type == token.COMMENT:
+ # regular trailing comment
+ self.current_line.append(comment)
+ yield from self.line()
+
+ else:
+ # regular standalone comment
+ yield from self.line()
+
+ self.current_line.append(comment)
+ yield from self.line()
+
+ normalize_prefix(node, inside_brackets=any_open_brackets)
+ if self.normalize_strings and node.type == token.STRING:
+ normalize_string_prefix(node, remove_u_prefix=self.remove_u_prefix)
+ normalize_string_quotes(node)
+ if node.type == token.NUMBER:
+ normalize_numeric_literal(node)
+ if node.type not in WHITESPACE:
+ self.current_line.append(node)
+ yield from super().visit_default(node)
+
+ def visit_atom(self, node: Node) -> Iterator[Line]:
+ # Always make parentheses invisible around a single node, because it should
+ # not be needed (except in the case of yield, where removing the parentheses
+ # produces a SyntaxError).
+ if (
+ len(node.children) == 3
+ and isinstance(node.children[0], Leaf)
+ and node.children[0].type == token.LPAR
+ and isinstance(node.children[2], Leaf)
+ and node.children[2].type == token.RPAR
+ and isinstance(node.children[1], Leaf)
+ and not (
+ node.children[1].type == token.NAME
+ and node.children[1].value == "yield"
+ )
+ ):
+ node.children[0].value = ""
+ node.children[2].value = ""
+ yield from super().visit_default(node)
+
+ def visit_factor(self, node: Node) -> Iterator[Line]:
+ """Force parentheses between a unary op and a binary power:
+
+ -2 ** 8 -> -(2 ** 8)
+ """
+ child = node.children[1]
+ if child.type == syms.power and len(child.children) == 3:
+ lpar = Leaf(token.LPAR, "(")
+ rpar = Leaf(token.RPAR, ")")
+ index = child.remove() or 0
+ node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
+ yield from self.visit_default(node)
+
+ def visit_INDENT(self, node: Node) -> Iterator[Line]:
+ """Increase indentation level, maybe yield a line."""
+ # In blib2to3 INDENT never holds comments.
+ yield from self.line(+1)
+ yield from self.visit_default(node)
+
+ def visit_DEDENT(self, node: Node) -> Iterator[Line]:
+ """Decrease indentation level, maybe yield a line."""
+ # The current line might still wait for trailing comments. At DEDENT time
+ # there won't be any (they would be prefixes on the preceding NEWLINE).
+ # Emit the line then.
+ yield from self.line()
+
+ # While DEDENT has no value, its prefix may contain standalone comments
+ # that belong to the current indentation level. Get 'em.
+ yield from self.visit_default(node)
+
+ # Finally, emit the dedent.
+ yield from self.line(-1)
+
+ def visit_stmt(
+ self, node: Node, keywords: Set[str], parens: Set[str]
+ ) -> Iterator[Line]:
+ """Visit a statement.
+
+ This implementation is shared for `if`, `while`, `for`, `try`, `except`,
+ `def`, `with`, `class`, `assert` and assignments.
+
+ The relevant Python language `keywords` for a given statement will be
+ NAME leaves within it. This methods puts those on a separate line.
+
+ `parens` holds a set of string leaf values immediately after which
+ invisible parens should be put.
+ """
+ normalize_invisible_parens(node, parens_after=parens)
+ for child in node.children:
+ if child.type == token.NAME and child.value in keywords: # type: ignore
+ yield from self.line()
+
+ yield from self.visit(child)
+
+ def visit_suite(self, node: Node) -> Iterator[Line]:
+ """Visit a suite."""
+ if self.is_pyi and is_stub_suite(node):
+ yield from self.visit(node.children[2])
+ else:
+ yield from self.visit_default(node)
+
+ def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
+ """Visit a statement without nested statements."""
+ is_suite_like = node.parent and node.parent.type in STATEMENT
+ if is_suite_like:
+ if self.is_pyi and is_stub_body(node):
+ yield from self.visit_default(node)
+ else:
+ yield from self.line(+1)
+ yield from self.visit_default(node)
+ yield from self.line(-1)
+
+ else:
+ if not self.is_pyi or not node.parent or not is_stub_suite(node.parent):
+ yield from self.line()
+ yield from self.visit_default(node)
+
+ def visit_async_stmt(self, node: Node) -> Iterator[Line]:
+ """Visit `async def`, `async for`, `async with`."""
+ yield from self.line()
+
+ children = iter(node.children)
+ for child in children:
+ yield from self.visit(child)
+
+ if child.type == token.ASYNC:
+ break
+
+ internal_stmt = next(children)
+ for child in internal_stmt.children:
+ yield from self.visit(child)
+
+ def visit_decorators(self, node: Node) -> Iterator[Line]:
+ """Visit decorators."""
+ for child in node.children:
+ yield from self.line()
+ yield from self.visit(child)
+
+ def visit_SEMI(self, leaf: Leaf) -> Iterator[Line]:
+ """Remove a semicolon and put the other statement on a separate line."""
+ yield from self.line()
+
+ def visit_ENDMARKER(self, leaf: Leaf) -> Iterator[Line]:
+ """End of file. Process outstanding comments and end with a newline."""
+ yield from self.visit_default(leaf)
+ yield from self.line()
+
+ def visit_STANDALONE_COMMENT(self, leaf: Leaf) -> Iterator[Line]:
+ if not self.current_line.bracket_tracker.any_open_brackets():
+ yield from self.line()
+ yield from self.visit_default(leaf)
+
+ def __attrs_post_init__(self) -> None:
+ """You are in a twisty little maze of passages."""
+ v = self.visit_stmt
+ Ø: Set[str] = set()
+ self.visit_assert_stmt = partial(v, keywords={"assert"}, parens={"assert", ","})
+ self.visit_if_stmt = partial(
+ v, keywords={"if", "else", "elif"}, parens={"if", "elif"}
+ )
+ self.visit_while_stmt = partial(v, keywords={"while", "else"}, parens={"while"})
+ self.visit_for_stmt = partial(v, keywords={"for", "else"}, parens={"for", "in"})
+ self.visit_try_stmt = partial(
+ v, keywords={"try", "except", "else", "finally"}, parens=Ø
+ )
+ self.visit_except_clause = partial(v, keywords={"except"}, parens=Ø)
+ self.visit_with_stmt = partial(v, keywords={"with"}, parens=Ø)
+ self.visit_funcdef = partial(v, keywords={"def"}, parens=Ø)
+ self.visit_classdef = partial(v, keywords={"class"}, parens=Ø)
+ self.visit_expr_stmt = partial(v, keywords=Ø, parens=ASSIGNMENTS)
+ self.visit_return_stmt = partial(v, keywords={"return"}, parens={"return"})
+ self.visit_import_from = partial(v, keywords=Ø, parens={"import"})
+ self.visit_del_stmt = partial(v, keywords=Ø, parens={"del"})
+ self.visit_async_funcdef = self.visit_async_stmt
+ self.visit_decorated = self.visit_decorators
+
+
+IMPLICIT_TUPLE = {syms.testlist, syms.testlist_star_expr, syms.exprlist}
+BRACKET = {token.LPAR: token.RPAR, token.LSQB: token.RSQB, token.LBRACE: token.RBRACE}
+OPENING_BRACKETS = set(BRACKET.keys())
+CLOSING_BRACKETS = set(BRACKET.values())
+BRACKETS = OPENING_BRACKETS | CLOSING_BRACKETS
+ALWAYS_NO_SPACE = CLOSING_BRACKETS | {token.COMMA, STANDALONE_COMMENT}
+
+
+def whitespace(leaf: Leaf, *, complex_subscript: bool) -> str: # noqa: C901
+ """Return whitespace prefix if needed for the given `leaf`.
+
+ `complex_subscript` signals whether the given leaf is part of a subscription
+ which has non-trivial arguments, like arithmetic expressions or function calls.
+ """
+ NO = ""
+ SPACE = " "
+ DOUBLESPACE = " "
+ t = leaf.type
+ p = leaf.parent
+ v = leaf.value
+ if t in ALWAYS_NO_SPACE:
+ return NO
+
+ if t == token.COMMENT:
+ return DOUBLESPACE
+
+ assert p is not None, f"INTERNAL ERROR: hand-made leaf without parent: {leaf!r}"
+ if t == token.COLON and p.type not in {
+ syms.subscript,
+ syms.subscriptlist,
+ syms.sliceop,
+ }:
+ return NO
+
+ prev = leaf.prev_sibling
+ if not prev:
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type in OPENING_BRACKETS:
+ return NO
+
+ if t == token.COLON:
+ if prevp.type == token.COLON:
+ return NO
+
+ elif prevp.type != token.COMMA and not complex_subscript:
+ return NO
+
+ return SPACE
+
+ if prevp.type == token.EQUAL:
+ if prevp.parent:
+ if prevp.parent.type in {
+ syms.arglist,
+ syms.argument,
+ syms.parameters,
+ syms.varargslist,
+ }:
+ return NO
+
+ elif prevp.parent.type == syms.typedargslist:
+ # A bit hacky: if the equal sign has whitespace, it means we
+ # previously found it's a typed argument. So, we're using
+ # that, too.
+ return prevp.prefix
+
+ elif prevp.type in VARARGS_SPECIALS:
+ if is_vararg(prevp, within=VARARGS_PARENTS | UNPACKING_PARENTS):
+ return NO
+
+ elif prevp.type == token.COLON:
+ if prevp.parent and prevp.parent.type in {syms.subscript, syms.sliceop}:
+ return SPACE if complex_subscript else NO
+
+ elif (
+ prevp.parent
+ and prevp.parent.type == syms.factor
+ and prevp.type in MATH_OPERATORS
+ ):
+ return NO
+
+ elif (
+ prevp.type == token.RIGHTSHIFT
+ and prevp.parent
+ and prevp.parent.type == syms.shift_expr
+ and prevp.prev_sibling
+ and prevp.prev_sibling.type == token.NAME
+ and prevp.prev_sibling.value == "print" # type: ignore
+ ):
+ # Python 2 print chevron
+ return NO
+
+ elif prev.type in OPENING_BRACKETS:
+ return NO
+
+ if p.type in {syms.parameters, syms.arglist}:
+ # untyped function signatures or calls
+ if not prev or prev.type != token.COMMA:
+ return NO
+
+ elif p.type == syms.varargslist:
+ # lambdas
+ if prev and prev.type != token.COMMA:
+ return NO
+
+ elif p.type == syms.typedargslist:
+ # typed function signatures
+ if not prev:
+ return NO
+
+ if t == token.EQUAL:
+ if prev.type != syms.tname:
+ return NO
+
+ elif prev.type == token.EQUAL:
+ # A bit hacky: if the equal sign has whitespace, it means we
+ # previously found it's a typed argument. So, we're using that, too.
