annotate mercurial/txnutil.py @ 51723:9367571fea21

cext: correct the argument handling of `b85encode()`

The type stub indicated that this argument is `Optional`, which implies None is
allowed.  I don't see in the documentation where that's the case for `i`[1], and
trying it in `hg debugshell` resulted in the method failing with a TypeError.  I
guess it was typed as an `int` argument because the `p` format unit wasn't added
until Python 3.3[2].

In any event, 2 clients in core (`pvec` and `obsolete`) call this with no
argument supplied, and `mdiff` calls it with True.  So I guess we've avoided the
None arg case, and when no arg is supplied, it defaults to the 0 initialization
of the `pad` variable in C.  Since the `p` format unit accepts both `int` and
None, as well as `bool`, I'm not bothering to bump the module version- this code
is more permissive than it was, in addition to being more correct.

Interestingly, when I first imported the `cext` and `pure` methods in the same
manner as the previous commit, it dropped the `Optional` part of the argument
type when generating `util.pyi`.  No idea why.

[1] https://docs.python.org/3/c-api/arg.html#numbers
[2] https://docs.python.org/3/c-api/arg.html#other-objects

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


from . import encoding


def mayhavepending(root):
    """return whether 'root' may have pending changes, which are
    visible to this process.
    """
    return root == encoding.environ.get(b'HG_PENDING')


def trypending(root, vfs, filename, **kwargs):
    """Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    """
    if mayhavepending(root):
        try:
            return (vfs(b'%s.pending' % filename, **kwargs), True)
        except FileNotFoundError:
            pass
    return (vfs(filename, **kwargs), False)