350 lines
11 KiB
Python
350 lines
11 KiB
Python
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"""
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Code of the config system; not related to fontTools or fonts in particular.
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The options that are specific to fontTools are in :mod:`fontTools.config`.
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To create your own config system, you need to create an instance of
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:class:`Options`, and a subclass of :class:`AbstractConfig` with its
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``options`` class variable set to your instance of Options.
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"""
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from __future__ import annotations
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import logging
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from dataclasses import dataclass
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from typing import (
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Any,
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Callable,
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ClassVar,
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Dict,
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Iterable,
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Mapping,
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MutableMapping,
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Optional,
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Set,
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Union,
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)
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log = logging.getLogger(__name__)
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__all__ = [
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"AbstractConfig",
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"ConfigAlreadyRegisteredError",
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"ConfigError",
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"ConfigUnknownOptionError",
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"ConfigValueParsingError",
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"ConfigValueValidationError",
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"Option",
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"Options",
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]
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class ConfigError(Exception):
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"""Base exception for the config module."""
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class ConfigAlreadyRegisteredError(ConfigError):
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"""Raised when a module tries to register a configuration option that
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already exists.
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Should not be raised too much really, only when developing new fontTools
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modules.
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"""
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def __init__(self, name):
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super().__init__(f"Config option {name} is already registered.")
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class ConfigValueParsingError(ConfigError):
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"""Raised when a configuration value cannot be parsed."""
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def __init__(self, name, value):
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super().__init__(
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f"Config option {name}: value cannot be parsed (given {repr(value)})"
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)
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class ConfigValueValidationError(ConfigError):
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"""Raised when a configuration value cannot be validated."""
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def __init__(self, name, value):
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super().__init__(
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f"Config option {name}: value is invalid (given {repr(value)})"
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)
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class ConfigUnknownOptionError(ConfigError):
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"""Raised when a configuration option is unknown."""
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def __init__(self, option_or_name):
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name = (
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f"'{option_or_name.name}' (id={id(option_or_name)})>"
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if isinstance(option_or_name, Option)
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else f"'{option_or_name}'"
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)
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super().__init__(f"Config option {name} is unknown")
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# eq=False because Options are unique, not fungible objects
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@dataclass(frozen=True, eq=False)
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class Option:
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name: str
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"""Unique name identifying the option (e.g. package.module:MY_OPTION)."""
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help: str
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"""Help text for this option."""
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default: Any
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"""Default value for this option."""
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parse: Callable[[str], Any]
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"""Turn input (e.g. string) into proper type. Only when reading from file."""
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validate: Optional[Callable[[Any], bool]] = None
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"""Return true if the given value is an acceptable value."""
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@staticmethod
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def parse_optional_bool(v: str) -> Optional[bool]:
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s = str(v).lower()
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if s in {"0", "no", "false"}:
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return False
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if s in {"1", "yes", "true"}:
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return True
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if s in {"auto", "none"}:
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return None
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raise ValueError("invalid optional bool: {v!r}")
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@staticmethod
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def validate_optional_bool(v: Any) -> bool:
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return v is None or isinstance(v, bool)
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class Options(Mapping):
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"""Registry of available options for a given config system.
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Define new options using the :meth:`register()` method.
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Access existing options using the Mapping interface.
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"""
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__options: Dict[str, Option]
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def __init__(self, other: "Options" = None) -> None:
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self.__options = {}
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if other is not None:
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for option in other.values():
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self.register_option(option)
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def register(
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self,
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name: str,
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help: str,
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default: Any,
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parse: Callable[[str], Any],
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validate: Optional[Callable[[Any], bool]] = None,
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) -> Option:
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"""Create and register a new option."""
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return self.register_option(Option(name, help, default, parse, validate))
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def register_option(self, option: Option) -> Option:
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"""Register a new option."""
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name = option.name
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if name in self.__options:
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raise ConfigAlreadyRegisteredError(name)
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self.__options[name] = option
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return option
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def is_registered(self, option: Option) -> bool:
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"""Return True if the same option object is already registered."""
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return self.__options.get(option.name) is option
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def __getitem__(self, key: str) -> Option:
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return self.__options.__getitem__(key)
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def __iter__(self) -> Iterator[str]:
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return self.__options.__iter__()
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def __len__(self) -> int:
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return self.__options.__len__()
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def __repr__(self) -> str:
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return (
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f"{self.__class__.__name__}({{\n"
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+ "".join(
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f" {k!r}: Option(default={v.default!r}, ...),\n"
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for k, v in self.__options.items()
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)
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+ "})"
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)
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_USE_GLOBAL_DEFAULT = object()
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class AbstractConfig(MutableMapping):
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"""
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Create a set of config values, optionally pre-filled with values from
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the given dictionary or pre-existing config object.
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The class implements the MutableMapping protocol keyed by option name (`str`).
