mercurial/typelib.py

typing: lock in new pytype gains from making revlog related classes typeable

These were pretty clean changes in the pyi files from earlier in this series, so
add them to the code to make it more understandable.

There's one more trivial hint that can be added to the return of
`mercurial.revlogutils.rewrite._filelog_from_filename()`, however it needs to be
imported from '..' under the conditional of `typing.TYPE_CHECKING`, and that
seems to confuse the import checker- possibly because there's already an import
block from that level.  (I would have expected a message about multiple import
statements in this case, but got one about higher level imports should come
first, no matter where I put the import statement.)

# typelib.py - type hint aliases and support
#
# Copyright 2022 Matt Harbison <[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.

import typing

from typing import (
    Callable,
)

# Note: this is slightly different from pycompat.TYPE_CHECKING, as using
# pycompat causes the BinaryIO_Proxy type to be resolved to ``object`` when
# used as the base class during a pytype run.
TYPE_CHECKING = typing.TYPE_CHECKING


# The BinaryIO class provides empty methods, which at runtime means that
# ``__getattr__`` on the proxy classes won't get called for the methods that
# should delegate to the internal object.  So to avoid runtime changes because
# of the required typing inheritance, just use BinaryIO when typechecking, and
# ``object`` otherwise.
if TYPE_CHECKING:
    from typing import (
        BinaryIO,
        Union,
    )

    from . import (
        node,
        posix,
        windows,
    )

    BinaryIO_Proxy = BinaryIO
    CacheStat = Union[posix.cachestat, windows.cachestat]
    NodeConstants = node.sha1nodeconstants
else:
    from typing import Any

    BinaryIO_Proxy = object
    CacheStat = Any
    NodeConstants = Any

# scmutil.getuipathfn() related callback.
UiPathFn = Callable[[bytes], bytes]