Defer annotation eval on Python 3.14 (#13550) (#13553)

Fixes #13549

(cherry picked from commit 8ca783c)

Co-authored-by: Marc Mueller <[email protected]>

Author: patchback[bot]

changelog/13549.bugfix.rst

@@ -0,0 +1,3 @@
+No longer evaluate type annotations in Python ``3.14`` when inspecting function signatures.
+
+This prevents crashes during module collection when modules do not explicitly use ``from __future__ import annotations`` and import types for annotations within a ``if TYPE_CHECKING:`` block.

src/_pytest/compat.py

@@ -8,7 +8,7 @@
 import functools
 import inspect
 from inspect import Parameter
-from inspect import signature
+from inspect import Signature
 import os
 from pathlib import Path
 import sys
@@ -19,6 +19,10 @@
 import py
 
 
+if sys.version_info >= (3, 14):
+    from annotationlib import Format
+
+
 #: constant to prepare valuing pylib path replacements/lazy proxies later on
 #  intended for removal in pytest 8.0 or 9.0
 
@@ -60,6 +64,13 @@ def is_async_function(func: object) -> bool:
     return iscoroutinefunction(func) or inspect.isasyncgenfunction(func)
 
 
+def signature(obj: Callable[..., Any]) -> Signature:
+    """Return signature without evaluating annotations."""
+    if sys.version_info >= (3, 14):
+        return inspect.signature(obj, annotation_format=Format.STRING)
+    return inspect.signature(obj)
+
+
 def getlocation(function, curdir: str | os.PathLike[str] | None = None) -> str:
     function = get_real_func(function)
     fn = Path(inspect.getfile(function))

src/_pytest/fixtures.py

@@ -49,6 +49,7 @@
 from _pytest.compat import NotSetType
 from _pytest.compat import safe_getattr
 from _pytest.compat import safe_isclass
+from _pytest.compat import signature
 from _pytest.config import _PluggyPlugin
 from _pytest.config import Config
 from _pytest.config import ExitCode
@@ -804,8 +805,8 @@ def _format_fixturedef_line(self, fixturedef: FixtureDef[object]) -> str:
         path, lineno = getfslineno(factory)
         if isinstance(path, Path):
             path = bestrelpath(self._pyfuncitem.session.path, path)
-        signature = inspect.signature(factory)
-        return f"{path}:{lineno + 1}:  def {factory.__name__}{signature}"
+        sig = signature(factory)
+        return f"{path}:{lineno + 1}:  def {factory.__name__}{sig}"
 
     def addfinalizer(self, finalizer: Callable[[], object]) -> None:
         self._fixturedef.addfinalizer(finalizer)

src/_pytest/nodes.py

@@ -8,7 +8,6 @@
 from collections.abc import MutableMapping
 from functools import cached_property
 from functools import lru_cache
-from inspect import signature
 import os
 import pathlib
 from pathlib import Path
@@ -29,6 +28,7 @@
 from _pytest._code.code import Traceback
 from _pytest._code.code import TracebackStyle
 from _pytest.compat import LEGACY_PATH
+from _pytest.compat import signature
 from _pytest.config import Config
 from _pytest.config import ConftestImportFailure
 from _pytest.config.compat import _check_path

testing/test_collection.py

@@ -1895,3 +1895,43 @@ def test_with_yield():
     )
     # Assert that no tests were collected
     result.stdout.fnmatch_lines(["*collected 0 items*"])
+
+
+def test_annotations_deferred_future(pytester: Pytester):
+    """Ensure stringified annotations don't raise any errors."""
+    pytester.makepyfile(
+        """
+        from __future__ import annotations
+        import pytest
+
+        @pytest.fixture
+        def func() -> X: ...  # X is undefined
+
+        def test_func():
+            assert True
+        """
+    )
+    result = pytester.runpytest()
+    assert result.ret == 0
+    result.stdout.fnmatch_lines(["*1 passed*"])
+
+
+@pytest.mark.skipif(
+    sys.version_info < (3, 14), reason="Annotations are only skipped on 3.14+"
+)
+def test_annotations_deferred_314(pytester: Pytester):
+    """Ensure annotation eval is deferred."""
+    pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.fixture
+        def func() -> X: ...  # X is undefined
+
+        def test_func():
+            assert True
+        """
+    )
+    result = pytester.runpytest()
+    assert result.ret == 0
+    result.stdout.fnmatch_lines(["*1 passed*"])