tests/test-config-env.py

worker: avoid potential partial write of pickled data

Previously, the code wrote the pickled data using os.write(). However,
os.write() can write less bytes than passed to it. To trigger the problem, the
pickled data had to be larger than 2147479552 bytes on my system.

Instead, open a file object and pass it to pickle.dump(). This also has the
advantage that it doesn’t buffer the whole pickled data in memory.

Note that the opened file must be buffered because pickle doesn’t support
unbuffered streams because unbuffered streams’ write() method might write less
bytes than passed to it (like os.write()) but pickle.dump() relies on that all
bytes are written (see https://github.com/python/cpython/issues/93050).

The side effect of using a file object and a with statement is that wfd is
explicitly closed now while it seems like before it was implicitly closed by
process exit.

# Test the config layer generated by environment variables


import os

from mercurial import (
    encoding,
    extensions,
    rcutil,
    ui as uimod,
    util,
)

from mercurial.utils import procutil

testtmp = encoding.environ[b'TESTTMP']

# prepare hgrc files
def join(name):
    return os.path.join(testtmp, name)


with open(join(b'sysrc'), 'wb') as f:
    f.write(b'[ui]\neditor=e0\n[pager]\npager=p0\n')

with open(join(b'userrc'), 'wb') as f:
    f.write(b'[ui]\neditor=e1')

# replace rcpath functions so they point to the files above
def systemrcpath():
    return [join(b'sysrc')]


def userrcpath():
    return [join(b'userrc')]


extensions.wrapfunction(rcutil, 'default_rc_resources', lambda orig: [])

rcutil.systemrcpath = systemrcpath
rcutil.userrcpath = userrcpath

# utility to print configs
def printconfigs(env):
    encoding.environ = env
    rcutil._rccomponents = None  # reset cache
    ui = uimod.ui.load()
    for section, name, value in ui.walkconfig():
        source = ui.configsource(section, name)
        procutil.stdout.write(
            b'%s.%s=%s # %s\n' % (section, name, value, util.pconvert(source))
        )
    procutil.stdout.write(b'\n')


# environment variable overrides
printconfigs({})
printconfigs({b'EDITOR': b'e2', b'PAGER': b'p2'})