+ return prev.prefix
+
+ elif prev.type != token.COMMA:
+ return NO
+
+ elif p.type == syms.tname:
+ # type names
+ if not prev:
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type != token.COMMA:
+ return NO
+
+ elif p.type == syms.trailer:
+ # attributes and calls
+ if t == token.LPAR or t == token.RPAR:
+ return NO
+
+ if not prev:
+ if t == token.DOT:
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type != token.NUMBER:
+ return NO
+
+ elif t == token.LSQB:
+ return NO
+
+ elif prev.type != token.COMMA:
+ return NO
+
+ elif p.type == syms.argument:
+ # single argument
+ if t == token.EQUAL:
+ return NO
+
+ if not prev:
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type == token.LPAR:
+ return NO
+
+ elif prev.type in {token.EQUAL} | VARARGS_SPECIALS:
+ return NO
+
+ elif p.type == syms.decorator:
+ # decorators
+ return NO
+
+ elif p.type == syms.dotted_name:
+ if prev:
+ return NO
+
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type == token.AT or prevp.type == token.DOT:
+ return NO
+
+ elif p.type == syms.classdef:
+ if t == token.LPAR:
+ return NO
+
+ if prev and prev.type == token.LPAR:
+ return NO
+
+ elif p.type in {syms.subscript, syms.sliceop}:
+ # indexing
+ if not prev:
+ assert p.parent is not None, "subscripts are always parented"
+ if p.parent.type == syms.subscriptlist:
+ return SPACE
+
+ return NO
+
+ elif not complex_subscript:
+ return NO
+
+ elif p.type == syms.atom:
+ if prev and t == token.DOT:
+ # dots, but not the first one.
+ return NO
+
+ elif p.type == syms.dictsetmaker:
+ # dict unpacking
+ if prev and prev.type == token.DOUBLESTAR:
+ return NO
+
+ elif p.type in {syms.factor, syms.star_expr}:
+ # unary ops
+ if not prev:
+ prevp = preceding_leaf(p)
+ if not prevp or prevp.type in OPENING_BRACKETS:
+ return NO
+
+ prevp_parent = prevp.parent
+ assert prevp_parent is not None
+ if prevp.type == token.COLON and prevp_parent.type in {
+ syms.subscript,
+ syms.sliceop,
+ }:
+ return NO
+
+ elif prevp.type == token.EQUAL and prevp_parent.type == syms.argument:
+ return NO
+
+ elif t in {token.NAME, token.NUMBER, token.STRING}:
+ return NO
+
+ elif p.type == syms.import_from:
+ if t == token.DOT:
+ if prev and prev.type == token.DOT:
+ return NO
+
+ elif t == token.NAME:
+ if v == "import":
+ return SPACE
+
+ if prev and prev.type == token.DOT:
+ return NO
+
+ elif p.type == syms.sliceop:
+ return NO
+
+ return SPACE
+
+
+def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]:
+ """Return the first leaf that precedes `node`, if any."""
+ while node:
+ res = node.prev_sibling
+ if res:
+ if isinstance(res, Leaf):
+ return res
+
+ try:
+ return list(res.leaves())[-1]
+
+ except IndexError:
+ return None
+
+ node = node.parent
+ return None
+
+
+def child_towards(ancestor: Node, descendant: LN) -> Optional[LN]:
+ """Return the child of `ancestor` that contains `descendant`."""
+ node: Optional[LN] = descendant
+ while node and node.parent != ancestor:
+ node = node.parent
+ return node
+
+
+def container_of(leaf: Leaf) -> LN:
+ """Return `leaf` or one of its ancestors that is the topmost container of it.
+
+ By "container" we mean a node where `leaf` is the very first child.
+ """
+ same_prefix = leaf.prefix
+ container: LN = leaf
+ while container:
+ parent = container.parent
+ if parent is None:
+ break
+
+ if parent.children[0].prefix != same_prefix:
+ break
+
+ if parent.type == syms.file_input:
+ break
+
+ if parent.prev_sibling is not None and parent.prev_sibling.type in BRACKETS:
+ break
+
+ container = parent
+ return container
+
+
+def is_split_after_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
+ """Return the priority of the `leaf` delimiter, given a line break after it.
+
+ The delimiter priorities returned here are from those delimiters that would
+ cause a line break after themselves.
+
+ Higher numbers are higher priority.
+ """
+ if leaf.type == token.COMMA:
+ return COMMA_PRIORITY
+
+ return 0
+
+
+def is_split_before_delimiter(leaf: Leaf, previous: Optional[Leaf] = None) -> Priority:
+ """Return the priority of the `leaf` delimiter, given a line break before it.
+
+ The delimiter priorities returned here are from those delimiters that would
+ cause a line break before themselves.
+
+ Higher numbers are higher priority.
+ """
+ if is_vararg(leaf, within=VARARGS_PARENTS | UNPACKING_PARENTS):
+ # * and ** might also be MATH_OPERATORS but in this case they are not.
+ # Don't treat them as a delimiter.
+ return 0
+
+ if (
+ leaf.type == token.DOT
+ and leaf.parent
+ and leaf.parent.type not in {syms.import_from, syms.dotted_name}
+ and (previous is None or previous.type in CLOSING_BRACKETS)
+ ):
+ return DOT_PRIORITY
+
+ if (
+ leaf.type in MATH_OPERATORS
+ and leaf.parent
+ and leaf.parent.type not in {syms.factor, syms.star_expr}
+ ):
+ return MATH_PRIORITIES[leaf.type]
+
+ if leaf.type in COMPARATORS:
+ return COMPARATOR_PRIORITY
+
+ if (
+ leaf.type == token.STRING
+ and previous is not None
+ and previous.type == token.STRING
+ ):
+ return STRING_PRIORITY
+
+ if leaf.type not in {token.NAME, token.ASYNC}:
+ return 0
+
+ if (
+ leaf.value == "for"
+ and leaf.parent
+ and leaf.parent.type in {syms.comp_for, syms.old_comp_for}
+ or leaf.type == token.ASYNC
+ ):
+ if (
+ not isinstance(leaf.prev_sibling, Leaf)
+ or leaf.prev_sibling.value != "async"
+ ):
+ return COMPREHENSION_PRIORITY
+
+ if (
+ leaf.value == "if"
+ and leaf.parent
+ and leaf.parent.type in {syms.comp_if, syms.old_comp_if}
+ ):
+ return COMPREHENSION_PRIORITY
+
+ if leaf.value in {"if", "else"} and leaf.parent and leaf.parent.type == syms.test:
+ return TERNARY_PRIORITY
+
+ if leaf.value == "is":
+ return COMPARATOR_PRIORITY
+
+ if (
+ leaf.value == "in"
+ and leaf.parent
+ and leaf.parent.type in {syms.comp_op, syms.comparison}
+ and not (
+ previous is not None
+ and previous.type == token.NAME
+ and previous.value == "not"
+ )
+ ):
+ return COMPARATOR_PRIORITY
+
+ if (
+ leaf.value == "not"
+ and leaf.parent
+ and leaf.parent.type == syms.comp_op
+ and not (
+ previous is not None
+ and previous.type == token.NAME
+ and previous.value == "is"
+ )
+ ):
+ return COMPARATOR_PRIORITY
+
+ if leaf.value in LOGIC_OPERATORS and leaf.parent:
+ return LOGIC_PRIORITY
+
+ return 0
+
+
+FMT_OFF = {"# fmt: off", "# fmt:off", "# yapf: disable"}
+FMT_ON = {"# fmt: on", "# fmt:on", "# yapf: enable"}
+
+
+def generate_comments(leaf: LN) -> Iterator[Leaf]:
+ """Clean the prefix of the `leaf` and generate comments from it, if any.
+
+ Comments in lib2to3 are shoved into the whitespace prefix. This happens
+ in `pgen2/driver.py:Driver.parse_tokens()`. This was a brilliant implementation
+ move because it does away with modifying the grammar to include all the
+ possible places in which comments can be placed.
+
+ The sad consequence for us though is that comments don't "belong" anywhere.
+ This is why this function generates simple parentless Leaf objects for
+ comments. We simply don't know what the correct parent should be.
+
+ No matter though, we can live without this. We really only need to
+ differentiate between inline and standalone comments. The latter don't
+ share the line with any code.
+
+ Inline comments are emitted as regular token.COMMENT leaves. Standalone
+ are emitted with a fake STANDALONE_COMMENT token identifier.
+ """
+ for pc in list_comments(leaf.prefix, is_endmarker=leaf.type == token.ENDMARKER):
+ yield Leaf(pc.type, pc.value, prefix="\n" * pc.newlines)
+
+
+@dataclass
+class ProtoComment:
+ """Describes a piece of syntax that is a comment.
+
+ It's not a :class:`blib2to3.pytree.Leaf` so that:
+
+ * it can be cached (`Leaf` objects should not be reused more than once as
+ they store their lineno, column, prefix, and parent information);
+ * `newlines` and `consumed` fields are kept separate from the `value`. This
+ simplifies handling of special marker comments like ``# fmt: off/on``.
