tests/test-config-env.py

rust: iterator bindings to C code

In this changeset, still made of Rust code only,
we expose the Rust iterator for instantiation and
consumption from C code.

The idea is that both the index and index_get_parents()
will be passed from the C extension, hence avoiding a hard
link dependency to parsers.so, so that the crate can
still be built and tested independently.

On the other hand, parsers.so will use the symbols
defined in this changeset.

# Test the config layer generated by environment variables

from __future__ import absolute_import, print_function

import os

from mercurial import (
    encoding,
    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')]

rcutil.systemrcpath = systemrcpath
rcutil.userrcpath = userrcpath
os.path.isdir = lambda x: False # hack: do not load default.d/*.rc

# 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'})