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authorDaniel Baumann <daniel.baumann@progress-linux.org>2020-03-24 21:59:15 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2020-03-24 21:59:15 +0000
commit63fad53303381388673073de580a32088a4ef0fe (patch)
treea2c5c329ee5e79a220fac7e079283235fecc0cda /pre_commit/envcontext.py
parentInitial commit. (diff)
downloadpre-commit-63fad53303381388673073de580a32088a4ef0fe.tar.xz
pre-commit-63fad53303381388673073de580a32088a4ef0fe.zip
Adding upstream version 2.2.0.upstream/2.2.0
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'pre_commit/envcontext.py')
-rw-r--r--pre_commit/envcontext.py67
1 files changed, 67 insertions, 0 deletions
diff --git a/pre_commit/envcontext.py b/pre_commit/envcontext.py
new file mode 100644
index 0000000..16d3d15
--- /dev/null
+++ b/pre_commit/envcontext.py
@@ -0,0 +1,67 @@
+import contextlib
+import enum
+import os
+from typing import Generator
+from typing import NamedTuple
+from typing import Optional
+from typing import Tuple
+from typing import Union
+
+from pre_commit.util import EnvironT
+
+
+class _Unset(enum.Enum):
+ UNSET = 1
+
+
+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: EnvironT) -> 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[EnvironT] = 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 = 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)