+ """
+
+ type: int # token.COMMENT or STANDALONE_COMMENT
+ value: str # content of the comment
+ newlines: int # how many newlines before the comment
+ consumed: int # how many characters of the original leaf's prefix did we consume
+
+
+@lru_cache(maxsize=4096)
+def list_comments(prefix: str, *, is_endmarker: bool) -> List[ProtoComment]:
+ """Return a list of :class:`ProtoComment` objects parsed from the given `prefix`."""
+ result: List[ProtoComment] = []
+ if not prefix or "#" not in prefix:
+ return result
+
+ consumed = 0
+ nlines = 0
+ ignored_lines = 0
+ for index, line in enumerate(prefix.split("\n")):
+ consumed += len(line) + 1 # adding the length of the split '\n'
+ line = line.lstrip()
+ if not line:
+ nlines += 1
+ if not line.startswith("#"):
+ # Escaped newlines outside of a comment are not really newlines at
+ # all. We treat a single-line comment following an escaped newline
+ # as a simple trailing comment.
+ if line.endswith("\\"):
+ ignored_lines += 1
+ continue
+
+ if index == ignored_lines and not is_endmarker:
+ comment_type = token.COMMENT # simple trailing comment
+ else:
+ comment_type = STANDALONE_COMMENT
+ comment = make_comment(line)
+ result.append(
+ ProtoComment(
+ type=comment_type, value=comment, newlines=nlines, consumed=consumed
+ )
+ )
+ nlines = 0
+ return result
+
+
+def make_comment(content: str) -> str:
+ """Return a consistently formatted comment from the given `content` string.
+
+ All comments (except for "##", "#!", "#:", '#'", "#%%") should have a single
+ space between the hash sign and the content.
+
+ If `content` didn't start with a hash sign, one is provided.
+ """
+ content = content.rstrip()
+ if not content:
+ return "#"
+
+ if content[0] == "#":
+ content = content[1:]
+ if content and content[0] not in " !:#'%":
+ content = " " + content
+ return "#" + content
+
+
+def split_line(
+ line: Line,
+ line_length: int,
+ inner: bool = False,
+ features: Collection[Feature] = (),
+) -> Iterator[Line]:
+ """Split a `line` into potentially many lines.
+
+ They should fit in the allotted `line_length` but might not be able to.
+ `inner` signifies that there were a pair of brackets somewhere around the
+ current `line`, possibly transitively. This means we can fallback to splitting
+ by delimiters if the LHS/RHS don't yield any results.
+
+ `features` are syntactical features that may be used in the output.
+ """
+ if line.is_comment:
+ yield line
+ return
+
+ line_str = str(line).strip("\n")
+
+ if (
+ not line.contains_uncollapsable_type_comments()
+ and not line.should_explode
+ and not line.is_collection_with_optional_trailing_comma
+ and (
+ is_line_short_enough(line, line_length=line_length, line_str=line_str)
+ or line.contains_unsplittable_type_ignore()
+ )
+ ):
+ yield line
+ return
+
+ split_funcs: List[SplitFunc]
+ if line.is_def:
+ split_funcs = [left_hand_split]
+ else:
+
+ def rhs(line: Line, features: Collection[Feature]) -> Iterator[Line]:
+ for omit in generate_trailers_to_omit(line, line_length):
+ lines = list(right_hand_split(line, line_length, features, omit=omit))
+ if is_line_short_enough(lines[0], line_length=line_length):
+ yield from lines
+ return
+
+ # All splits failed, best effort split with no omits.
+ # This mostly happens to multiline strings that are by definition
+ # reported as not fitting a single line.
+ yield from right_hand_split(line, line_length, features=features)
+
+ if line.inside_brackets:
+ split_funcs = [delimiter_split, standalone_comment_split, rhs]
+ else:
+ split_funcs = [rhs]
+ for split_func in split_funcs:
+ # We are accumulating lines in `result` because we might want to abort
+ # mission and return the original line in the end, or attempt a different
+ # split altogether.
+ result: List[Line] = []
+ try:
+ for l in split_func(line, features):
+ if str(l).strip("\n") == line_str:
+ raise CannotSplit("Split function returned an unchanged result")
+
+ result.extend(
+ split_line(
+ l, line_length=line_length, inner=True, features=features
+ )
+ )
+ except CannotSplit:
+ continue
+
+ else:
+ yield from result
+ break
+
+ else:
+ yield line
+
+
+def left_hand_split(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
+ """Split line into many lines, starting with the first matching bracket pair.
+
+ Note: this usually looks weird, only use this for function definitions.
+ Prefer RHS otherwise. This is why this function is not symmetrical with
+ :func:`right_hand_split` which also handles optional parentheses.
+ """
+ tail_leaves: List[Leaf] = []
+ body_leaves: List[Leaf] = []
+ head_leaves: List[Leaf] = []
+ current_leaves = head_leaves
+ matching_bracket = None
+ for leaf in line.leaves:
+ if (
+ current_leaves is body_leaves
+ and leaf.type in CLOSING_BRACKETS
+ and leaf.opening_bracket is matching_bracket
+ ):
+ current_leaves = tail_leaves if body_leaves else head_leaves
+ current_leaves.append(leaf)
+ if current_leaves is head_leaves:
+ if leaf.type in OPENING_BRACKETS:
+ matching_bracket = leaf
+ current_leaves = body_leaves
+ if not matching_bracket:
+ raise CannotSplit("No brackets found")
+
+ head = bracket_split_build_line(head_leaves, line, matching_bracket)
+ body = bracket_split_build_line(body_leaves, line, matching_bracket, is_body=True)
+ tail = bracket_split_build_line(tail_leaves, line, matching_bracket)
+ bracket_split_succeeded_or_raise(head, body, tail)
+ for result in (head, body, tail):
+ if result:
+ yield result
+
+
+def right_hand_split(
+ line: Line,
+ line_length: int,
+ features: Collection[Feature] = (),
+ omit: Collection[LeafID] = (),
+) -> Iterator[Line]:
+ """Split line into many lines, starting with the last matching bracket pair.
+
+ If the split was by optional parentheses, attempt splitting without them, too.
+ `omit` is a collection of closing bracket IDs that shouldn't be considered for
+ this split.
+
+ Note: running this function modifies `bracket_depth` on the leaves of `line`.
+ """
+ tail_leaves: List[Leaf] = []
+ body_leaves: List[Leaf] = []
+ head_leaves: List[Leaf] = []
+ current_leaves = tail_leaves
+ opening_bracket = None
+ closing_bracket = None
+ for leaf in reversed(line.leaves):
+ if current_leaves is body_leaves:
+ if leaf is opening_bracket:
+ current_leaves = head_leaves if body_leaves else tail_leaves
+ current_leaves.append(leaf)
+ if current_leaves is tail_leaves:
+ if leaf.type in CLOSING_BRACKETS and id(leaf) not in omit:
+ opening_bracket = leaf.opening_bracket
+ closing_bracket = leaf
+ current_leaves = body_leaves
+ if not (opening_bracket and closing_bracket and head_leaves):
+ # If there is no opening or closing_bracket that means the split failed and
+ # all content is in the tail. Otherwise, if `head_leaves` are empty, it means
+ # the matching `opening_bracket` wasn't available on `line` anymore.
+ raise CannotSplit("No brackets found")
+
+ tail_leaves.reverse()
+ body_leaves.reverse()
+ head_leaves.reverse()
+ head = bracket_split_build_line(head_leaves, line, opening_bracket)
+ body = bracket_split_build_line(body_leaves, line, opening_bracket, is_body=True)
+ tail = bracket_split_build_line(tail_leaves, line, opening_bracket)
+ bracket_split_succeeded_or_raise(head, body, tail)
+ if (
+ # the body shouldn't be exploded
+ not body.should_explode
+ # the opening bracket is an optional paren
+ and opening_bracket.type == token.LPAR
+ and not opening_bracket.value
+ # the closing bracket is an optional paren
+ and closing_bracket.type == token.RPAR
+ and not closing_bracket.value
+ # it's not an import (optional parens are the only thing we can split on
+ # in this case; attempting a split without them is a waste of time)
+ and not line.is_import
+ # there are no standalone comments in the body
+ and not body.contains_standalone_comments(0)
+ # and we can actually remove the parens
+ and can_omit_invisible_parens(body, line_length)
+ ):
+ omit = {id(closing_bracket), *omit}
+ try:
+ yield from right_hand_split(line, line_length, features=features, omit=omit)
+ return
+
+ except CannotSplit:
+ if not (
+ can_be_split(body)
+ or is_line_short_enough(body, line_length=line_length)
+ ):
+ raise CannotSplit(
+ "Splitting failed, body is still too long and can't be split."
+ )
+
+ elif head.contains_multiline_strings() or tail.contains_multiline_strings():
+ raise CannotSplit(
+ "The current optional pair of parentheses is bound to fail to "
+ "satisfy the splitting algorithm because the head or the tail "
+ "contains multiline strings which by definition never fit one "
+ "line."
+ )
+
+ ensure_visible(opening_bracket)
+ ensure_visible(closing_bracket)
+ for result in (head, body, tail):
+ if result:
+ yield result
+
+
+def bracket_split_succeeded_or_raise(head: Line, body: Line, tail: Line) -> None:
+ """Raise :exc:`CannotSplit` if the last left- or right-hand split failed.
+
+ Do nothing otherwise.
+
+ A left- or right-hand split is based on a pair of brackets. Content before
+ (and including) the opening bracket is left on one line, content inside the
+ brackets is put on a separate line, and finally content starting with and
+ following the closing bracket is put on a separate line.
+
+ Those are called `head`, `body`, and `tail`, respectively. If the split
+ produced the same line (all content in `head`) or ended up with an empty `body`
+ and the `tail` is just the closing bracket, then it's considered failed.
+ """
+ tail_len = len(str(tail).strip())
+ if not body:
+ if tail_len == 0:
+ raise CannotSplit("Splitting brackets produced the same line")
+
+ elif tail_len < 3:
+ raise CannotSplit(
+ f"Splitting brackets on an empty body to save "
+ f"{tail_len} characters is not worth it"
+ )
+
+
+def bracket_split_build_line(
+ leaves: List[Leaf], original: Line, opening_bracket: Leaf, *, is_body: bool = False
+) -> Line:
+ """Return a new line with given `leaves` and respective comments from `original`.
