549 lines
20 KiB
Python
549 lines
20 KiB
Python
"""High-level introspection utilities, used to inspect type annotations."""
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from __future__ import annotations
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import sys
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import types
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from collections.abc import Generator, Sequence
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from dataclasses import InitVar
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from enum import Enum, IntEnum, auto
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from typing import Any, Literal, NamedTuple, cast
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from typing_extensions import TypeAlias, assert_never, get_args, get_origin
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from . import typing_objects
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__all__ = (
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'AnnotationSource',
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'ForbiddenQualifier',
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'InspectedAnnotation',
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'Qualifier',
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'get_literal_values',
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'inspect_annotation',
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'is_union_origin',
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)
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if sys.version_info >= (3, 10):
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def is_union_origin(obj: Any, /) -> bool:
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"""Return whether the provided origin is the union form.
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```pycon
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>>> is_union_origin(typing.Union)
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True
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>>> is_union_origin(get_origin(int | str))
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True
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```
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"""
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return typing_objects.is_union(obj) or obj is types.UnionType
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else:
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def is_union_origin(obj: Any, /) -> bool:
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"""Return whether the provided origin is the union form.
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```pycon
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>>> is_union_origin(typing.Union)
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True
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>>> is_union_origin(get_origin(int | str))
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True
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```
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"""
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return typing_objects.is_union(obj)
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def _literal_type_check(value: Any, /) -> None:
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"""Type check the provided literal value against the legal parameters."""
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if (
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not isinstance(value, (int, bytes, str, bool, Enum, typing_objects.NoneType))
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and value is not typing_objects.NoneType
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):
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raise TypeError(f'{value} is not a valid literal value, must be one of: int, bytes, str, Enum, None.')
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def get_literal_values(
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annotation: Any,
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/,
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*,
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type_check: bool = False,
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unpack_type_aliases: Literal['skip', 'lenient', 'eager'] = 'eager',
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) -> Generator[Any]:
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"""Yield the values contained in the provided [`Literal`][typing.Literal] [special form][].
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Args:
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annotation: The [`Literal`][typing.Literal] [special form][] to unpack.
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type_check: Whether to check if the literal values are [legal parameters][literal-legal-parameters].
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Raises a [`TypeError`][] otherwise.
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unpack_type_aliases: What to do when encountering [PEP 695](https://peps.python.org/pep-0695/)
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[type aliases][type-aliases]. Can be one of:
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- `'skip'`: Do not try to parse type aliases. Note that this can lead to incorrect results:
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```pycon
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>>> type MyAlias = Literal[1, 2]
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>>> list(get_literal_values(Literal[MyAlias, 3], unpack_type_aliases="skip"))
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[MyAlias, 3]
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```
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- `'lenient'`: Try to parse type aliases, and fallback to `'skip'` if the type alias can't be inspected
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(because of an undefined forward reference).
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- `'eager'`: Parse type aliases and raise any encountered [`NameError`][] exceptions (the default):
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```pycon
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>>> type MyAlias = Literal[1, 2]
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>>> list(get_literal_values(Literal[MyAlias, 3], unpack_type_aliases="eager"))
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[1, 2, 3]
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```
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Note:
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While `None` is [equivalent to][none] `type(None)`, the runtime implementation of [`Literal`][typing.Literal]
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does not de-duplicate them. This function makes sure this de-duplication is applied:
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```pycon
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>>> list(get_literal_values(Literal[NoneType, None]))
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[None]
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```
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Example:
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```pycon
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>>> type Ints = Literal[1, 2]
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>>> list(get_literal_values(Literal[1, Ints], unpack_type_alias="skip"))
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["a", Ints]
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>>> list(get_literal_values(Literal[1, Ints]))
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[1, 2]
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>>> list(get_literal_values(Literal[1.0], type_check=True))
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Traceback (most recent call last):
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...
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TypeError: 1.0 is not a valid literal value, must be one of: int, bytes, str, Enum, None.
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```
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"""
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# `literal` is guaranteed to be a `Literal[...]` special form, so use
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# `__args__` directly instead of calling `get_args()`.
