view contrib/byteify-strings.py @ 46527:018d622e814d

test-copies: reinstall initial identical (empty) files for chained copied

This effectively back out changeset deeb215be337. Changeset deeb215be33 does not
really include a justification for its change and make mes uncomfortable. I have
been thinking about it and they are two options:

- either having empty/full files does not make a difference, and deeb215be337 is
  a gratuitous changes.

- either having empty/full files do make a difference and deeb215be33 silently
  change the test coverage. In such situation if we want the "not empty" case to
  be tested, we should add new cases to cover them

In practice, we know that the "file content did not change, but merge still need
to create a new filenode" case exists (for example if merging result in similar
content but both parent of the file need to be recorded), and that such case are
easy to miss/mess-up in the tests. Having all the file using the same (empty)
content was done on purpose to increase the coverage of such corner case.

As a result I am reinstalling the previous test situation. To
increase the coverage of some case involving content-merge in
test-copies-chain-merge.t, we will add a new, dedicated, cases later in this
series, once various cleanup and test improvement have been set in place.

This changeset starts with reinstalling the previous situation as (1) it is more
fragile, so I am more confided getting it back in the initial situation, (2) I
have specific test further down the line that are base on these one.

The next changeset will slightly alter the test to use non-empty files for these
tests (with identical content). It should help to make the initial intent "merge file with identical
content" clearer. I am still using a two steps (backout, then change content)
approach to facilitate careful validation of the output change.

Doing so has a large impact on the output of the "copy info in changeset extra" variant
added in 5e72827dae1e (2 changesets after deeb215be33). It seems to highlight
various breakage when merge without content change are involved, this is a good
example of why we want to explicitly test theses cases. Because the different
-do- matters a lot.

Fixing the "copy info in changeset extra" is not a priority here. Because (1)
this changeset does not break anything, it only highlight that they were always
broken. (2) the only people using "copy info in changeset extra" do not have
merge.

Differential Revision: https://phab.mercurial-scm.org/D9587

#!/usr/bin/env python3
#
# byteify-strings.py - transform string literals to be Python 3 safe
#
# Copyright 2015 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import, print_function

import argparse
import contextlib
import errno
import os
import sys
import tempfile
import token
import tokenize


def adjusttokenpos(t, ofs):
    """Adjust start/end column of the given token"""
    return t._replace(
        start=(t.start[0], t.start[1] + ofs), end=(t.end[0], t.end[1] + ofs)
    )


def replacetokens(tokens, opts):
    """Transform a stream of tokens from raw to Python 3.

    Returns a generator of possibly rewritten tokens.

    The input token list may be mutated as part of processing. However,
    its changes do not necessarily match the output token stream.
    """
    sysstrtokens = set()

    # The following utility functions access the tokens list and i index of
    # the for i, t enumerate(tokens) loop below
    def _isop(j, *o):
        """Assert that tokens[j] is an OP with one of the given values"""
        try:
            return tokens[j].type == token.OP and tokens[j].string in o
        except IndexError:
            return False

    def _findargnofcall(n):
        """Find arg n of a call expression (start at 0)

        Returns index of the first token of that argument, or None if
        there is not that many arguments.

        Assumes that token[i + 1] is '('.

        """
        nested = 0
        for j in range(i + 2, len(tokens)):
            if _isop(j, ')', ']', '}'):
                # end of call, tuple, subscription or dict / set
                nested -= 1
                if nested < 0:
                    return None
            elif n == 0:
                # this is the starting position of arg
                return j
            elif _isop(j, '(', '[', '{'):
                nested += 1
            elif _isop(j, ',') and nested == 0:
                n -= 1

        return None

    def _ensuresysstr(j):
        """Make sure the token at j is a system string

        Remember the given token so the string transformer won't add
        the byte prefix.

        Ignores tokens that are not strings. Assumes bounds checking has
        already been done.

        """
        k = j
        currtoken = tokens[k]
        while currtoken.type in (token.STRING, token.NEWLINE, tokenize.NL):
            k += 1
            if currtoken.type == token.STRING and currtoken.string.startswith(
                ("'", '"')
            ):
                sysstrtokens.add(currtoken)
            try:
                currtoken = tokens[k]
            except IndexError:
                break

    def _isitemaccess(j):
        """Assert the next tokens form an item access on `tokens[j]` and that
        `tokens[j]` is a name.
        """
        try:
            return (
                tokens[j].type == token.NAME
                and _isop(j + 1, '[')
                and tokens[j + 2].type == token.STRING
                and _isop(j + 3, ']')
            )
        except IndexError:
            return False

    def _ismethodcall(j, *methodnames):
        """Assert the next tokens form a call to `methodname` with a string
        as first argument on `tokens[j]` and that `tokens[j]` is a name.
        """
        try:
            return (
                tokens[j].type == token.NAME
                and _isop(j + 1, '.')
                and tokens[j + 2].type == token.NAME
                and tokens[j + 2].string in methodnames
                and _isop(j + 3, '(')
                and tokens[j + 4].type == token.STRING
            )
        except IndexError:
            return False

    coldelta = 0  # column increment for new opening parens
    coloffset = -1  # column offset for the current line (-1: TBD)
    parens = [(0, 0, 0, -1)]  # stack of (line, end-column, column-offset, type)
    ignorenextline = False  # don't transform the next line
    insideignoreblock = False  # don't transform until turned off
    for i, t in enumerate(tokens):
        # Compute the column offset for the current line, such that
        # the current line will be aligned to the last opening paren
        # as before.
        if coloffset < 0:
            lastparen = parens[-1]
            if t.start[1] == lastparen[1]:
                coloffset = lastparen[2]
            elif t.start[1] + 1 == lastparen[1] and lastparen[3] not in (
                token.NEWLINE,
                tokenize.NL,
            ):
                # fix misaligned indent of s/util.Abort/error.Abort/
                coloffset = lastparen[2] + (lastparen[1] - t.start[1])
            else:
                coloffset = 0

        # Reset per-line attributes at EOL.
        if t.type in (token.NEWLINE, tokenize.NL):
            yield adjusttokenpos(t, coloffset)
            coldelta = 0
            coloffset = -1
            if not insideignoreblock:
                ignorenextline = (
                    tokens[i - 1].type == token.COMMENT
                    and tokens[i - 1].string == "# no-py3-transform"
                )
            continue

        if t.type == token.COMMENT:
            if t.string == "# py3-transform: off":
                insideignoreblock = True
            if t.string == "# py3-transform: on":
                insideignoreblock = False

        if ignorenextline or insideignoreblock:
            yield adjusttokenpos(t, coloffset)
            continue

        # Remember the last paren position.
        if _isop(i, '(', '[', '{'):
            parens.append(t.end + (coloffset + coldelta, tokens[i + 1].type))
        elif _isop(i, ')', ']', '}'):
            parens.pop()

        # Convert most string literals to byte literals. String literals
        # in Python 2 are bytes. String literals in Python 3 are unicode.
        # Most strings in Mercurial are bytes and unicode strings are rare.
        # Rather than rewrite all string literals to use ``b''`` to indicate
        # byte strings, we apply this token transformer to insert the ``b``
        # prefix nearly everywhere.
        if t.type == token.STRING and t not in sysstrtokens:
            s = t.string

            # Preserve docstrings as string literals. This is inconsistent
            # with regular unprefixed strings. However, the
            # "from __future__" parsing (which allows a module docstring to
            # exist before it) doesn't properly handle the docstring if it
            # is b''' prefixed, leading to a SyntaxError. We leave all
            # docstrings as unprefixed to avoid this. This means Mercurial
            # components touching docstrings need to handle unicode,
            # unfortunately.
            if s[0:3] in ("'''", '"""'):
                # If it's assigned to something, it's not a docstring
                if not _isop(i - 1, '='):
                    yield adjusttokenpos(t, coloffset)
                    continue

            # If the first character isn't a quote, it is likely a string
            # prefixing character (such as 'b', 'u', or 'r'. Ignore.
            if s[0] not in ("'", '"'):
                yield adjusttokenpos(t, coloffset)
                continue

            # String literal. Prefix to make a b'' string.
            yield adjusttokenpos(t._replace(string='b%s' % t.string), coloffset)
            coldelta += 1
            continue

        # This looks like a function call.
        if t.type == token.NAME and _isop(i + 1, '('):
            fn = t.string

            # *attr() builtins don't accept byte strings to 2nd argument.
            if (
                fn
                in (
                    'getattr',
                    'setattr',
                    'hasattr',
                    'safehasattr',
                    'wrapfunction',
                    'wrapclass',
                    'addattr',
                )
                and (opts['allow-attr-methods'] or not _isop(i - 1, '.'))
            ):
                arg1idx = _findargnofcall(1)
                if arg1idx is not None:
                    _ensuresysstr(arg1idx)

            # .encode() and .decode() on str/bytes/unicode don't accept
            # byte strings on Python 3.
            elif fn in ('encode', 'decode') and _isop(i - 1, '.'):
                for argn in range(2):
                    argidx = _findargnofcall(argn)
                    if argidx is not None:
                        _ensuresysstr(argidx)

            # It changes iteritems/values to items/values as they are not
            # present in Python 3 world.
            elif opts['dictiter'] and fn in ('iteritems', 'itervalues'):
                yield adjusttokenpos(t._replace(string=fn[4:]), coloffset)
                continue

        if t.type == token.NAME and t.string in opts['treat-as-kwargs']:
            if _isitemaccess(i):
                _ensuresysstr(i + 2)
            if _ismethodcall(i, 'get', 'pop', 'setdefault', 'popitem'):
                _ensuresysstr(i + 4)

        # Looks like "if __name__ == '__main__'".
        if (
            t.type == token.NAME
            and t.string == '__name__'
            and _isop(i + 1, '==')
        ):
            _ensuresysstr(i + 2)

        # Emit unmodified token.
        yield adjusttokenpos(t, coloffset)


def process(fin, fout, opts):
    tokens = tokenize.tokenize(fin.readline)
    tokens = replacetokens(list(tokens), opts)
    fout.write(tokenize.untokenize(tokens))


def tryunlink(fname):
    try:
        os.unlink(fname)
    except OSError as err:
        if err.errno != errno.ENOENT:
            raise


@contextlib.contextmanager
def editinplace(fname):
    n = os.path.basename(fname)
    d = os.path.dirname(fname)
    fp = tempfile.NamedTemporaryFile(
        prefix='.%s-' % n, suffix='~', dir=d, delete=False
    )
    try:
        yield fp
        fp.close()
        if os.name == 'nt':
            tryunlink(fname)
        os.rename(fp.name, fname)
    finally:
        fp.close()
        tryunlink(fp.name)


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument(
        '--version', action='version', version='Byteify strings 1.0'
    )
    ap.add_argument(
        '-i',
        '--inplace',
        action='store_true',
        default=False,
        help='edit files in place',
    )
    ap.add_argument(
        '--dictiter',
        action='store_true',
        default=False,
        help='rewrite iteritems() and itervalues()',
    ),
    ap.add_argument(
        '--allow-attr-methods',
        action='store_true',
        default=False,
        help='also handle attr*() when they are methods',
    ),
    ap.add_argument(
        '--treat-as-kwargs',
        nargs="+",
        default=[],
        help="ignore kwargs-like objects",
    ),
    ap.add_argument('files', metavar='FILE', nargs='+', help='source file')
    args = ap.parse_args()
    opts = {
        'dictiter': args.dictiter,
        'treat-as-kwargs': set(args.treat_as_kwargs),
        'allow-attr-methods': args.allow_attr_methods,
    }
    for fname in args.files:
        fname = os.path.realpath(fname)
        if args.inplace:
            with editinplace(fname) as fout:
                with open(fname, 'rb') as fin:
                    process(fin, fout, opts)
        else:
            with open(fname, 'rb') as fin:
                fout = sys.stdout.buffer
                process(fin, fout, opts)


if __name__ == '__main__':
    if sys.version_info[0:2] < (3, 7):
        print('This script must be run under Python 3.7+')
        sys.exit(3)
    main()