Cancel autouse fixture shadowed by non-autouse override

changelog/3225.bugfix.rst

@@ -0,0 +1 @@
+A non-autouse fixture overriding an autouse one no longer runs automatically.

src/_pytest/fixtures.py

@@ -1938,14 +1938,29 @@ def pytest_collection_finish(self) -> None:
 
     def _getautousenames(self, node: nodes.Node) -> Iterator[str]:
         """Return the names of autouse fixtures visible to node."""
+        usefixtures_ini = set(self.config.getini("usefixtures"))
         for parentnode in node.listchain():
             basenames = self._node_autousenames.get(parentnode)
             if basenames:
-                yield from basenames
+                for name in basenames:
+                    if name in usefixtures_ini or self._is_autouse(name, node):
+                        yield name
             # Legacy fallback: check string-based nodeid autouse names.
             nodeid_basenames = self._nodeid_autousenames.get(parentnode.nodeid)
             if nodeid_basenames:
-                yield from nodeid_basenames
+                for name in nodeid_basenames:
+                    if self._is_autouse(name, node):
+                        yield name
+
+    def _is_autouse(self, name: str, node: nodes.Node) -> bool:
+        """Whether the fixture resolved for name is itself autouse.
+
+        A non-autouse override cancels the autouse fixture it shadows (#3225).
+        """
+        fixturedefs = self.getfixturedefs(name, node)
+        if not fixturedefs:
+            return True
+        return fixturedefs[-1]._autouse
 
     def _getusefixturesnames(self, node: nodes.Item) -> Iterator[str]:
         """Return the names of usefixtures fixtures visible to node."""

testing/python/fixtures.py

@@ -2560,6 +2560,39 @@ def test_hello(arg1):
         reprec = pytester.inline_run()
         reprec.assertoutcome(passed=1)
 
+    def test_autouse_cancelled_by_non_autouse_override(
+        self, pytester: Pytester
+    ) -> None:
+        """A non-autouse override cancels the autouse fixture it shadows (#3225)."""
+        pytester.makeconftest(
+            """
+            import pytest
+
+            @pytest.fixture(autouse=True)
+            def foo():
+                pass
+            """
+        )
+        pytester.makepyfile(
+            """
+            import pytest
+
+            @pytest.fixture()
+            def foo():
+                assert False
+
+            def test_bar(foo):
+                pass
+
+            def test_baz():
+                pass
+            """
+        )
+        result = pytester.runpytest()
+        result.assert_outcomes(passed=1, errors=1)
+        result = pytester.runpytest("-o", "usefixtures=foo")
+        result.assert_outcomes(errors=2)
+
     @pytest.mark.parametrize("param1", ["", "params=[1]"], ids=["p00", "p01"])
     @pytest.mark.parametrize("param2", ["", "params=[1]"], ids=["p10", "p11"])
     def test_ordering_dependencies_torndown_first(