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if unpack_type_aliases == 'skip':
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_has_none = False
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# `Literal` parameters are already deduplicated, no need to do it ourselves.
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# (we only check for `None` and `NoneType`, which should be considered as duplicates).
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for arg in annotation.__args__:
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if type_check:
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_literal_type_check(arg)
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if arg is None or arg is typing_objects.NoneType:
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if not _has_none:
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yield None
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_has_none = True
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else:
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yield arg
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else:
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# We'll need to manually deduplicate parameters, see the `Literal` implementation in `typing`.
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values_and_type: list[tuple[Any, type[Any]]] = []
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for arg in annotation.__args__:
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# Note: we could also check for generic aliases with a type alias as an origin.
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# However, it is very unlikely that this happens as type variables can't appear in
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# `Literal` forms, so the only valid (but unnecessary) use case would be something like:
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# `type Test[T] = Literal['a']` (and then use `Test[SomeType]`).
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if typing_objects.is_typealiastype(arg):
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try:
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alias_value = arg.__value__
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except NameError:
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if unpack_type_aliases == 'eager':
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raise
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# unpack_type_aliases == "lenient":
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if type_check:
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_literal_type_check(arg)
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values_and_type.append((arg, type(arg)))
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else:
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sub_args = get_literal_values(
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alias_value, type_check=type_check, unpack_type_aliases=unpack_type_aliases
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)
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values_and_type.extend((a, type(a)) for a in sub_args) # pyright: ignore[reportUnknownArgumentType]
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else:
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if type_check:
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_literal_type_check(arg)
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if arg is typing_objects.NoneType:
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values_and_type.append((None, typing_objects.NoneType))
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else:
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values_and_type.append((arg, type(arg))) # pyright: ignore[reportUnknownArgumentType]
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try:
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dct = dict.fromkeys(values_and_type)
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except TypeError:
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# Unhashable parameters, the Python implementation allows them
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yield from (p for p, _ in values_and_type)
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else:
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yield from (p for p, _ in dct)
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Qualifier: TypeAlias = Literal['required', 'not_required', 'read_only', 'class_var', 'init_var', 'final']
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"""A [type qualifier][]."""
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_all_qualifiers: set[Qualifier] = set(get_args(Qualifier))
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# TODO at some point, we could switch to an enum flag, so that multiple sources
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# can be combined. However, is there a need for this?
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class AnnotationSource(IntEnum):
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# TODO if/when https://peps.python.org/pep-0767/ is accepted, add 'read_only'
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# to CLASS and NAMED_TUPLE (even though for named tuples it is redundant).
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"""The source of an annotation, e.g. a class or a function.
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Depending on the source, different [type qualifiers][type qualifier] may be (dis)allowed.
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"""
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ASSIGNMENT_OR_VARIABLE = auto()
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"""An annotation used in an assignment or variable annotation:
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```python
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x: Final[int] = 1
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y: Final[str]
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```
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**Allowed type qualifiers:** [`Final`][typing.Final].
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"""
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CLASS = auto()
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"""An annotation used in the body of a class:
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```python
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class Test:
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x: Final[int] = 1
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y: ClassVar[str]
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```
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**Allowed type qualifiers:** [`ClassVar`][typing.ClassVar], [`Final`][typing.Final].
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"""
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DATACLASS = auto()
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"""An annotation used in the body of a dataclass:
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```python
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@dataclass
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class Test:
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x: Final[int] = 1
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y: InitVar[str] = 'test'
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```
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**Allowed type qualifiers:** [`ClassVar`][typing.ClassVar], [`Final`][typing.Final], [`InitVar`][dataclasses-init-only-variables].
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""" # noqa: E501
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TYPED_DICT = auto()
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"""An annotation used in the body of a [`TypedDict`][typing.TypedDict]:
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```python
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class TD(TypedDict):
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x: Required[ReadOnly[int]]
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y: ReadOnly[NotRequired[str]]
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```
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**Allowed type qualifiers:** [`ReadOnly`][typing.ReadOnly], [`Required`][typing.Required],
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[`NotRequired`][typing.NotRequired].
