pdoc.doc_types

  1"""
  2This module handles all interpretation of type annotations in pdoc.
  3
  4In particular, it provides functionality to resolve
  5[typing.ForwardRef](https://docs.python.org/3/library/typing.html#typing.ForwardRef) objects without raising an
  6exception.
  7"""
  8from __future__ import annotations
  9
 10import functools
 11import inspect
 12import operator
 13import sys
 14import types
 15import typing
 16import warnings
 17from types import BuiltinFunctionType
 18from types import ModuleType
 19from typing import _GenericAlias  # type: ignore
 20from typing import Any
 21from typing import TYPE_CHECKING
 22
 23from . import extract
 24from ._compat import GenericAlias
 25from ._compat import get_origin
 26from ._compat import Literal
 27from ._compat import UnionType
 28from .doc_ast import type_checking_sections
 29
 30if TYPE_CHECKING:
 31
 32    class empty:
 33        pass
 34
 35
 36empty = inspect.Signature.empty  # type: ignore  # noqa
 37"""
 38A "special" object signaling the absence of a type annotation. 
 39This is useful to distinguish it from an actual annotation with `None`.
 40This value is an alias of `inspect.Signature.empty`.
 41"""
 42
 43# adapted from
 44# https://github.com/python/cpython/blob/9feae41c4f04ca27fd2c865807a5caeb50bf4fc4/Lib/inspect.py#L1740-L1747
 45# ✂ start ✂
 46_WrapperDescriptor = type(type.__call__)
 47_MethodWrapper = type(all.__call__)  # type: ignore
 48_ClassMethodWrapper = type(int.__dict__["from_bytes"])
 49
 50NonUserDefinedCallables = (
 51    _WrapperDescriptor,
 52    _MethodWrapper,
 53    _ClassMethodWrapper,
 54    BuiltinFunctionType,
 55)
 56
 57
 58# ✂ end ✂
 59
 60
 61def resolve_annotations(
 62    annotations: dict[str, Any],
 63    module: ModuleType | None,
 64    localns: dict[str, Any] | None,
 65    fullname: str,
 66) -> dict[str, Any]:
 67    """
 68    Given an `annotations` dictionary with type annotations (for example, `cls.__annotations__`),
 69    this function tries to resolve all types using `pdoc.doc_types.safe_eval_type`.
 70
 71    Returns: A dictionary with the evaluated types.
 72    """
 73    globalns = getattr(module, "__dict__", {})
 74
 75    resolved = {}
 76    for name, value in annotations.items():
 77        resolved[name] = safe_eval_type(
 78            value, globalns, localns, module, f"{fullname}.{name}"
 79        )
 80
 81    return resolved
 82
 83
 84def safe_eval_type(
 85    t: Any,
 86    globalns: dict[str, Any],
 87    localns: dict[str, Any] | None,
 88    module: types.ModuleType | None,
 89    fullname: str,
 90) -> Any:
 91    """
 92    This method wraps `typing._eval_type`, but doesn't raise on errors.
 93    It is used to evaluate a type annotation, which might already be
 94    a proper type (in which case no action is required), or a forward reference string,
 95    which needs to be resolved.
 96
 97    If _eval_type fails, we try some heuristics to import a missing module.
 98    If that still fails, a warning is emitted and `t` is returned as-is.
 99    """
100    try:
101        return _eval_type(t, globalns, localns)
102    except AttributeError as e:
103        err = str(e)
104        _, obj, _, attr, _ = err.split("'")
105        mod = f"{obj}.{attr}"
106    except NameError as e:
107        err = str(e)
108        _, mod, _ = err.split("'")
109    except Exception as e:
110        if "unsupported operand type(s) for |" in str(e) and sys.version_info < (3, 10):
111            py_ver = ".".join(str(x) for x in sys.version_info[:3])
112            warnings.warn(
113                f"Error parsing type annotation {t} for {fullname}: {e}. "
114                f"You are likely attempting to use Python 3.10 syntax (PEP 604 union types) with an older Python "
115                f"release. `X | Y`-style type annotations are invalid syntax on Python {py_ver}, which is what your "
116                f"pdoc instance is using. `from future import __annotations__` (PEP 563) postpones evaluation of "
117                f"annotations, which is why your program won't crash right away. However, pdoc needs to evaluate your "
118                f"type annotations and is unable to do so on Python {py_ver}. To fix this issue, either invoke pdoc "
119                f"from Python 3.10+, or switch to `typing.Union[]` syntax."