+
+ If `is_body` is True, the result line is one-indented inside brackets and as such
+ has its first leaf's prefix normalized and a trailing comma added when expected.
+ """
+ result = Line(depth=original.depth)
+ if is_body:
+ result.inside_brackets = True
+ result.depth += 1
+ if leaves:
+ # Since body is a new indent level, remove spurious leading whitespace.
+ normalize_prefix(leaves[0], inside_brackets=True)
+ # Ensure a trailing comma for imports and standalone function arguments, but
+ # be careful not to add one after any comments.
+ no_commas = original.is_def and not any(
+ l.type == token.COMMA for l in leaves
+ )
+
+ if original.is_import or no_commas:
+ for i in range(len(leaves) - 1, -1, -1):
+ if leaves[i].type == STANDALONE_COMMENT:
+ continue
+ elif leaves[i].type == token.COMMA:
+ break
+ else:
+ leaves.insert(i + 1, Leaf(token.COMMA, ","))
+ break
+ # Populate the line
+ for leaf in leaves:
+ result.append(leaf, preformatted=True)
+ for comment_after in original.comments_after(leaf):
+ result.append(comment_after, preformatted=True)
+ if is_body:
+ result.should_explode = should_explode(result, opening_bracket)
+ return result
+
+
+def dont_increase_indentation(split_func: SplitFunc) -> SplitFunc:
+ """Normalize prefix of the first leaf in every line returned by `split_func`.
+
+ This is a decorator over relevant split functions.
+ """
+
+ @wraps(split_func)
+ def split_wrapper(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
+ for l in split_func(line, features):
+ normalize_prefix(l.leaves[0], inside_brackets=True)
+ yield l
+
+ return split_wrapper
+
+
+@dont_increase_indentation
+def delimiter_split(line: Line, features: Collection[Feature] = ()) -> Iterator[Line]:
+ """Split according to delimiters of the highest priority.
+
+ If the appropriate Features are given, the split will add trailing commas
+ also in function signatures and calls that contain `*` and `**`.
+ """
+ try:
+ last_leaf = line.leaves[-1]
+ except IndexError:
+ raise CannotSplit("Line empty")
+
+ bt = line.bracket_tracker
+ try:
+ delimiter_priority = bt.max_delimiter_priority(exclude={id(last_leaf)})
+ except ValueError:
+ raise CannotSplit("No delimiters found")
+
+ if delimiter_priority == DOT_PRIORITY:
+ if bt.delimiter_count_with_priority(delimiter_priority) == 1:
+ raise CannotSplit("Splitting a single attribute from its owner looks wrong")
+
+ current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
+ lowest_depth = sys.maxsize
+ trailing_comma_safe = True
+
+ def append_to_line(leaf: Leaf) -> Iterator[Line]:
+ """Append `leaf` to current line or to new line if appending impossible."""
+ nonlocal current_line
+ try:
+ current_line.append_safe(leaf, preformatted=True)
+ except ValueError:
+ yield current_line
+
+ current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
+ current_line.append(leaf)
+
+ for leaf in line.leaves:
+ yield from append_to_line(leaf)
+
+ for comment_after in line.comments_after(leaf):
+ yield from append_to_line(comment_after)
+
+ lowest_depth = min(lowest_depth, leaf.bracket_depth)
+ if leaf.bracket_depth == lowest_depth:
+ if is_vararg(leaf, within={syms.typedargslist}):
+ trailing_comma_safe = (
+ trailing_comma_safe and Feature.TRAILING_COMMA_IN_DEF in features
+ )
+ elif is_vararg(leaf, within={syms.arglist, syms.argument}):
+ trailing_comma_safe = (
+ trailing_comma_safe and Feature.TRAILING_COMMA_IN_CALL in features
+ )
+
+ leaf_priority = bt.delimiters.get(id(leaf))
+ if leaf_priority == delimiter_priority:
+ yield current_line
+
+ current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
+ if current_line:
+ if (
+ trailing_comma_safe
+ and delimiter_priority == COMMA_PRIORITY
+ and current_line.leaves[-1].type != token.COMMA
+ and current_line.leaves[-1].type != STANDALONE_COMMENT
+ ):
+ current_line.append(Leaf(token.COMMA, ","))
+ yield current_line
+
+
+@dont_increase_indentation
+def standalone_comment_split(
+ line: Line, features: Collection[Feature] = ()
+) -> Iterator[Line]:
+ """Split standalone comments from the rest of the line."""
+ if not line.contains_standalone_comments(0):
+ raise CannotSplit("Line does not have any standalone comments")
+
+ current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
+
+ def append_to_line(leaf: Leaf) -> Iterator[Line]:
+ """Append `leaf` to current line or to new line if appending impossible."""
+ nonlocal current_line
+ try:
+ current_line.append_safe(leaf, preformatted=True)
+ except ValueError:
+ yield current_line
+
+ current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
+ current_line.append(leaf)
+
+ for leaf in line.leaves:
+ yield from append_to_line(leaf)
+
+ for comment_after in line.comments_after(leaf):
+ yield from append_to_line(comment_after)
+
+ if current_line:
+ yield current_line
+
+
+def is_import(leaf: Leaf) -> bool:
+ """Return True if the given leaf starts an import statement."""
+ p = leaf.parent
+ t = leaf.type
+ v = leaf.value
+ return bool(
+ t == token.NAME
+ and (
+ (v == "import" and p and p.type == syms.import_name)
+ or (v == "from" and p and p.type == syms.import_from)
+ )
+ )
+
+
+def is_type_comment(leaf: Leaf, suffix: str = "") -> bool:
+ """Return True if the given leaf is a special comment.
+ Only returns true for type comments for now."""
+ t = leaf.type
+ v = leaf.value
+ return t in {token.COMMENT, t == STANDALONE_COMMENT} and v.startswith(
+ "# type:" + suffix
+ )
+
+
+def normalize_prefix(leaf: Leaf, *, inside_brackets: bool) -> None:
+ """Leave existing extra newlines if not `inside_brackets`. Remove everything
+ else.
+
+ Note: don't use backslashes for formatting or you'll lose your voting rights.
+ """
+ if not inside_brackets:
+ spl = leaf.prefix.split("#")
+ if "\\" not in spl[0]:
+ nl_count = spl[-1].count("\n")
+ if len(spl) > 1:
+ nl_count -= 1
+ leaf.prefix = "\n" * nl_count
+ return
+
+ leaf.prefix = ""
+
+
+def normalize_string_prefix(leaf: Leaf, remove_u_prefix: bool = False) -> None:
+ """Make all string prefixes lowercase.
+
+ If remove_u_prefix is given, also removes any u prefix from the string.
+
+ Note: Mutates its argument.
+ """
+ match = re.match(r"^([furbFURB]*)(.*)$", leaf.value, re.DOTALL)
+ assert match is not None, f"failed to match string {leaf.value!r}"
+ orig_prefix = match.group(1)
+ new_prefix = orig_prefix.lower()
+ if remove_u_prefix:
+ new_prefix = new_prefix.replace("u", "")
+ leaf.value = f"{new_prefix}{match.group(2)}"
+
+
+def normalize_string_quotes(leaf: Leaf) -> None:
+ """Prefer double quotes but only if it doesn't cause more escaping.
+
+ Adds or removes backslashes as appropriate. Doesn't parse and fix
+ strings nested in f-strings (yet).
+
+ Note: Mutates its argument.
+ """
+ value = leaf.value.lstrip("furbFURB")
+ if value[:3] == '"""':
+ return
+
+ elif value[:3] == "'''":
+ orig_quote = "'''"
+ new_quote = '"""'
+ elif value[0] == '"':
+ orig_quote = '"'
+ new_quote = "'"
+ else:
+ orig_quote = "'"
+ new_quote = '"'
+ first_quote_pos = leaf.value.find(orig_quote)
+ if first_quote_pos == -1:
+ return # There's an internal error
+
+ prefix = leaf.value[:first_quote_pos]
+ unescaped_new_quote = re.compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
+ escaped_new_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){new_quote}")
+ escaped_orig_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){orig_quote}")
+ body = leaf.value[first_quote_pos + len(orig_quote) : -len(orig_quote)]
+ if "r" in prefix.casefold():
+ if unescaped_new_quote.search(body):
+ # There's at least one unescaped new_quote in this raw string
+ # so converting is impossible
+ return
+
+ # Do not introduce or remove backslashes in raw strings
+ new_body = body
+ else:
+ # remove unnecessary escapes
+ new_body = sub_twice(escaped_new_quote, rf"\1\2{new_quote}", body)
+ if body != new_body:
+ # Consider the string without unnecessary escapes as the original
+ body = new_body
+ leaf.value = f"{prefix}{orig_quote}{body}{orig_quote}"
+ new_body = sub_twice(escaped_orig_quote, rf"\1\2{orig_quote}", new_body)
+ new_body = sub_twice(unescaped_new_quote, rf"\1\\{new_quote}", new_body)
+ if "f" in prefix.casefold():
+ matches = re.findall(
+ r"""
+ (?:[^{]|^)\{ # start of the string or a non-{ followed by a single {
+ ([^{].*?) # contents of the brackets except if begins with {{
+ \}(?:[^}]|$) # A } followed by end of the string or a non-}
+ """,
+ new_body,
+ re.VERBOSE,
+ )
+ for m in matches:
+ if "\\" in str(m):
+ # Do not introduce backslashes in interpolated expressions
+ return
+ if new_quote == '"""' and new_body[-1:] == '"':
+ # edge case:
+ new_body = new_body[:-1] + '\\"'
+ orig_escape_count = body.count("\\")
+ new_escape_count = new_body.count("\\")
+ if new_escape_count > orig_escape_count:
+ return # Do not introduce more escaping
+
+ if new_escape_count == orig_escape_count and orig_quote == '"':
+ return # Prefer double quotes
+
+ leaf.value = f"{prefix}{new_quote}{new_body}{new_quote}"
+
+
+def normalize_numeric_literal(leaf: Leaf) -> None:
+ """Normalizes numeric (float, int, and complex) literals.
