Make @particle_input compatible with from __future__ import annotations

changelog/2479.bugfix.rst

@@ -0,0 +1,2 @@
+Fixed a bug so that |particle_input| now works when a module begins
+with py:`from future import annotations`.

plasmapy/particles/decorators.py

@@ -9,7 +9,7 @@
 from collections.abc import Callable, Iterable, MutableMapping
 from inspect import BoundArguments
 from numbers import Integral, Real
-from typing import Any, Optional, TypedDict, Union
+from typing import Any, Optional, TypedDict, Union, get_type_hints
 
 import numpy as np
 import wrapt
@@ -57,19 +57,6 @@ class _CallableDataDict(TypedDict, total=False):
 )
 
 
-def _get_annotations(callable_: Callable[..., Any]) -> dict[str, Any]:
-    """
-    Access the annotations of a callable.
-
-    .. note::
-
-       For Python 3.10+, this should be replaced with
-       `inspect.get_annotations`.
-    """
-    # Python 3.10: Replace this with inspect.get_annotations
-    return getattr(callable_, "__annotations__", {})
-
-
 def _make_into_set_or_none(obj: Any) -> Optional[Iterable[str]]:
     """
     Return `None` if ``obj`` is `None`, and otherwise convert ``obj``
@@ -221,7 +208,7 @@ def callable_(self) -> Callable[..., Any]:
     @callable_.setter
     def callable_(self, callable_: Callable[..., Any]) -> None:
         self._data["callable_"] = callable_
-        self._data["annotations"] = _get_annotations(callable_)
+        self._data["annotations"] = get_type_hints(callable_)
         self._data["parameters_to_process"] = self.find_parameters_to_process()
         self._data["signature"] = inspect.signature(callable_)
 

plasmapy/particles/tests/test_decorators_future_annotations.py

@@ -0,0 +1,44 @@
+"""Tests for ``@particle_input`` with delayed evaluation of annotations."""
+
+# These tests must be in their own file because the `from __future__`
+# import must be at the top.
+from __future__ import annotations
+
+from plasmapy.particles.decorators import particle_input
+from plasmapy.particles.particle_class import Particle, ParticleLike
+
+
+@particle_input
+def function_decorated_with_particle_input(particle: ParticleLike) -> Particle:
+    return particle  # type: ignore[return-value]
+
+
+class DecoratedClass:
+    @particle_input
+    def __init__(self, particle: ParticleLike) -> None:
+        self.particle = particle
+
+
+class UndecoratedClass:
+    @particle_input
+    def decorated_method(self, particle: ParticleLike) -> Particle:
+        return particle  # type: ignore[return-value]
+
+
+def test_particle_input_from_future_import_annotations_function() -> None:
+    particle = function_decorated_with_particle_input("p+")
+    assert particle == Particle("p+")
+
+
+def test_particle_input_from_future_import_annotations_instantiation() -> None:
+    instance = DecoratedClass("p+")
+
+    assert isinstance(instance.particle, Particle)
+    assert instance.particle == Particle("p+")
+
+
+def test_particle_input_from_future_import_annotations_method() -> None:
+    instance = UndecoratedClass()
+    result = instance.decorated_method(particle="p+")
+    assert isinstance(result, Particle)
+    assert result == Particle("p+")