fix #13564 - warn when fixtures get wrapped with a decorator

.gitignore

@@ -57,3 +57,4 @@ pip-wheel-metadata/
 
 # pytest debug logs generated via --debug
 pytestdebug.log
+.claude/settings.local.json

changelog/13564.improvement.rst

@@ -0,0 +1,2 @@
+Issue a warning when fixtures are wrapped with a decorator, as that excludes
+them from being discovered safely by pytest.

src/_pytest/fixtures.py

@@ -1271,7 +1271,9 @@ def __init__(
     def __repr__(self) -> str:
         return f"<pytest_fixture({self._fixture_function})>"
 
-    def __get__(self, instance, owner=None):
+    def __get__(
+        self, instance: object, owner: type | None = None
+    ) -> FixtureFunctionDefinition:
         """Behave like a method if the function it was applied to was a method."""
         return FixtureFunctionDefinition(
             function=self._fixture_function,
@@ -1765,6 +1767,80 @@ def _register_fixture(
         if autouse:
             self._nodeid_autousenames.setdefault(nodeid or "", []).append(name)
 
+    def _find_wrapped_fixture_def(
+        self, obj: object
+    ) -> FixtureFunctionDefinition | None:
+        """Walk through wrapper chain to find a FixtureFunctionDefinition.
+
+        Returns the FixtureFunctionDefinition if found in the wrapper chain,
+        None otherwise. Handles loops and special objects safely.
+        """
+        from _pytest.compat import safe_getattr
+
+        # Skip mock objects (they have _mock_name attribute)
+        if safe_getattr(obj, "_mock_name", None) is not None:
+            return None
+
+        current = obj
+        seen = set()  # Track object IDs to detect loops
+        max_depth = 100  # Prevent infinite loops even if ID tracking fails
+
+        for _ in range(max_depth):
+            if current is None:
+                break
+
+            # Check for wrapper loops by object identity
+            current_id = id(current)
+            if current_id in seen:
+                return None
+            seen.add(current_id)
+
+            # Check if current is a FixtureFunctionDefinition
+            # Use try/except to handle objects with problematic __class__ properties
+            try:
+                if isinstance(current, FixtureFunctionDefinition):
+                    return current
+            except Exception:
+                # Can't check isinstance - probably a proxy object
+                return None
+
+            # Try to get the next wrapped object using safe_getattr to handle
+            # "evil objects" that raise on attribute access (see issue #214)
+            wrapped = safe_getattr(current, "__wrapped__", None)
+            if wrapped is None:
+                break
+
+            current = wrapped
+
+        return None
+
+    def _check_for_wrapped_fixture(
+        self, holder: object, name: str, obj: object, nodeid: str | None
+    ) -> None:
+        """Check if an object might be a fixture wrapped in decorators and warn if so."""
+        # Only check objects that are not None
+        if obj is None:
+            return
+
+        # Try to find a FixtureFunctionDefinition in the wrapper chain
+        fixture_def = self._find_wrapped_fixture_def(obj)
+
+        # If we found a fixture definition and it's not the top-level object,
+        # it means the fixture is wrapped in decorators
+        if fixture_def is not None and fixture_def is not obj:
+            fixture_func = fixture_def._get_wrapped_function()
+            self._issue_fixture_wrapped_warning(name, nodeid, fixture_func)
+
+    def _issue_fixture_wrapped_warning(
+        self, fixture_name: str, nodeid: str | None, fixture_func: Any
+    ) -> None:
+        """Issue a warning about a fixture that cannot be discovered due to decorators."""
+        from _pytest.warning_types import PytestWarning
+        from _pytest.warning_types import warn_explicit_for
+
+        msg = f"cannot discover {fixture_name} due to being wrapped in decorators"
+        warn_explicit_for(fixture_func, PytestWarning(msg))
+
     @overload
     def parsefactories(
         self,
@@ -1845,6 +1921,9 @@ def parsefactories(
                     ids=marker.ids,
                     autouse=marker.autouse,
                 )
+            else:
+                # Check if this might be a wrapped fixture that we can't discover
+                self._check_for_wrapped_fixture(holderobj, name, obj_ub, nodeid)
 
     def getfixturedefs(
         self, argname: str, node: nodes.Node

testing/python/fixtures.py

@@ -5069,3 +5069,49 @@ def test_method(self, /, fix):
     )
     result = pytester.runpytest()
     result.assert_outcomes(passed=1)
+
+
+@pytest.mark.filterwarnings(
+    "default:cannot discover * due to being wrapped in decorators:pytest.PytestWarning"
+)
+def test_custom_decorated_fixture_warning(pytester: Pytester) -> None:
+    """
+    Test that fixtures decorated with custom decorators using functools.wraps
+    generate a warning about not being discoverable.
+    """
+    pytester.makepyfile(
+        """
+        import pytest
+        import functools
+
+        def custom_deco(func):
+            @functools.wraps(func)
+            def wrapper(*args, **kwargs):
+                return func(*args, **kwargs)
+            return wrapper
+
+        class TestClass:
+            @custom_deco
+            @pytest.fixture
+            def my_fixture(self):
+                return "fixture_value"
+
+            def test_fixture_usage(self, my_fixture):
+                assert my_fixture == "fixture_value"
+        """
+    )
+    result = pytester.runpytest_inprocess(
+        "-v", "-rw", "-W", "default::pytest.PytestWarning"
+    )
+
+    # Should get a warning about the decorated fixture during collection with correct location
+    result.stdout.fnmatch_lines(
+        [
+            "*test_custom_decorated_fixture_warning.py:*: "
+            "PytestWarning: cannot discover my_fixture due to being wrapped in decorators*"
+        ]
+    )
+
+    # The test should fail because fixture is not found
+    result.stdout.fnmatch_lines(["*fixture 'my_fixture' not found*"])
+    result.assert_outcomes(errors=1)