+
+ All letters used in the representation are normalized to lowercase (except
+ in Python 2 long literals).
+ """
+ text = leaf.value.lower()
+ if text.startswith(("0o", "0b")):
+ # Leave octal and binary literals alone.
+ pass
+ elif text.startswith("0x"):
+ # Change hex literals to upper case.
+ before, after = text[:2], text[2:]
+ text = f"{before}{after.upper()}"
+ elif "e" in text:
+ before, after = text.split("e")
+ sign = ""
+ if after.startswith("-"):
+ after = after[1:]
+ sign = "-"
+ elif after.startswith("+"):
+ after = after[1:]
+ before = format_float_or_int_string(before)
+ text = f"{before}e{sign}{after}"
+ elif text.endswith(("j", "l")):
+ number = text[:-1]
+ suffix = text[-1]
+ # Capitalize in "2L" because "l" looks too similar to "1".
+ if suffix == "l":
+ suffix = "L"
+ text = f"{format_float_or_int_string(number)}{suffix}"
+ else:
+ text = format_float_or_int_string(text)
+ leaf.value = text
+
+
+def format_float_or_int_string(text: str) -> str:
+ """Formats a float string like "1.0"."""
+ if "." not in text:
+ return text
+
+ before, after = text.split(".")
+ return f"{before or 0}.{after or 0}"
+
+
+def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
+ """Make existing optional parentheses invisible or create new ones.
+
+ `parens_after` is a set of string leaf values immediately after which parens
+ should be put.
+
+ Standardizes on visible parentheses for single-element tuples, and keeps
+ existing visible parentheses for other tuples and generator expressions.
+ """
+ for pc in list_comments(node.prefix, is_endmarker=False):
+ if pc.value in FMT_OFF:
+ # This `node` has a prefix with `# fmt: off`, don't mess with parens.
+ return
+
+ check_lpar = False
+ for index, child in enumerate(list(node.children)):
+ # Add parentheses around long tuple unpacking in assignments.
+ if (
+ index == 0
+ and isinstance(child, Node)
+ and child.type == syms.testlist_star_expr
+ ):
+ check_lpar = True
+
+ if check_lpar:
+ if is_walrus_assignment(child):
+ continue
+ if child.type == syms.atom:
+ # Determines if the underlying atom should be surrounded with
+ # invisible params - also makes parens invisible recursively
+ # within the atom and removes repeated invisible parens within
+ # the atom
+ should_surround_with_parens = maybe_make_parens_invisible_in_atom(
+ child, parent=node
+ )
+
+ if should_surround_with_parens:
+ lpar = Leaf(token.LPAR, "")
+ rpar = Leaf(token.RPAR, "")
+ index = child.remove() or 0
+ node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
+ elif is_one_tuple(child):
+ # wrap child in visible parentheses
+ lpar = Leaf(token.LPAR, "(")
+ rpar = Leaf(token.RPAR, ")")
+ child.remove()
+ node.insert_child(index, Node(syms.atom, [lpar, child, rpar]))
+ elif node.type == syms.import_from:
+ # "import from" nodes store parentheses directly as part of
+ # the statement
+ if child.type == token.LPAR:
+ # make parentheses invisible
+ child.value = "" # type: ignore
+ node.children[-1].value = "" # type: ignore
+ elif child.type != token.STAR:
+ # insert invisible parentheses
+ node.insert_child(index, Leaf(token.LPAR, ""))
+ node.append_child(Leaf(token.RPAR, ""))
+ break
+
+ elif not (isinstance(child, Leaf) and is_multiline_string(child)):
+ # wrap child in invisible parentheses
+ lpar = Leaf(token.LPAR, "")
+ rpar = Leaf(token.RPAR, "")
+ index = child.remove() or 0
+ prefix = child.prefix
+ child.prefix = ""
+ new_child = Node(syms.atom, [lpar, child, rpar])
+ new_child.prefix = prefix
+ node.insert_child(index, new_child)
+
+ check_lpar = isinstance(child, Leaf) and child.value in parens_after
+
+
+def normalize_fmt_off(node: Node) -> None:
+ """Convert content between `# fmt: off`/`# fmt: on` into standalone comments."""
+ try_again = True
+ while try_again:
+ try_again = convert_one_fmt_off_pair(node)
+
+
+def convert_one_fmt_off_pair(node: Node) -> bool:
+ """Convert content of a single `# fmt: off`/`# fmt: on` into a standalone comment.
+
+ Returns True if a pair was converted.
+ """
+ for leaf in node.leaves():
+ previous_consumed = 0
+ for comment in list_comments(leaf.prefix, is_endmarker=False):
+ if comment.value in FMT_OFF:
+ # We only want standalone comments. If there's no previous leaf or
+ # the previous leaf is indentation, it's a standalone comment in
+ # disguise.
+ if comment.type != STANDALONE_COMMENT:
+ prev = preceding_leaf(leaf)
+ if prev and prev.type not in WHITESPACE:
+ continue
+
+ ignored_nodes = list(generate_ignored_nodes(leaf))
+ if not ignored_nodes:
+ continue
+
+ first = ignored_nodes[0] # Can be a container node with the `leaf`.
+ parent = first.parent
+ prefix = first.prefix
+ first.prefix = prefix[comment.consumed :]
+ hidden_value = (
+ comment.value + "\n" + "".join(str(n) for n in ignored_nodes)
+ )
+ if hidden_value.endswith("\n"):
+ # That happens when one of the `ignored_nodes` ended with a NEWLINE
+ # leaf (possibly followed by a DEDENT).
+ hidden_value = hidden_value[:-1]
+ first_idx = None
+ for ignored in ignored_nodes:
+ index = ignored.remove()
+ if first_idx is None:
+ first_idx = index
+ assert parent is not None, "INTERNAL ERROR: fmt: on/off handling (1)"
+ assert first_idx is not None, "INTERNAL ERROR: fmt: on/off handling (2)"
+ parent.insert_child(
+ first_idx,
+ Leaf(
+ STANDALONE_COMMENT,
+ hidden_value,
+ prefix=prefix[:previous_consumed] + "\n" * comment.newlines,
+ ),
+ )
+ return True
+
+ previous_consumed = comment.consumed
+
+ return False
+
+
+def generate_ignored_nodes(leaf: Leaf) -> Iterator[LN]:
+ """Starting from the container of `leaf`, generate all leaves until `# fmt: on`.
+
+ Stops at the end of the block.
+ """
+ container: Optional[LN] = container_of(leaf)
+ while container is not None and container.type != token.ENDMARKER:
+ for comment in list_comments(container.prefix, is_endmarker=False):
+ if comment.value in FMT_ON:
+ return
+
+ yield container
+
+ container = container.next_sibling
+
+
+def maybe_make_parens_invisible_in_atom(node: LN, parent: LN) -> bool:
+ """If it's safe, make the parens in the atom `node` invisible, recursively.
+ Additionally, remove repeated, adjacent invisible parens from the atom `node`
+ as they are redundant.
+
+ Returns whether the node should itself be wrapped in invisible parentheses.
+
+ """
+ if (
+ node.type != syms.atom
+ or is_empty_tuple(node)
+ or is_one_tuple(node)
+ or (is_yield(node) and parent.type != syms.expr_stmt)
+ or max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
+ ):
+ return False
+
+ first = node.children[0]
+ last = node.children[-1]
+ if first.type == token.LPAR and last.type == token.RPAR:
+ middle = node.children[1]
+ # make parentheses invisible
+ first.value = "" # type: ignore
+ last.value = "" # type: ignore
+ maybe_make_parens_invisible_in_atom(middle, parent=parent)
+
+ if is_atom_with_invisible_parens(middle):
+ # Strip the invisible parens from `middle` by replacing
+ # it with the child in-between the invisible parens
+ middle.replace(middle.children[1])
+
+ return False
+
+ return True
+
+
+def is_atom_with_invisible_parens(node: LN) -> bool:
+ """Given a `LN`, determines whether it's an atom `node` with invisible
+ parens. Useful in dedupe-ing and normalizing parens.
+ """
+ if isinstance(node, Leaf) or node.type != syms.atom:
+ return False
+
+ first, last = node.children[0], node.children[-1]
+ return (
+ isinstance(first, Leaf)
+ and first.type == token.LPAR
+ and first.value == ""
+ and isinstance(last, Leaf)
+ and last.type == token.RPAR
+ and last.value == ""
+ )
+
+
+def is_empty_tuple(node: LN) -> bool:
+ """Return True if `node` holds an empty tuple."""
+ return (
+ node.type == syms.atom
+ and len(node.children) == 2
+ and node.children[0].type == token.LPAR
+ and node.children[1].type == token.RPAR
+ )
+
+
+def unwrap_singleton_parenthesis(node: LN) -> Optional[LN]:
+ """Returns `wrapped` if `node` is of the shape ( wrapped ).
+
+ Parenthesis can be optional. Returns None otherwise"""
+ if len(node.children) != 3:
+ return None
+ lpar, wrapped, rpar = node.children
+ if not (lpar.type == token.LPAR and rpar.type == token.RPAR):
+ return None
+
+ return wrapped
+
+
+def is_one_tuple(node: LN) -> bool:
+ """Return True if `node` holds a tuple with one element, with or without parens."""
+ if node.type == syms.atom:
+ gexp = unwrap_singleton_parenthesis(node)
+ if gexp is None or gexp.type != syms.testlist_gexp:
+ return False
+
+ return len(gexp.children) == 2 and gexp.children[1].type == token.COMMA
+
+ return (
+ node.type in IMPLICIT_TUPLE
+ and len(node.children) == 2
+ and node.children[1].type == token.COMMA
+ )
+
+
+def is_walrus_assignment(node: LN) -> bool:
+ """Return True iff `node` is of the shape ( test := test )"""
+ inner = unwrap_singleton_parenthesis(node)
+ return inner is not None and inner.type == syms.namedexpr_test
+
+
+def is_yield(node: LN) -> bool:
+ """Return True if `node` holds a `yield` or `yield from` expression."""