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For convenience its methods accept either Option or str as the key parameter.
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.. seealso:: :meth:`set()`
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This config class is abstract because it needs its ``options`` class
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var to be set to an instance of :class:`Options` before it can be
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instanciated and used.
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.. code:: python
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class MyConfig(AbstractConfig):
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options = Options()
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MyConfig.register_option( "test:option_name", "This is an option", 0, int, lambda v: isinstance(v, int))
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cfg = MyConfig({"test:option_name": 10})
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"""
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options: ClassVar[Options]
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@classmethod
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def register_option(
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cls,
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name: str,
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help: str,
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default: Any,
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parse: Callable[[str], Any],
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validate: Optional[Callable[[Any], bool]] = None,
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) -> Option:
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"""Register an available option in this config system."""
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return cls.options.register(
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name, help=help, default=default, parse=parse, validate=validate
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)
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_values: Dict[str, Any]
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def __init__(
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self,
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values: Union[AbstractConfig, Dict[Union[Option, str], Any]] = {},
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parse_values: bool = False,
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skip_unknown: bool = False,
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):
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self._values = {}
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values_dict = values._values if isinstance(values, AbstractConfig) else values
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for name, value in values_dict.items():
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self.set(name, value, parse_values, skip_unknown)
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def _resolve_option(self, option_or_name: Union[Option, str]) -> Option:
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if isinstance(option_or_name, Option):
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option = option_or_name
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if not self.options.is_registered(option):
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raise ConfigUnknownOptionError(option)
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return option
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elif isinstance(option_or_name, str):
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name = option_or_name
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try:
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return self.options[name]
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except KeyError:
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raise ConfigUnknownOptionError(name)
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else:
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raise TypeError(
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"expected Option or str, found "
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f"{type(option_or_name).__name__}: {option_or_name!r}"
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)
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def set(
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self,
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option_or_name: Union[Option, str],
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value: Any,
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parse_values: bool = False,
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skip_unknown: bool = False,
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):
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"""Set the value of an option.
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Args:
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* `option_or_name`: an `Option` object or its name (`str`).
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* `value`: the value to be assigned to given option.
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* `parse_values`: parse the configuration value from a string into
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its proper type, as per its `Option` object. The default
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behavior is to raise `ConfigValueValidationError` when the value
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is not of the right type. Useful when reading options from a
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file type that doesn't support as many types as Python.
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* `skip_unknown`: skip unknown configuration options. The default
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behaviour is to raise `ConfigUnknownOptionError`. Useful when
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reading options from a configuration file that has extra entries
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(e.g. for a later version of fontTools)
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"""
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try:
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option = self._resolve_option(option_or_name)
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except ConfigUnknownOptionError as e:
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if skip_unknown:
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log.debug(str(e))
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return
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raise
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# Can be useful if the values come from a source that doesn't have
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# strict typing (.ini file? Terminal input?)
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if parse_values:
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try:
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value = option.parse(value)
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except Exception as e:
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raise ConfigValueParsingError(option.name, value) from e
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if option.validate is not None and not option.validate(value):
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raise ConfigValueValidationError(option.name, value)
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self._values[option.name] = value
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def get(
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self, option_or_name: Union[Option, str], default: Any = _USE_GLOBAL_DEFAULT
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) -> Any:
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"""
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Get the value of an option. The value which is returned is the first
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provided among:
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1. a user-provided value in the options's ``self._values`` dict
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2. a caller-provided default value to this method call
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3. the global default for the option provided in ``fontTools.config``
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This is to provide the ability to migrate progressively from config
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options passed as arguments to fontTools APIs to config options read
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from the current TTFont, e.g.
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.. code:: python
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def fontToolsAPI(font, some_option):
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value = font.cfg.get("someLib.module:SOME_OPTION", some_option)
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# use value
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That way, the function will work the same for users of the API that
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still pass the option to the function call, but will favour the new
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config mechanism if the given font specifies a value for that option.
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"""
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option = self._resolve_option(option_or_name)
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if option.name in self._values:
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return self._values[option.name]
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if default is not _USE_GLOBAL_DEFAULT:
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return default
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return option.default
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def copy(self):
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return self.__class__(self._values)
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def __getitem__(self, option_or_name: Union[Option, str]) -> Any:
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return self.get(option_or_name)
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def __setitem__(self, option_or_name: Union[Option, str], value: Any) -> None:
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return self.set(option_or_name, value)
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def __delitem__(self, option_or_name: Union[Option, str]) -> None:
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option = self._resolve_option(option_or_name)
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del self._values[option.name]
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def __iter__(self) -> Iterable[str]:
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return self._values.__iter__()
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def __len__(self) -> int:
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return len(self._values)
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def __repr__(self) -> str:
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return f"{self.__class__.__name__}({repr(self._values)})"
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