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129 lines
3.5 KiB
129 lines
3.5 KiB
import configparser
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import dataclasses
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from dataclasses import dataclass
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from pathlib import Path
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from typing import Callable
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from typing import ClassVar
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from typing import Optional
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from typing import Union
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from .helpers import make_path
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class ConfigError(BaseException):
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pass
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class MissingConfig(ConfigError):
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pass
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class MissingConfigSection(ConfigError):
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pass
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class MissingConfigItem(ConfigError):
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pass
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class ConfigValueTypeError(ConfigError):
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pass
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class _GetterDispatch:
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def __init__(self, initialdata, default_getter: Callable):
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self.default_getter = default_getter
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self.data = initialdata
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def get_fn_for_type(self, type_):
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return self.data.get(type_, self.default_getter)
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def get_typed_value(self, type_, name):
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get_fn = self.get_fn_for_type(type_)
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return get_fn(name)
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def _parse_cfg_file(filespec: Union[Path, str]):
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cfg = configparser.ConfigParser()
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try:
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filepath = make_path(filespec, check_exists=True)
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except FileNotFoundError as e:
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raise MissingConfig(f"No config file found at {filespec}") from e
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else:
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with open(filepath, encoding="utf-8") as f:
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cfg.read_file(f)
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return cfg
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def _build_getter(cfg_obj, cfg_section, method, converter=None):
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def caller(option, **kwargs):
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try:
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rv = getattr(cfg_obj, method)(cfg_section, option, **kwargs)
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except configparser.NoSectionError as nse:
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raise MissingConfigSection(
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f"No config section named {cfg_section}"
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) from nse
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except configparser.NoOptionError as noe:
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raise MissingConfigItem(f"No config item for {option}") from noe
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except ValueError as ve:
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# ConfigParser.getboolean, .getint, .getfloat raise ValueError
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# on bad types
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raise ConfigValueTypeError(
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f"Wrong value type for {option}"
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) from ve
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else:
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if converter:
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try:
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rv = converter(rv)
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except Exception as e:
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raise ConfigValueTypeError(
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f"Wrong value type for {option}"
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) from e
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return rv
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return caller
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def _build_getter_dispatch(cfg_obj, cfg_section, converters=None):
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converters = converters or {}
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default_getter = _build_getter(cfg_obj, cfg_section, "get")
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# support ConfigParser builtins
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getters = {
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int: _build_getter(cfg_obj, cfg_section, "getint"),
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bool: _build_getter(cfg_obj, cfg_section, "getboolean"),
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float: _build_getter(cfg_obj, cfg_section, "getfloat"),
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str: default_getter,
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}
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# use ConfigParser.get and convert value
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getters.update(
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{
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type_: _build_getter(
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cfg_obj, cfg_section, "get", converter=converter_fn
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)
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for type_, converter_fn in converters.items()
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}
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)
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return _GetterDispatch(getters, default_getter)
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@dataclass
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class ReadsCfg:
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section_header: ClassVar[str]
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converters: ClassVar[Optional[dict]] = None
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@classmethod
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def from_cfg_file(cls, filespec: Union[Path, str]):
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cfg = _parse_cfg_file(filespec)
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dispatch = _build_getter_dispatch(
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cfg, cls.section_header, converters=cls.converters
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)
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kwargs = {
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field.name: dispatch.get_typed_value(field.type, field.name)
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for field in dataclasses.fields(cls)
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}
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return cls(**kwargs)
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