pre-commit/pre_commit/envcontext.py at wip_progress_dots · pre-commit/pre-commit · GitHub

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from __future__ import absolute_import

from __future__ import unicode_literals

import collections

import contextlib

import os

UNSET = collections.namedtuple('UNSET', ())()

Var = collections.namedtuple('Var', ('name', 'default'))

Var.__new__.__defaults__ = ('',)

def format_env(parts, env):

return ''.join(

env.get(part.name, part.default) if isinstance(part, Var) else part

for part in parts

)

@contextlib.contextmanager

def envcontext(patch, _env=None):

"""In this context, `os.environ` is modified according to `patch`.

`patch` is an iterable of 2-tuples (key, value):

`key`: string

`value`:

- string: `environ[key] == value` inside the context.

- UNSET: `key not in environ` inside the context.

- template: A template is a tuple of strings and Var which will be

replaced with the previous environment

"""

env = os.environ if _env is None else _env

before = env.copy()

for k, v in patch:

if v is UNSET:

env.pop(k, None)

elif isinstance(v, tuple):

env[k] = format_env(v, before)

else:

env[k] = v

try:

yield

finally:

env.clear()

env.update(before)

pre-commit/pre_commit/envcontext.py at wip_progress_dots · pre-commit/pre-commit · GitHub

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