iframe-proxy | Sunbelt Computer Software

History

62 lines (50 loc) · 1.57 KB

Raw

import contextlib

import enum

import os

from typing import Generator

from typing import MutableMapping

from typing import NamedTuple

from typing import Optional

from typing import Tuple

from typing import Union

_Unset = enum.Enum('_Unset', 'UNSET')

UNSET = _Unset.UNSET

class Var(NamedTuple):

name: str

default: str = ''

SubstitutionT = Tuple[Union[str, Var], ...]

ValueT = Union[str, _Unset, SubstitutionT]

PatchesT = Tuple[Tuple[str, ValueT], ...]

def format_env(parts: SubstitutionT, env: MutableMapping[str, str]) -> str:

return ''.join(

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

for part in parts

)

@contextlib.contextmanager

def envcontext(

patch: PatchesT,

_env: Optional[MutableMapping[str, str]] = None,

) -> Generator[None, None, 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 = dict(env)

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)

Sunbelt Computer Software

PL/B Language Development and Support

Navigation Menu

Sunbelt Computer Software

PL/B Language Development and Support

FilesExpand file tree

envcontext.py

Latest commit

History

envcontext.py

File metadata and controls