view mercurial/py3kcompat.py @ 25708:d3d32643c060

wireproto: correctly escape batched args and responses (issue4739)

This issue appears to be as old as wireproto batching itself: I can
reproduce the failure as far back as 08ef6b5f3715 trivially by
rebasing the test changes in this patch, which was back in the 1.9
era. I didn't test before that change, because prior to that the
testfile has a different name and I'm lazy.

Note that the test thought it was checking this case, but it actually
wasn't: it put a literal ; in the arg and response for its greet
command, but the mangle/unmangle step defined in the test meant that
instead of "Fo, =;o" going over the wire, "Gp-!><p" went instead,
which doesn't contain any special characters (those being [.=;]) and
thus not exercising the escaping. The test has been updated to use
pre-unmangled special characters, so the request is now "Fo+<:o",
which mangles to "Gp,=;p". I have confirmed that the test fails
without the adjustment to the escaping rules in wireproto.py.

No existing clients of RPC batching were depending on the old behavior
in any way. The only *actual* users of batchable RPCs in core were:

1) largefiles, wherein it batches up many statlfile calls. It sends
hexlified hashes over the wire and gets a 0, 1, or 2 back as a
response. No risk of special characters.

2) setdiscovery, which was using heads() and known(), both of which
communicate via hexlified nodes. Again, no risk of special characters.

Since the escaping functionality has been completely broken since it
was introduced, we know that it has no users. As such, we can change
the escaping mechanism without having to worry about backwards
compatibility issues.

For the curious, this was detected by chance: it happens that the
lz4-compressed text of a test file for remotefilelog compressed to
something containing a ;, which then caused the failure when I moved
remotefilelog to using batching for file content fetching.

# py3kcompat.py - compatibility definitions for running hg in py3k
#
# Copyright 2010 Renato Cunha <[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 builtins

from numbers import Number

def bytesformatter(format, args):
    '''Custom implementation of a formatter for bytestrings.

    This function currently relies on the string formatter to do the
    formatting and always returns bytes objects.

    >>> bytesformatter(20, 10)
    0
    >>> bytesformatter('unicode %s, %s!', ('string', 'foo'))
    b'unicode string, foo!'
    >>> bytesformatter(b'test %s', 'me')
    b'test me'
    >>> bytesformatter('test %s', 'me')
    b'test me'
    >>> bytesformatter(b'test %s', b'me')
    b'test me'
    >>> bytesformatter('test %s', b'me')
    b'test me'
    >>> bytesformatter('test %d: %s', (1, b'result'))
    b'test 1: result'
    '''
    # The current implementation just converts from bytes to unicode, do
    # what's needed and then convert the results back to bytes.
    # Another alternative is to use the Python C API implementation.
    if isinstance(format, Number):
        # If the fixer erroneously passes a number remainder operation to
        # bytesformatter, we just return the correct operation
        return format % args
    if isinstance(format, bytes):
        format = format.decode('utf-8', 'surrogateescape')
    if isinstance(args, bytes):
        args = args.decode('utf-8', 'surrogateescape')
    if isinstance(args, tuple):
        newargs = []
        for arg in args:
            if isinstance(arg, bytes):
                arg = arg.decode('utf-8', 'surrogateescape')
            newargs.append(arg)
        args = tuple(newargs)
    ret = format % args
    return ret.encode('utf-8', 'surrogateescape')
builtins.bytesformatter = bytesformatter

origord = builtins.ord
def fakeord(char):
    if isinstance(char, int):
        return char
    return origord(char)
builtins.ord = fakeord

if __name__ == '__main__':
    import doctest
    doctest.testmod()