Fix fixture discovery for bound methods in custom collectors

AUTHORS

@@ -346,6 +346,7 @@ Mike Lundy
 Mike Ma
 Milan Lesnek
 minbang930
+Minh Dau
 Miro Hrončok
 Mulat Mekonen
 mrbean-bremen

changelog/6750.bugfix.rst

@@ -0,0 +1 @@
+Fix fixture argument discovery for custom collectors that pass bound methods to :class:`pytest.Function`.

src/_pytest/compat.py

@@ -162,6 +162,7 @@ def getfuncargnames(
         # Not using `getattr` because we don't want to resolve the staticmethod.
         # Not using `cls.__dict__` because we want to check the entire MRO.
         cls
+        and not inspect.ismethod(function)
         and not isinstance(
             inspect.getattr_static(cls, name, default=None), staticmethod
         )

testing/python/fixtures.py

@@ -69,6 +69,52 @@ def k(self, /, arg1, *, arg2, arg3="hello"):
     assert getfuncargnames(A().k) == ("arg1", "arg2")
 
 
+def test_bound_method_fixtures_custom_collector(pytester: Pytester) -> None:
+    """Custom collectors can supply already-bound methods (#6750)."""
+    pytester.makeconftest(
+        """
+        import pytest
+
+        def pytest_pycollect_makeitem(collector, name, obj):
+            if isinstance(collector, pytest.Class) and name.startswith("test_"):
+                return pytest.Function.from_parent(
+                    collector,
+                    name=name,
+                    callobj=getattr(collector.newinstance(), name),
+                )
+        """
+    )
+    pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.fixture
+        def value():
+            return 42
+
+        class TestBound:
+            def test_instance(self, value):
+                assert value == 42
+
+            def test_positional_only_receiver(self, /, value):
+                assert value == 42
+
+            def test_keyword_only_fixture(self, *, value):
+                assert value == 42
+
+            @classmethod
+            def test_classmethod(cls, value):
+                assert value == 42
+
+            @staticmethod
+            def test_staticmethod(value):
+                assert value == 42
+        """
+    )
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=5)
+
+
 def test_getfuncargnames_staticmethod():
     """Test getfuncargnames for staticmethods"""