120            )
121        else:
122            warnings.warn(f"Error parsing type annotation {t} for {fullname}: {e}")
123        return t
124
125    # Simple _eval_type has failed. We now execute all TYPE_CHECKING sections in the module and try again.
126    if module:
127        try:
128            code = compile(type_checking_sections(module), "<string>", "exec")
129            eval(code, globalns, globalns)
130        except Exception as e:
131            warnings.warn(
132                f"Failed to run TYPE_CHECKING code while parsing {t} type annotation for {fullname}: {e}"
133            )
134        try:
135            return _eval_type(t, globalns, None)
136        except (AttributeError, NameError):
137            pass  # still not found
138        except Exception as e:
139            warnings.warn(
140                f"Error parsing type annotation {t} for {fullname} after evaluating TYPE_CHECKING blocks: {e}"
141            )
142            return t
143
144    try:
145        val = extract.load_module(mod)
146    except Exception:
147        warnings.warn(
148            f"Error parsing type annotation {t} for {fullname}. Import of {mod} failed: {err}"
149        )
150        return t
151    return safe_eval_type(t, {mod: val, **globalns}, localns, module, fullname)
152
153
154def _eval_type(t, globalns, localns, recursive_guard=frozenset()):
155    # Adapted from typing._eval_type.
156    # Added type coercion originally found in get_type_hints, but removed NoneType check because that was distracting.
157    # Added a special check for typing.Literal, whose literal strings would otherwise be evaluated.
158
159    if isinstance(t, str):
160        if sys.version_info < (3, 9):  # pragma: no cover
161            t = t.strip("\"'")
162        t = typing.ForwardRef(t)
163
164    if get_origin(t) is Literal:
165        return t
166
167    if isinstance(t, typing.ForwardRef):
168        # inlined from
169        # https://github.com/python/cpython/blob/4f51fa9e2d3ea9316e674fb9a9f3e3112e83661c/Lib/typing.py#L684-L707
170        if t.__forward_arg__ in recursive_guard:  # pragma: no cover
171            return t
172        if not t.__forward_evaluated__ or localns is not globalns:
173            if globalns is None and localns is None:  # pragma: no cover
174                globalns = localns = {}
175            elif globalns is None:  # pragma: no cover
176                globalns = localns
177            elif localns is None:  # pragma: no cover
178                localns = globalns
179            __forward_module__ = getattr(t, "__forward_module__", None)
180            if __forward_module__ is not None:
181                globalns = getattr(
182                    sys.modules.get(__forward_module__, None), "__dict__", globalns
183                )
184            (type_,) = (eval(t.__forward_code__, globalns, localns),)
185            t.__forward_value__ = _eval_type(
186                type_, globalns, localns, recursive_guard | {t.__forward_arg__}
187            )
188            t.__forward_evaluated__ = True
189        return t.__forward_value__
190
191    # https://github.com/python/cpython/blob/main/Lib/typing.py#L333-L343
192    # fmt: off
193    # ✂ start ✂
194    if isinstance(t, (_GenericAlias, GenericAlias, UnionType)):
195        ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__)
196        if ev_args == t.__args__:
197            return t
198        if isinstance(t, GenericAlias):
199            return GenericAlias(t.__origin__, ev_args)
200        if isinstance(t, UnionType):
201            return functools.reduce(operator.or_, ev_args)
202        else:
203            return t.copy_with(ev_args)
204    return t
205    # ✂ end ✂