"""Contains utilities to set and retrieve dynamic variable values.
This module is a bit of a HACK, but is better than using mutable global
variables IMO.
"""
from __future__ import annotations
import codecs
from contextlib import contextmanager
import os
from pathlib import Path
import pickle
from typing import Any, Final, Iterable, Iterator, Optional, Type
from .types import ClackConfig, Config_T
_CODECS_ENCODING: Final = "base64"
_NOT_SET: Final = "CLACK_ENVVAR_NOT_SET"
[docs]
@contextmanager
def clack_envvars_set(
app_name: str,
config_types: Iterable[Type[ClackConfig]],
*,
config_file: Path = None,
cfg: ClackConfig = None,
) -> Iterator[None]:
"""Context manager that sets temporary envvars.
The following envvars are set on __enter__ and removed on __exit__:
- CLACK_APP_NAME
- CLACK_CONFIG_DEFAULTS
- CLACK_CONFIG_DICT
- CLACK_CONFIG_FILE
"""
config_defaults = {}
for some_config_type in config_types:
some_config_defaults = _config_defaults_from_config_type(
some_config_type
)
config_defaults.update(some_config_defaults)
os.environ["CLACK_APP_NAME"] = app_name
os.environ["CLACK_CONFIG_DEFAULTS"] = codecs.encode(
pickle.dumps(config_defaults), _CODECS_ENCODING
).decode()
os.environ["CLACK_CONFIG_DICT"] = (
codecs.encode(pickle.dumps(cfg.dict()), _CODECS_ENCODING).decode()
if cfg is not None
else _NOT_SET
)
os.environ["CLACK_CONFIG_FILE"] = (
_NOT_SET if config_file is None else str(config_file)
)
yield
del os.environ["CLACK_APP_NAME"]
del os.environ["CLACK_CONFIG_DEFAULTS"]
del os.environ["CLACK_CONFIG_DICT"]
del os.environ["CLACK_CONFIG_FILE"]
def _config_defaults_from_config_type(
config_type: Type[ClackConfig],
) -> dict[str, Any]:
result = {}
for key, value in config_type.__fields__.items():
if value.default is not None:
result[key] = value.default
return result
def get_app_name() -> str:
"""Getter function for CLACK_APP_NAME envvar.
Raises:
A RuntimeError if the CLACK_APP_NAME envvar is not defined.
"""
with _catch_key_error("get_app_name"):
return os.environ["CLACK_APP_NAME"]
def get_config_defaults() -> dict[str, Any]:
"""Getter function for CLACK_CONFIG_DEFAULTS envvar.
Raises:
A RuntimeError if the CLACK_CONFIG_DEFAULTS envvar is not defined.
"""
with _catch_key_error("get_config_defaults"):
config_defaults_string = os.environ["CLACK_CONFIG_DEFAULTS"]
result: dict[str, Any] = pickle.loads(
codecs.decode(config_defaults_string.encode(), _CODECS_ENCODING)
)
return result
def get_config_file() -> Optional[Path]:
"""Getter function for CLACK_CONFIG_FILE envvar.
Raises:
A RuntimeError if the CLACK_CONFIG_FILE envvar is not defined.
"""
with _catch_key_error("get_config_file"):
config_file = os.environ["CLACK_CONFIG_FILE"]
if config_file == _NOT_SET:
return None
else:
return Path(config_file)
[docs]
def get_config(cfg_type: Type[Config_T]) -> Optional[Config_T]:
"""Returns a clack configuration object of type `cfg_type`.
WARNING: This function should probably only be used when there is no way to
pass the config object directly to the calling function.
Raises:
A RuntimeError if the CLACK_CONFIG_DICT envvar is not defined.
"""
with _catch_key_error("get_config"):
clack_config_dict = os.environ["CLACK_CONFIG_DICT"]
if clack_config_dict == _NOT_SET:
return None
else:
cfg_dict = pickle.loads(
codecs.decode(clack_config_dict.encode(), _CODECS_ENCODING)
)
return cfg_type(**cfg_dict)
@contextmanager
def _catch_key_error(func_name: str) -> Iterator[None]:
try:
yield
except KeyError as e:
raise RuntimeError(
f"The {func_name}() function MUST be called INSIDE the context"
" that clack_envvars_set() creates."
) from e