+ if node.type == syms.yield_expr:
+ return True
+
+ if node.type == token.NAME and node.value == "yield": # type: ignore
+ return True
+
+ if node.type != syms.atom:
+ return False
+
+ if len(node.children) != 3:
+ return False
+
+ lpar, expr, rpar = node.children
+ if lpar.type == token.LPAR and rpar.type == token.RPAR:
+ return is_yield(expr)
+
+ return False
+
+
+def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
+ """Return True if `leaf` is a star or double star in a vararg or kwarg.
+
+ If `within` includes VARARGS_PARENTS, this applies to function signatures.
+ If `within` includes UNPACKING_PARENTS, it applies to right hand-side
+ extended iterable unpacking (PEP 3132) and additional unpacking
+ generalizations (PEP 448).
+ """
+ if leaf.type not in VARARGS_SPECIALS or not leaf.parent:
+ return False
+
+ p = leaf.parent
+ if p.type == syms.star_expr:
+ # Star expressions are also used as assignment targets in extended
+ # iterable unpacking (PEP 3132). See what its parent is instead.
+ if not p.parent:
+ return False
+
+ p = p.parent
+
+ return p.type in within
+
+
+def is_multiline_string(leaf: Leaf) -> bool:
+ """Return True if `leaf` is a multiline string that actually spans many lines."""
+ value = leaf.value.lstrip("furbFURB")
+ return value[:3] in {'"""', "'''"} and "\n" in value
+
+
+def is_stub_suite(node: Node) -> bool:
+ """Return True if `node` is a suite with a stub body."""
+ if (
+ len(node.children) != 4
+ or node.children[0].type != token.NEWLINE
+ or node.children[1].type != token.INDENT
+ or node.children[3].type != token.DEDENT
+ ):
+ return False
+
+ return is_stub_body(node.children[2])
+
+
+def is_stub_body(node: LN) -> bool:
+ """Return True if `node` is a simple statement containing an ellipsis."""
+ if not isinstance(node, Node) or node.type != syms.simple_stmt:
+ return False
+
+ if len(node.children) != 2:
+ return False
+
+ child = node.children[0]
+ return (
+ child.type == syms.atom
+ and len(child.children) == 3
+ and all(leaf == Leaf(token.DOT, ".") for leaf in child.children)
+ )
+
+
+def max_delimiter_priority_in_atom(node: LN) -> Priority:
+ """Return maximum delimiter priority inside `node`.
+
+ This is specific to atoms with contents contained in a pair of parentheses.
+ If `node` isn't an atom or there are no enclosing parentheses, returns 0.
+ """
+ if node.type != syms.atom:
+ return 0
+
+ first = node.children[0]
+ last = node.children[-1]
+ if not (first.type == token.LPAR and last.type == token.RPAR):
+ return 0
+
+ bt = BracketTracker()
+ for c in node.children[1:-1]:
+ if isinstance(c, Leaf):
+ bt.mark(c)
+ else:
+ for leaf in c.leaves():
+ bt.mark(leaf)
+ try:
+ return bt.max_delimiter_priority()
+
+ except ValueError:
+ return 0
+
+
+def ensure_visible(leaf: Leaf) -> None:
+ """Make sure parentheses are visible.
+
+ They could be invisible as part of some statements (see
+ :func:`normalize_invisible_parens` and :func:`visit_import_from`).
+ """
+ if leaf.type == token.LPAR:
+ leaf.value = "("
+ elif leaf.type == token.RPAR:
+ leaf.value = ")"
+
+
+def should_explode(line: Line, opening_bracket: Leaf) -> bool:
+ """Should `line` immediately be split with `delimiter_split()` after RHS?"""
+
+ if not (
+ opening_bracket.parent
+ and opening_bracket.parent.type in {syms.atom, syms.import_from}
+ and opening_bracket.value in "[{("
+ ):
+ return False
+
+ try:
+ last_leaf = line.leaves[-1]
+ exclude = {id(last_leaf)} if last_leaf.type == token.COMMA else set()
+ max_priority = line.bracket_tracker.max_delimiter_priority(exclude=exclude)
+ except (IndexError, ValueError):
+ return False
+
+ return max_priority == COMMA_PRIORITY
+
+
+def get_features_used(node: Node) -> Set[Feature]:
+ """Return a set of (relatively) new Python features used in this file.
+
+ Currently looking for:
+ - f-strings;
+ - underscores in numeric literals;
+ - trailing commas after * or ** in function signatures and calls;
+ - positional only arguments in function signatures and lambdas;
+ """
+ features: Set[Feature] = set()
+ for n in node.pre_order():
+ if n.type == token.STRING:
+ value_head = n.value[:2] # type: ignore
+ if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}:
+ features.add(Feature.F_STRINGS)
+
+ elif n.type == token.NUMBER:
+ if "_" in n.value: # type: ignore
+ features.add(Feature.NUMERIC_UNDERSCORES)
+
+ elif n.type == token.SLASH:
+ if n.parent and n.parent.type in {syms.typedargslist, syms.arglist}:
+ features.add(Feature.POS_ONLY_ARGUMENTS)
+
+ elif n.type == token.COLONEQUAL:
+ features.add(Feature.ASSIGNMENT_EXPRESSIONS)
+
+ elif (
+ n.type in {syms.typedargslist, syms.arglist}
+ and n.children
+ and n.children[-1].type == token.COMMA
+ ):
+ if n.type == syms.typedargslist:
+ feature = Feature.TRAILING_COMMA_IN_DEF
+ else:
+ feature = Feature.TRAILING_COMMA_IN_CALL
+
+ for ch in n.children:
+ if ch.type in STARS:
+ features.add(feature)
+
+ if ch.type == syms.argument:
+ for argch in ch.children:
+ if argch.type in STARS:
+ features.add(feature)
+
+ return features
+
+
+def detect_target_versions(node: Node) -> Set[TargetVersion]:
+ """Detect the version to target based on the nodes used."""
+ features = get_features_used(node)
+ return {
+ version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
+ }
+
+
+def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[Set[LeafID]]:
+ """Generate sets of closing bracket IDs that should be omitted in a RHS.
+
+ Brackets can be omitted if the entire trailer up to and including
+ a preceding closing bracket fits in one line.
+
+ Yielded sets are cumulative (contain results of previous yields, too). First
+ set is empty.
+ """
+
+ omit: Set[LeafID] = set()
+ yield omit
+
+ length = 4 * line.depth
+ opening_bracket = None
+ closing_bracket = None
+ inner_brackets: Set[LeafID] = set()
+ for index, leaf, leaf_length in enumerate_with_length(line, reversed=True):
+ length += leaf_length
+ if length > line_length:
+ break
+
+ has_inline_comment = leaf_length > len(leaf.value) + len(leaf.prefix)
+ if leaf.type == STANDALONE_COMMENT or has_inline_comment:
+ break
+
+ if opening_bracket:
+ if leaf is opening_bracket:
+ opening_bracket = None
+ elif leaf.type in CLOSING_BRACKETS:
+ inner_brackets.add(id(leaf))
+ elif leaf.type in CLOSING_BRACKETS:
+ if index > 0 and line.leaves[index - 1].type in OPENING_BRACKETS:
+ # Empty brackets would fail a split so treat them as "inner"
+ # brackets (e.g. only add them to the `omit` set if another
+ # pair of brackets was good enough.
+ inner_brackets.add(id(leaf))
+ continue
+
+ if closing_bracket:
+ omit.add(id(closing_bracket))
+ omit.update(inner_brackets)
+ inner_brackets.clear()
+ yield omit
+
+ if leaf.value:
+ opening_bracket = leaf.opening_bracket
+ closing_bracket = leaf
+
+
+def get_future_imports(node: Node) -> Set[str]:
+ """Return a set of __future__ imports in the file."""
+ imports: Set[str] = set()
+
+ def get_imports_from_children(children: List[LN]) -> Generator[str, None, None]:
+ for child in children:
+ if isinstance(child, Leaf):
+ if child.type == token.NAME:
+ yield child.value
+ elif child.type == syms.import_as_name:
+ orig_name = child.children[0]
+ assert isinstance(orig_name, Leaf), "Invalid syntax parsing imports"
+ assert orig_name.type == token.NAME, "Invalid syntax parsing imports"
+ yield orig_name.value
+ elif child.type == syms.import_as_names:
+ yield from get_imports_from_children(child.children)
+ else:
+ raise AssertionError("Invalid syntax parsing imports")
+
+ for child in node.children:
+ if child.type != syms.simple_stmt:
+ break
+ first_child = child.children[0]
+ if isinstance(first_child, Leaf):
+ # Continue looking if we see a docstring; otherwise stop.
+ if (
+ len(child.children) == 2
+ and first_child.type == token.STRING
+ and child.children[1].type == token.NEWLINE
+ ):
+ continue
+ else:
+ break
+ elif first_child.type == syms.import_from:
+ module_name = first_child.children[1]
+ if not isinstance(module_name, Leaf) or module_name.value != "__future__":
+ break
+ imports |= set(get_imports_from_children(first_child.children[3:]))
+ else:
+ break
+ return imports
+
+
+def gen_python_files_in_dir(
+ path: Path,
+ root: Path,
+ include: Pattern[str],
+ exclude: Pattern[str],
+ report: "Report",
+) -> Iterator[Path]:
+ """Generate all files under `path` whose paths are not excluded by the
+ `exclude` regex, but are included by the `include` regex.
+
+ Symbolic links pointing outside of the `root` directory are ignored.
+
+ `report` is where output about exclusions goes.