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"""
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NAMED_TUPLE = auto()
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"""An annotation used in the body of a [`NamedTuple`][typing.NamedTuple].
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```python
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class NT(NamedTuple):
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x: int
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y: str
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```
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**Allowed type qualifiers:** none.
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"""
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FUNCTION = auto()
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"""An annotation used in a function, either for a parameter or the return value.
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```python
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def func(a: int) -> str:
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...
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```
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**Allowed type qualifiers:** none.
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"""
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ANY = auto()
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"""An annotation that might come from any source.
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**Allowed type qualifiers:** all.
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"""
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BARE = auto()
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"""An annotation that is inspected as is.
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**Allowed type qualifiers:** none.
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"""
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@property
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def allowed_qualifiers(self) -> set[Qualifier]:
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"""The allowed [type qualifiers][type qualifier] for this annotation source."""
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# TODO use a match statement when Python 3.9 support is dropped.
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if self is AnnotationSource.ASSIGNMENT_OR_VARIABLE:
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return {'final'}
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elif self is AnnotationSource.CLASS:
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return {'final', 'class_var'}
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elif self is AnnotationSource.DATACLASS:
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return {'final', 'class_var', 'init_var'}
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elif self is AnnotationSource.TYPED_DICT:
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return {'required', 'not_required', 'read_only'}
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elif self in (AnnotationSource.NAMED_TUPLE, AnnotationSource.FUNCTION, AnnotationSource.BARE):
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return set()
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elif self is AnnotationSource.ANY:
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return _all_qualifiers
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else: # pragma: no cover
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assert_never(self)
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class ForbiddenQualifier(Exception):
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"""The provided [type qualifier][] is forbidden."""
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qualifier: Qualifier
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"""The forbidden qualifier."""
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def __init__(self, qualifier: Qualifier, /) -> None:
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self.qualifier = qualifier
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class _UnknownTypeEnum(Enum):
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UNKNOWN = auto()
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def __str__(self) -> str:
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return 'UNKNOWN'
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def __repr__(self) -> str:
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return '<UNKNOWN>'
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UNKNOWN = _UnknownTypeEnum.UNKNOWN
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"""A sentinel value used when no [type expression][] is present."""
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_UnkownType: TypeAlias = Literal[_UnknownTypeEnum.UNKNOWN]
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"""The type of the [`UNKNOWN`][typing_inspection.introspection.UNKNOWN] sentinel value."""
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class InspectedAnnotation(NamedTuple):
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"""The result of the inspected annotation."""
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type: Any | _UnkownType
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"""The final [type expression][], with [type qualifiers][type qualifier] and annotated metadata stripped.
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If no type expression is available, the [`UNKNOWN`][typing_inspection.introspection.UNKNOWN] sentinel
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value is used instead. This is the case when a [type qualifier][] is used with no type annotation:
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```python
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ID: Final = 1
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class C:
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x: ClassVar = 'test'
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```
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"""
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qualifiers: set[Qualifier]
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"""The [type qualifiers][type qualifier] present on the annotation."""
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metadata: Sequence[Any]
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"""The annotated metadata."""
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def inspect_annotation( # noqa: PLR0915
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annotation: Any,
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/,
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*,
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annotation_source: AnnotationSource,
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unpack_type_aliases: Literal['skip', 'lenient', 'eager'] = 'skip',
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) -> InspectedAnnotation:
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"""Inspect an [annotation expression][], extracting any [type qualifier][] and metadata.
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An [annotation expression][] is a [type expression][] optionally surrounded by one or more
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[type qualifiers][type qualifier] or by [`Annotated`][typing.Annotated]. This function will:
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- Unwrap the type expression, keeping track of the type qualifiers.
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- Unwrap [`Annotated`][typing.Annotated] forms, keeping track of the annotated metadata.
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Args:
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annotation: The annotation expression to be inspected.
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annotation_source: The source of the annotation. Depending on the source (e.g. a class), different type
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qualifiers may be (dis)allowed. To allow any type qualifier, use
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[`AnnotationSource.ANY`][typing_inspection.introspection.AnnotationSource.ANY].
