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from __future__ import annotations
import os
import typing
import warnings
from pathlib import Path
class undefined:
pass
class EnvironError(Exception):
pass
class Environ(typing.MutableMapping[str, str]):
def __init__(self, environ: typing.MutableMapping[str, str] = os.environ):
self._environ = environ
self._has_been_read: set[str] = set()
def __getitem__(self, key: str) -> str:
self._has_been_read.add(key)
return self._environ.__getitem__(key)
def __setitem__(self, key: str, value: str) -> None:
if key in self._has_been_read:
raise EnvironError(f"Attempting to set environ['{key}'], but the value has already been read.")
self._environ.__setitem__(key, value)
def __delitem__(self, key: str) -> None:
if key in self._has_been_read:
raise EnvironError(f"Attempting to delete environ['{key}'], but the value has already been read.")
self._environ.__delitem__(key)
def __iter__(self) -> typing.Iterator[str]:
return iter(self._environ)
def __len__(self) -> int:
return len(self._environ)
environ = Environ()
T = typing.TypeVar("T")
class Config:
def __init__(
self,
env_file: str | Path | None = None,
environ: typing.Mapping[str, str] = environ,
env_prefix: str = "",
) -> None:
self.environ = environ
self.env_prefix = env_prefix
self.file_values: dict[str, str] = {}
if env_file is not None:
if not os.path.isfile(env_file):
warnings.warn(f"Config file '{env_file}' not found.")
else:
self.file_values = self._read_file(env_file)
@typing.overload
def __call__(self, key: str, *, default: None) -> str | None: ...
@typing.overload
def __call__(self, key: str, cast: type[T], default: T = ...) -> T: ...
@typing.overload
def __call__(self, key: str, cast: type[str] = ..., default: str = ...) -> str: ...
@typing.overload
def __call__(
self,
key: str,
cast: typing.Callable[[typing.Any], T] = ...,
default: typing.Any = ...,
) -> T: ...
@typing.overload
def __call__(self, key: str, cast: type[str] = ..., default: T = ...) -> T | str: ...
def __call__(
self,
key: str,
cast: typing.Callable[[typing.Any], typing.Any] | None = None,
default: typing.Any = undefined,
) -> typing.Any:
return self.get(key, cast, default)
def get(
self,
key: str,
cast: typing.Callable[[typing.Any], typing.Any] | None = None,
default: typing.Any = undefined,
) -> typing.Any:
key = self.env_prefix + key
if key in self.environ:
value = self.environ[key]
return self._perform_cast(key, value, cast)
if key in self.file_values:
value = self.file_values[key]
return self._perform_cast(key, value, cast)
if default is not undefined:
return self._perform_cast(key, default, cast)
raise KeyError(f"Config '{key}' is missing, and has no default.")
def _read_file(self, file_name: str | Path) -> dict[str, str]:
file_values: dict[str, str] = {}
with open(file_name) as input_file:
for line in input_file.readlines():
line = line.strip()
if "=" in line and not line.startswith("#"):
key, value = line.split("=", 1)
key = key.strip()
value = value.strip().strip("\"'")
file_values[key] = value
return file_values
def _perform_cast(
self,
key: str,
value: typing.Any,
cast: typing.Callable[[typing.Any], typing.Any] | None = None,
) -> typing.Any:
if cast is None or value is None:
return value
elif cast is bool and isinstance(value, str):
mapping = {"true": True, "1": True, "false": False, "0": False}
value = value.lower()
if value not in mapping:
raise ValueError(f"Config '{key}' has value '{value}'. Not a valid bool.")
return mapping[value]
try:
return cast(value)
except (TypeError, ValueError):
raise ValueError(f"Config '{key}' has value '{value}'. Not a valid {cast.__name__}.")
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