+ """
+ assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
+ for child in path.iterdir():
+ try:
+ normalized_path = "/" + child.resolve().relative_to(root).as_posix()
+ except ValueError:
+ if child.is_symlink():
+ report.path_ignored(
+ child, f"is a symbolic link that points outside {root}"
+ )
+ continue
+
+ raise
+
+ if child.is_dir():
+ normalized_path += "/"
+ exclude_match = exclude.search(normalized_path)
+ if exclude_match and exclude_match.group(0):
+ report.path_ignored(child, f"matches the --exclude regular expression")
+ continue
+
+ if child.is_dir():
+ yield from gen_python_files_in_dir(child, root, include, exclude, report)
+
+ elif child.is_file():
+ include_match = include.search(normalized_path)
+ if include_match:
+ yield child
+
+
+@lru_cache()
+def find_project_root(srcs: Iterable[str]) -> Path:
+ """Return a directory containing .git, .hg, or pyproject.toml.
+
+ That directory can be one of the directories passed in `srcs` or their
+ common parent.
+
+ If no directory in the tree contains a marker that would specify it's the
+ project root, the root of the file system is returned.
+ """
+ if not srcs:
+ return Path("/").resolve()
+
+ common_base = min(Path(src).resolve() for src in srcs)
+ if common_base.is_dir():
+ # Append a fake file so `parents` below returns `common_base_dir`, too.
+ common_base /= "fake-file"
+ for directory in common_base.parents:
+ if (directory / ".git").is_dir():
+ return directory
+
+ if (directory / ".hg").is_dir():
+ return directory
+
+ if (directory / "pyproject.toml").is_file():
+ return directory
+
+ return directory
+
+
+@dataclass
+class Report:
+ """Provides a reformatting counter. Can be rendered with `str(report)`."""
+
+ check: bool = False
+ quiet: bool = False
+ verbose: bool = False
+ change_count: int = 0
+ same_count: int = 0
+ failure_count: int = 0
+
+ def done(self, src: Path, changed: Changed) -> None:
+ """Increment the counter for successful reformatting. Write out a message."""
+ if changed is Changed.YES:
+ reformatted = "would reformat" if self.check else "reformatted"
+ if self.verbose or not self.quiet:
+ out(f"{reformatted} {src}")
+ self.change_count += 1
+ else:
+ if self.verbose:
+ if changed is Changed.NO:
+ msg = f"{src} already well formatted, good job."
+ else:
+ msg = f"{src} wasn't modified on disk since last run."
+ out(msg, bold=False)
+ self.same_count += 1
+
+ def failed(self, src: Path, message: str) -> None:
+ """Increment the counter for failed reformatting. Write out a message."""
+ err(f"error: cannot format {src}: {message}")
+ self.failure_count += 1
+
+ def path_ignored(self, path: Path, message: str) -> None:
+ if self.verbose:
+ out(f"{path} ignored: {message}", bold=False)
+
+ @property
+ def return_code(self) -> int:
+ """Return the exit code that the app should use.
+
+ This considers the current state of changed files and failures:
+ - if there were any failures, return 123;
+ - if any files were changed and --check is being used, return 1;
+ - otherwise return 0.
+ """
+ # According to http://tldp.org/LDP/abs/html/exitcodes.html starting with
+ # 126 we have special return codes reserved by the shell.
+ if self.failure_count:
+ return 123
+
+ elif self.change_count and self.check:
+ return 1
+
+ return 0
+
+ def __str__(self) -> str:
+ """Render a color report of the current state.
+
+ Use `click.unstyle` to remove colors.
+ """
+ if self.check:
+ reformatted = "would be reformatted"
+ unchanged = "would be left unchanged"
+ failed = "would fail to reformat"
+ else:
+ reformatted = "reformatted"
+ unchanged = "left unchanged"
+ failed = "failed to reformat"
+ report = []
+ if self.change_count:
+ s = "s" if self.change_count > 1 else ""
+ report.append(
+ click.style(f"{self.change_count} file{s} {reformatted}", bold=True)
+ )
+ if self.same_count:
+ s = "s" if self.same_count > 1 else ""
+ report.append(f"{self.same_count} file{s} {unchanged}")
+ if self.failure_count:
+ s = "s" if self.failure_count > 1 else ""
+ report.append(
+ click.style(f"{self.failure_count} file{s} {failed}", fg="red")
+ )
+ return ", ".join(report) + "."
+
+
+def parse_ast(src: str) -> Union[ast.AST, ast3.AST, ast27.AST]:
+ filename = "<unknown>"
+ if sys.version_info >= (3, 8):
+ # TODO: support Python 4+ ;)
+ for minor_version in range(sys.version_info[1], 4, -1):
+ try:
+ return ast.parse(src, filename, feature_version=(3, minor_version))
+ except SyntaxError:
+ continue
+ else:
+ for feature_version in (7, 6):
+ try:
+ return ast3.parse(src, filename, feature_version=feature_version)
+ except SyntaxError:
+ continue
+
+ return ast27.parse(src)
+
+
+def _fixup_ast_constants(
+ node: Union[ast.AST, ast3.AST, ast27.AST]
+) -> Union[ast.AST, ast3.AST, ast27.AST]:
+ """Map ast nodes deprecated in 3.8 to Constant."""
+ # casts are required until this is released:
+ # https://github.com/python/typeshed/pull/3142
+ if isinstance(node, (ast.Str, ast3.Str, ast27.Str, ast.Bytes, ast3.Bytes)):
+ return cast(ast.AST, ast.Constant(value=node.s))
+ elif isinstance(node, (ast.Num, ast3.Num, ast27.Num)):
+ return cast(ast.AST, ast.Constant(value=node.n))
+ elif isinstance(node, (ast.NameConstant, ast3.NameConstant)):
+ return cast(ast.AST, ast.Constant(value=node.value))
+ return node
+
+
+def assert_equivalent(src: str, dst: str) -> None:
+ """Raise AssertionError if `src` and `dst` aren't equivalent."""
+
+ def _v(node: Union[ast.AST, ast3.AST, ast27.AST], depth: int = 0) -> Iterator[str]:
+ """Simple visitor generating strings to compare ASTs by content."""
+
+ node = _fixup_ast_constants(node)
+
+ yield f"{' ' * depth}{node.__class__.__name__}("
+
+ for field in sorted(node._fields):
+ # TypeIgnore has only one field 'lineno' which breaks this comparison
+ type_ignore_classes = (ast3.TypeIgnore, ast27.TypeIgnore)
+ if sys.version_info >= (3, 8):
+ type_ignore_classes += (ast.TypeIgnore,)
+ if isinstance(node, type_ignore_classes):
+ break
+
+ try:
+ value = getattr(node, field)
+ except AttributeError:
+ continue
+
+ yield f"{' ' * (depth+1)}{field}="
+
+ if isinstance(value, list):
+ for item in value:
+ # Ignore nested tuples within del statements, because we may insert
+ # parentheses and they change the AST.
+ if (
+ field == "targets"
+ and isinstance(node, (ast.Delete, ast3.Delete, ast27.Delete))
+ and isinstance(item, (ast.Tuple, ast3.Tuple, ast27.Tuple))
+ ):
+ for item in item.elts:
+ yield from _v(item, depth + 2)
+ elif isinstance(item, (ast.AST, ast3.AST, ast27.AST)):
+ yield from _v(item, depth + 2)
+
+ elif isinstance(value, (ast.AST, ast3.AST, ast27.AST)):
+ yield from _v(value, depth + 2)
+
+ else:
+ yield f"{' ' * (depth+2)}{value!r}, # {value.__class__.__name__}"
+
+ yield f"{' ' * depth}) # /{node.__class__.__name__}"
+
+ try:
+ src_ast = parse_ast(src)
+ except Exception as exc:
+ raise AssertionError(
+ f"cannot use --safe with this file; failed to parse source file. "
+ f"AST error message: {exc}"
+ )
+
+ try:
+ dst_ast = parse_ast(dst)
+ except Exception as exc:
+ log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst)
+ raise AssertionError(
+ f"INTERNAL ERROR: Black produced invalid code: {exc}. "
+ f"Please report a bug on https://github.com/psf/black/issues. "
+ f"This invalid output might be helpful: {log}"
+ ) from None
+
+ src_ast_str = "\n".join(_v(src_ast))
+ dst_ast_str = "\n".join(_v(dst_ast))
+ if src_ast_str != dst_ast_str:
+ log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
+ raise AssertionError(
+ f"INTERNAL ERROR: Black produced code that is not equivalent to "
+ f"the source. "
+ f"Please report a bug on https://github.com/psf/black/issues. "
+ f"This diff might be helpful: {log}"
+ ) from None
+
+
+def assert_stable(src: str, dst: str, mode: FileMode) -> None:
+ """Raise AssertionError if `dst` reformats differently the second time."""
+ newdst = format_str(dst, mode=mode)
+ if dst != newdst:
+ log = dump_to_file(
+ diff(src, dst, "source", "first pass"),
+ diff(dst, newdst, "first pass", "second pass"),
+ )
+ raise AssertionError(
+ f"INTERNAL ERROR: Black produced different code on the second pass "
+ f"of the formatter. "
+ f"Please report a bug on https://github.com/psf/black/issues. "
+ f"This diff might be helpful: {log}"
+ ) from None
+
+
+def dump_to_file(*output: str) -> str:
+ """Dump `output` to a temporary file. Return path to the file."""
+ with tempfile.NamedTemporaryFile(
+ mode="w", prefix="blk_", suffix=".log", delete=False, encoding="utf8"
+ ) as f:
+ for lines in output:
+ f.write(lines)
+ if lines and lines[-1] != "\n":
+ f.write("\n")
+ return f.name
+
+
+@contextmanager
+def nullcontext() -> Iterator[None]:
+ """Return context manager that does nothing.
+ Similar to `nullcontext` from python 3.7"""
+ yield
+
+
+def diff(a: str, b: str, a_name: str, b_name: str) -> str:
+ """Return a unified diff string between strings `a` and `b`."""
+ import difflib
+
+ a_lines = [line + "\n" for line in a.split("\n")]
+ b_lines = [line + "\n" for line in b.split("\n")]
+ return "".join(
+ difflib.unified_diff(a_lines, b_lines, fromfile=a_name, tofile=b_name, n=5)
+ )
+
+
+def cancel(tasks: Iterable[asyncio.Task]) -> None:
+ """asyncio signal handler that cancels all `tasks` and reports to stderr."""
