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