view hgext/fsmonitor/pywatchman/capabilities.py @ 45095:8e04607023e5

procutil: ensure that procutil.std{out,err}.write() writes all bytes

Python 3 offers different kind of streams and it’s not guaranteed for all of
them that calling write() writes all bytes.

When Python is started in unbuffered mode, sys.std{out,err}.buffer are
instances of io.FileIO, whose write() can write less bytes for
platform-specific reasons (e.g. Linux has a 0x7ffff000 bytes maximum and could
write less if interrupted by a signal; when writing to Windows consoles, it’s
limited to 32767 bytes to avoid the "not enough space" error). This can lead to
silent loss of data, both when using sys.std{out,err}.buffer (which may in fact
not be a buffered stream) and when using the text streams sys.std{out,err}
(I’ve created a CPython bug report for that:
https://bugs.python.org/issue41221).

Python may fix the problem at some point. For now, we implement our own wrapper
for procutil.std{out,err} that calls the raw stream’s write() method until all
bytes have been written. We don’t use sys.std{out,err} for larger writes, so I
think it’s not worth the effort to patch them.

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# no unicode literals
from __future__ import absolute_import, division, print_function


def parse_version(vstr):
    res = 0
    for n in vstr.split("."):
        res = res * 1000
        res = res + int(n)
    return res


cap_versions = {
    "cmd-watch-del-all": "3.1.1",
    "cmd-watch-project": "3.1",
    "relative_root": "3.3",
    "term-dirname": "3.1",
    "term-idirname": "3.1",
    "wildmatch": "3.7",
}


def check(version, name):
    if name in cap_versions:
        return version >= parse_version(cap_versions[name])
    return False


def synthesize(vers, opts):
    """ Synthesize a capability enabled version response
        This is a very limited emulation for relatively recent feature sets
    """
    parsed_version = parse_version(vers["version"])
    vers["capabilities"] = {}
    for name in opts["optional"]:
        vers["capabilities"][name] = check(parsed_version, name)

    for name in opts["required"]:
        have = check(parsed_version, name)
        vers["capabilities"][name] = have
        if not have:
            vers["error"] = (
                "client required capability `"
                + name
                + "` is not supported by this server"
            )
    return vers