+ err("Aborted!")
+ for task in tasks:
+ task.cancel()
+
+
+def shutdown(loop: asyncio.AbstractEventLoop) -> None:
+ """Cancel all pending tasks on `loop`, wait for them, and close the loop."""
+ try:
+ if sys.version_info[:2] >= (3, 7):
+ all_tasks = asyncio.all_tasks
+ else:
+ all_tasks = asyncio.Task.all_tasks
+ # This part is borrowed from asyncio/runners.py in Python 3.7b2.
+ to_cancel = [task for task in all_tasks(loop) if not task.done()]
+ if not to_cancel:
+ return
+
+ for task in to_cancel:
+ task.cancel()
+ loop.run_until_complete(
+ asyncio.gather(*to_cancel, loop=loop, return_exceptions=True)
+ )
+ finally:
+ # `concurrent.futures.Future` objects cannot be cancelled once they
+ # are already running. There might be some when the `shutdown()` happened.
+ # Silence their logger's spew about the event loop being closed.
+ cf_logger = logging.getLogger("concurrent.futures")
+ cf_logger.setLevel(logging.CRITICAL)
+ loop.close()
+
+
+def sub_twice(regex: Pattern[str], replacement: str, original: str) -> str:
+ """Replace `regex` with `replacement` twice on `original`.
+
+ This is used by string normalization to perform replaces on
+ overlapping matches.
+ """
+ return regex.sub(replacement, regex.sub(replacement, original))
+
+
+def re_compile_maybe_verbose(regex: str) -> Pattern[str]:
+ """Compile a regular expression string in `regex`.
+
+ If it contains newlines, use verbose mode.
+ """
+ if "\n" in regex:
+ regex = "(?x)" + regex
+ return re.compile(regex)
+
+
+def enumerate_reversed(sequence: Sequence[T]) -> Iterator[Tuple[Index, T]]:
+ """Like `reversed(enumerate(sequence))` if that were possible."""
+ index = len(sequence) - 1
+ for element in reversed(sequence):
+ yield (index, element)
+ index -= 1
+
+
+def enumerate_with_length(
+ line: Line, reversed: bool = False
+) -> Iterator[Tuple[Index, Leaf, int]]:
+ """Return an enumeration of leaves with their length.
+
+ Stops prematurely on multiline strings and standalone comments.
+ """
+ op = cast(
+ Callable[[Sequence[Leaf]], Iterator[Tuple[Index, Leaf]]],
+ enumerate_reversed if reversed else enumerate,
+ )
+ for index, leaf in op(line.leaves):
+ length = len(leaf.prefix) + len(leaf.value)
+ if "\n" in leaf.value:
+ return # Multiline strings, we can't continue.
+
+ for comment in line.comments_after(leaf):
+ length += len(comment.value)
+
+ yield index, leaf, length
+
+
+def is_line_short_enough(line: Line, *, line_length: int, line_str: str = "") -> bool:
+ """Return True if `line` is no longer than `line_length`.
+
+ Uses the provided `line_str` rendering, if any, otherwise computes a new one.
+ """
+ if not line_str:
+ line_str = str(line).strip("\n")
+ return (
+ len(line_str) <= line_length
+ and "\n" not in line_str # multiline strings
+ and not line.contains_standalone_comments()
+ )
+
+
+def can_be_split(line: Line) -> bool:
+ """Return False if the line cannot be split *for sure*.
+
+ This is not an exhaustive search but a cheap heuristic that we can use to
+ avoid some unfortunate formattings (mostly around wrapping unsplittable code
+ in unnecessary parentheses).
+ """
+ leaves = line.leaves
+ if len(leaves) < 2:
+ return False
+
+ if leaves[0].type == token.STRING and leaves[1].type == token.DOT:
+ call_count = 0
+ dot_count = 0
+ next = leaves[-1]
+ for leaf in leaves[-2::-1]:
+ if leaf.type in OPENING_BRACKETS:
+ if next.type not in CLOSING_BRACKETS:
+ return False
+
+ call_count += 1
+ elif leaf.type == token.DOT:
+ dot_count += 1
+ elif leaf.type == token.NAME:
+ if not (next.type == token.DOT or next.type in OPENING_BRACKETS):
+ return False
+
+ elif leaf.type not in CLOSING_BRACKETS:
+ return False
+
+ if dot_count > 1 and call_count > 1:
+ return False
+
+ return True
+
+
+def can_omit_invisible_parens(line: Line, line_length: int) -> bool:
+ """Does `line` have a shape safe to reformat without optional parens around it?
+
+ Returns True for only a subset of potentially nice looking formattings but
+ the point is to not return false positives that end up producing lines that
+ are too long.
+ """
+ bt = line.bracket_tracker
+ if not bt.delimiters:
+ # Without delimiters the optional parentheses are useless.
+ return True
+
+ max_priority = bt.max_delimiter_priority()
+ if bt.delimiter_count_with_priority(max_priority) > 1:
+ # With more than one delimiter of a kind the optional parentheses read better.
+ return False
+
+ if max_priority == DOT_PRIORITY:
+ # A single stranded method call doesn't require optional parentheses.
+ return True
+
+ assert len(line.leaves) >= 2, "Stranded delimiter"
+
+ first = line.leaves[0]
+ second = line.leaves[1]
+ penultimate = line.leaves[-2]
+ last = line.leaves[-1]
+
+ # With a single delimiter, omit if the expression starts or ends with
+ # a bracket.
+ if first.type in OPENING_BRACKETS and second.type not in CLOSING_BRACKETS:
+ remainder = False
+ length = 4 * line.depth
+ for _index, leaf, leaf_length in enumerate_with_length(line):
+ if leaf.type in CLOSING_BRACKETS and leaf.opening_bracket is first:
+ remainder = True
+ if remainder:
+ length += leaf_length
+ if length > line_length:
+ break
+
+ if leaf.type in OPENING_BRACKETS:
+ # There are brackets we can further split on.
+ remainder = False
+
+ else:
+ # checked the entire string and line length wasn't exceeded
+ if len(line.leaves) == _index + 1:
+ return True
+
+ # Note: we are not returning False here because a line might have *both*
+ # a leading opening bracket and a trailing closing bracket. If the
+ # opening bracket doesn't match our rule, maybe the closing will.
+
+ if (
+ last.type == token.RPAR
+ or last.type == token.RBRACE
+ or (
+ # don't use indexing for omitting optional parentheses;
+ # it looks weird
+ last.type == token.RSQB
+ and last.parent
+ and last.parent.type != syms.trailer
+ )
+ ):
+ if penultimate.type in OPENING_BRACKETS:
+ # Empty brackets don't help.
+ return False
+
+ if is_multiline_string(first):
+ # Additional wrapping of a multiline string in this situation is
+ # unnecessary.
+ return True
+
+ length = 4 * line.depth
+ seen_other_brackets = False
+ for _index, leaf, leaf_length in enumerate_with_length(line):
+ length += leaf_length
+ if leaf is last.opening_bracket:
+ if seen_other_brackets or length <= line_length:
+ return True
+
+ elif leaf.type in OPENING_BRACKETS:
+ # There are brackets we can further split on.
+ seen_other_brackets = True
+
+ return False
+
+
+def get_cache_file(mode: FileMode) -> Path:
+ return CACHE_DIR / f"cache.{mode.get_cache_key()}.pickle"
+
+
+def read_cache(mode: FileMode) -> Cache:
+ """Read the cache if it exists and is well formed.
+
+ If it is not well formed, the call to write_cache later should resolve the issue.
+ """
+ cache_file = get_cache_file(mode)
+ if not cache_file.exists():
+ return {}
+
+ with cache_file.open("rb") as fobj:
+ try:
+ cache: Cache = pickle.load(fobj)
+ except pickle.UnpicklingError:
+ return {}
+
+ return cache
+
+
+def get_cache_info(path: Path) -> CacheInfo:
+ """Return the information used to check if a file is already formatted or not."""
+ stat = path.stat()
+ return stat.st_mtime, stat.st_size
+
+
+def filter_cached(cache: Cache, sources: Iterable[Path]) -> Tuple[Set[Path], Set[Path]]:
+ """Split an iterable of paths in `sources` into two sets.
+
+ The first contains paths of files that modified on disk or are not in the
+ cache. The other contains paths to non-modified files.
+ """
+ todo, done = set(), set()
+ for src in sources:
+ src = src.resolve()
+ if cache.get(src) != get_cache_info(src):
+ todo.add(src)
+ else:
+ done.add(src)
+ return todo, done
+
+
+def write_cache(cache: Cache, sources: Iterable[Path], mode: FileMode) -> None:
+ """Update the cache file."""
+ cache_file = get_cache_file(mode)
+ try:
+ CACHE_DIR.mkdir(parents=True, exist_ok=True)
+ new_cache = {**cache, **{src.resolve(): get_cache_info(src) for src in sources}}
+ with tempfile.NamedTemporaryFile(dir=str(cache_file.parent), delete=False) as f:
+ pickle.dump(new_cache, f, protocol=pickle.HIGHEST_PROTOCOL)
+ os.replace(f.name, cache_file)
+ except OSError:
+ pass
+
+
+def patch_click() -> None:
+ """Make Click not crash.
+
+ On certain misconfigured environments, Python 3 selects the ASCII encoding as the
+ default which restricts paths that it can access during the lifetime of the
+ application. Click refuses to work in this scenario by raising a RuntimeError.
+
+ In case of Black the likelihood that non-ASCII characters are going to be used in
+ file paths is minimal since it's Python source code. Moreover, this crash was
+ spurious on Python 3.7 thanks to PEP 538 and PEP 540.
+ """
+ try:
+ from click import core
+ from click import _unicodefun # type: ignore
+ except ModuleNotFoundError:
+ return
+
+ for module in (core, _unicodefun):
+ if hasattr(module, "_verify_python3_env"):
+ module._verify_python3_env = lambda: None
+
+
+def patched_main() -> None:
+ freeze_support()
+ patch_click()
+ main()
+
+
+if __name__ == "__main__":
+ patched_main()