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unpack_type_aliases: What to do when encountering [PEP 695](https://peps.python.org/pep-0695/)
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[type aliases][type-aliases]. Can be one of:
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- `'skip'`: Do not try to parse type aliases (the default):
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```pycon
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>>> type MyInt = Annotated[int, 'meta']
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>>> inspect_annotation(MyInt, annotation_source=AnnotationSource.BARE, unpack_type_aliases='skip')
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InspectedAnnotation(type=MyInt, qualifiers={}, metadata=[])
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```
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- `'lenient'`: Try to parse type aliases, and fallback to `'skip'` if the type alias
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can't be inspected (because of an undefined forward reference):
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```pycon
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>>> type MyInt = Annotated[Undefined, 'meta']
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>>> inspect_annotation(MyInt, annotation_source=AnnotationSource.BARE, unpack_type_aliases='lenient')
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InspectedAnnotation(type=MyInt, qualifiers={}, metadata=[])
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>>> Undefined = int
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>>> inspect_annotation(MyInt, annotation_source=AnnotationSource.BARE, unpack_type_aliases='lenient')
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InspectedAnnotation(type=int, qualifiers={}, metadata=['meta'])
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```
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- `'eager'`: Parse type aliases and raise any encountered [`NameError`][] exceptions.
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Returns:
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The result of the inspected annotation, where the type expression, used qualifiers and metadata is stored.
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Example:
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```pycon
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>>> inspect_annotation(
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... Final[Annotated[ClassVar[Annotated[int, 'meta_1']], 'meta_2']],
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... annotation_source=AnnotationSource.CLASS,
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... )
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...
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InspectedAnnotation(type=int, qualifiers={'class_var', 'final'}, metadata=['meta_1', 'meta_2'])
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```
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"""
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allowed_qualifiers = annotation_source.allowed_qualifiers
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qualifiers: set[Qualifier] = set()
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metadata: list[Any] = []
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while True:
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annotation, _meta = _unpack_annotated(annotation, unpack_type_aliases=unpack_type_aliases)
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if _meta:
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metadata = _meta + metadata
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continue
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origin = get_origin(annotation)
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if origin is not None:
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if typing_objects.is_classvar(origin):
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if 'class_var' not in allowed_qualifiers:
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raise ForbiddenQualifier('class_var')
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qualifiers.add('class_var')
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annotation = annotation.__args__[0]
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elif typing_objects.is_final(origin):
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if 'final' not in allowed_qualifiers:
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raise ForbiddenQualifier('final')
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qualifiers.add('final')
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annotation = annotation.__args__[0]
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elif typing_objects.is_required(origin):
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if 'required' not in allowed_qualifiers:
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raise ForbiddenQualifier('required')
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qualifiers.add('required')
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annotation = annotation.__args__[0]
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elif typing_objects.is_notrequired(origin):
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if 'not_required' not in allowed_qualifiers:
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raise ForbiddenQualifier('not_required')
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qualifiers.add('not_required')
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annotation = annotation.__args__[0]
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elif typing_objects.is_readonly(origin):
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if 'read_only' not in allowed_qualifiers:
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raise ForbiddenQualifier('not_required')
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qualifiers.add('read_only')
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annotation = annotation.__args__[0]
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else:
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# origin is not None but not a type qualifier nor `Annotated` (e.g. `list[int]`):
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break
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elif isinstance(annotation, InitVar):
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if 'init_var' not in allowed_qualifiers:
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raise ForbiddenQualifier('init_var')
