Fix fixture finalizers being skipped when setup is interrupted

changelog/15067.bugfix.rst

@@ -0,0 +1,4 @@
+Fixed fixture finalizers registered via ``request.addfinalizer()`` being skipped
+when fixture setup was interrupted (for example by ``KeyboardInterrupt`` or a
+fail-fast plugin) before the fixture value was cached. The interruption is now
+recorded so the registered finalizers still run during teardown, as documented.

src/_pytest/fixtures.py

@@ -1404,6 +1404,12 @@ def pytest_fixture_setup(
             e._use_item_location = True
         fixturedef.cached_result = (None, my_cache_key, (e, e.__traceback__))
         raise
+    except BaseException as e:
+        # Fixture setup was interrupted (e.g. by KeyboardInterrupt or a
+        # fail-fast plugin). Record the failure so that finalizers already
+        # registered via addfinalizer() still run during teardown (#15067).
+        fixturedef.cached_result = (None, my_cache_key, (e, e.__traceback__))
+        raise
     fixturedef.cached_result = (result, my_cache_key, None)
     return result
 

testing/python/fixtures.py

@@ -1111,6 +1111,71 @@ def test_fix(myfix):
         mod = reprec.getcalls("pytest_runtest_setup")[0].item.module
         assert not mod.values
 
+    def test_request_addfinalizer_interrupted_setup(self, pytester: Pytester) -> None:
+        """Ensure finalizers registered before fixture setup is interrupted
+        (e.g. by KeyboardInterrupt) still run during teardown (#15067)."""
+        pytester.makeconftest(
+            """
+            from pathlib import Path
+
+            import pytest
+
+            marker = Path(__file__).with_name("finalizer-ran")
+
+
+            @pytest.fixture
+            def resource(request):
+                request.addfinalizer(
+                    lambda: marker.write_text("ran", encoding="utf-8")
+                )
+                raise KeyboardInterrupt
+            """
+        )
+        pytester.makepyfile(
+            """
+            def test_setup(resource):
+                pass
+            """
+        )
+        result = pytester.runpytest_subprocess()
+        assert result.ret == ExitCode.INTERRUPTED
+        assert pytester.path.joinpath("finalizer-ran").exists()
+
+    def test_request_addfinalizer_interrupted_setup_inprocess(
+        self, pytester: Pytester
+    ) -> None:
+        """In-process variant of test_request_addfinalizer_interrupted_setup.
+
+        Runs the interrupted setup in-process so coverage observes the
+        ``except BaseException`` branch in ``pytest_fixture_setup`` (#15067).
+        """
+        pytester.makeconftest(
+            """
+            from pathlib import Path
+
+            import pytest
+
+            marker = Path(__file__).with_name("finalizer-ran-inprocess")
+
+
+            @pytest.fixture
+            def resource(request):
+                request.addfinalizer(
+                    lambda: marker.write_text("ran", encoding="utf-8")
+                )
+                raise KeyboardInterrupt
+            """
+        )
+        pytester.makepyfile(
+            """
+            def test_setup(resource):
+                pass
+            """
+        )
+        result = pytester.runpytest_inprocess(no_reraise_ctrlc=True)
+        assert result.ret == ExitCode.INTERRUPTED
+        assert pytester.path.joinpath("finalizer-ran-inprocess").exists()
+
     def test_request_addfinalizer_partial_setup_failure(
         self, pytester: Pytester
     ) -> None: