view mercurial/interfaces/modules.py @ 51940:54d9f496f07a

interfaces: introduce and use a protocol class for the `charencoding` module

See f2832de2a46c for details when this was done for the `bdiff` module.

This lets us dump the hack where the `pure` implementation was imported during
the type checking phase to provide signatures for the module methods it
provides.  Now the protocol classes are starting to shine, because these methods
are provided by `pure.charencoding` and `cext.parsers`, and references to
`cffi.charencoding` and `cext.charencoding` are forwarded to them as appropriate
by the `policy` module.  But none of that matters, as long as the module
returned provides the listed methods.

The interface was copy/pasted from the `pure` module, but `jsonescapeu8fallback`
is omitted because it is accessed from the `pure` module directly when the
escaping fails in the primary module's `jsonescapeu8()`.

# modules.py - protocol classes for dynamically loaded modules
#
# 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 annotations

import typing

from typing import (
    Callable,
    List,
    Optional,
    Protocol,
    Tuple,
)

if typing.TYPE_CHECKING:
    BDiffBlock = Tuple[int, int, int, int]
    """An entry in the list returned by bdiff.{xdiff,}blocks()."""

    BDiffBlocksFnc = Callable[[bytes, bytes], List[BDiffBlock]]
    """The signature of `bdiff.blocks()` and `bdiff.xdiffblocks()`."""


class Base85(Protocol):
    """A Protocol class for the various base85 module implementations."""

    def b85encode(self, text: bytes, pad: bool = False) -> bytes:
        """encode text in base85 format"""

    def b85decode(self, text: bytes) -> bytes:
        """decode base85-encoded text"""


class BDiff(Protocol):
    """A Protocol class for the various bdiff module implementations."""

    def splitnewlines(self, text: bytes) -> List[bytes]:
        """like str.splitlines, but only split on newlines."""

    def bdiff(self, a: bytes, b: bytes) -> bytes:
        ...

    def blocks(self, a: bytes, b: bytes) -> List[BDiffBlock]:
        ...

    def fixws(self, text: bytes, allws: bool) -> bytes:
        ...

    xdiffblocks: Optional[BDiffBlocksFnc]
    """This method is currently only available in the ``cext`` module."""


class CharEncoding(Protocol):
    """A Protocol class for the various charencoding module implementations."""

    def isasciistr(self, s: bytes) -> bool:
        """Can the byte string be decoded with the ``ascii`` codec?"""

    def asciilower(self, s: bytes) -> bytes:
        """convert a string to lowercase if ASCII

        Raises UnicodeDecodeError if non-ASCII characters are found."""

    def asciiupper(self, s: bytes) -> bytes:
        """convert a string to uppercase if ASCII

        Raises UnicodeDecodeError if non-ASCII characters are found."""

    def jsonescapeu8fast(self, u8chars: bytes, paranoid: bool) -> bytes:
        """Convert a UTF-8 byte string to JSON-escaped form (fast path)

        Raises ValueError if non-ASCII characters have to be escaped.
        """