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qualifiers.add('init_var')
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annotation = cast(Any, annotation.type)
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else:
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break
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# `Final`, `ClassVar` and `InitVar` are type qualifiers allowed to be used as a bare annotation:
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if typing_objects.is_final(annotation):
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if 'final' not in allowed_qualifiers:
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raise ForbiddenQualifier('final')
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qualifiers.add('final')
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annotation = UNKNOWN
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elif typing_objects.is_classvar(annotation):
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if 'class_var' not in allowed_qualifiers:
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raise ForbiddenQualifier('class_var')
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qualifiers.add('class_var')
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annotation = UNKNOWN
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elif annotation is InitVar:
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if 'init_var' not in allowed_qualifiers:
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raise ForbiddenQualifier('init_var')
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qualifiers.add('init_var')
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annotation = UNKNOWN
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return InspectedAnnotation(annotation, qualifiers, metadata)
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def _unpack_annotated_inner(
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annotation: Any, unpack_type_aliases: Literal['lenient', 'eager'], check_annotated: bool
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) -> tuple[Any, list[Any]]:
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origin = get_origin(annotation)
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if check_annotated and typing_objects.is_annotated(origin):
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annotated_type = annotation.__origin__
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metadata = list(annotation.__metadata__)
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# The annotated type might be a PEP 695 type alias, so we need to recursively
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# unpack it. Because Python already flattens `Annotated[Annotated[<type>, ...], ...]` forms,
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# we can skip the `is_annotated()` check in the next call:
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annotated_type, sub_meta = _unpack_annotated_inner(
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annotated_type, unpack_type_aliases=unpack_type_aliases, check_annotated=False
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)
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metadata = sub_meta + metadata
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return annotated_type, metadata
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elif typing_objects.is_typealiastype(annotation):
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try:
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value = annotation.__value__
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except NameError:
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if unpack_type_aliases == 'eager':
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raise
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else:
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typ, metadata = _unpack_annotated_inner(
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value, unpack_type_aliases=unpack_type_aliases, check_annotated=True
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)
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if metadata:
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# Having metadata means the type alias' `__value__` was an `Annotated` form
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# (or, recursively, a type alias to an `Annotated` form). It is important to check
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# for this, as we don't want to unpack other type aliases (e.g. `type MyInt = int`).
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|
return typ, metadata
|
|
return annotation, []
|
|
elif typing_objects.is_typealiastype(origin):
|
|
# When parameterized, PEP 695 type aliases become generic aliases
|
|
# (e.g. with `type MyList[T] = Annotated[list[T], ...]`, `MyList[int]`
|
|
# is a generic alias).
|
|
try:
|
|
value = origin.__value__
|
|
except NameError:
|
|
if unpack_type_aliases == 'eager':
|
|
raise
|
|
else:
|
|
# While Python already handles type variable replacement for simple `Annotated` forms,
|
|
# we need to manually apply the same logic for PEP 695 type aliases:
|
|
# - With `MyList = Annotated[list[T], ...]`, `MyList[int] == Annotated[list[int], ...]`
|
|
# - With `type MyList[T] = Annotated[list[T], ...]`, `MyList[int].__value__ == Annotated[list[T], ...]`.
|
|
|
|
try:
|
|
# To do so, we emulate the parameterization of the value with the arguments:
|
|
# with `type MyList[T] = Annotated[list[T], ...]`, to emulate `MyList[int]`,
|
|
# we do `Annotated[list[T], ...][int]` (which gives `Annotated[list[T], ...]`):
|
|
value = value[annotation.__args__]
|
|
except TypeError:
|
|
# Might happen if the type alias is parameterized, but its value doesn't have any
|
|
# type variables, e.g. `type MyInt[T] = int`.
|
|
pass
|
|
typ, metadata = _unpack_annotated_inner(
|
|
value, unpack_type_aliases=unpack_type_aliases, check_annotated=True
|
|
)
|
|
if metadata:
|
|
return typ, metadata
|
|
return annotation, []
|
|
|
|
return annotation, []
|
|
|
|
|
|
# This could eventually be made public:
|
|
def _unpack_annotated(
|
|
annotation: Any, /, *, unpack_type_aliases: Literal['skip', 'lenient', 'eager'] = 'eager'
|
|
) -> tuple[Any, list[Any]]:
|
|
if unpack_type_aliases == 'skip':
|
|
if typing_objects.is_annotated(get_origin(annotation)):
|
|
return annotation.__origin__, list(annotation.__metadata__)
|
|
else:
|
|
return annotation, []
|
|
|
|
return _unpack_annotated_inner(annotation, unpack_type_aliases=unpack_type_aliases, check_annotated=True)
|