Fix fixture finalizers being skipped if setup is interrupted

changelog/15067.bugfix.rst

@@ -0,0 +1 @@
+Fix bug where fixture finalizers were skipped if fixture setup was interrupted before ``cached_result`` was set.

src/_pytest/fixtures.py

@@ -1204,7 +1204,7 @@ def addfinalizer(self, finalizer: Callable[[], object]) -> None:
         self._finalizers.append(finalizer)
 
     def finish(self, request: SubRequest) -> None:
-        if self.cached_result is None:
+        if self.cached_result is None and not self._finalizers:
             # Already finished. It is assumed that finalizers cannot be added in
             # this state.
             return
@@ -1216,6 +1216,7 @@ def finish(self, request: SubRequest) -> None:
                 fin()
             except BaseException as e:
                 exceptions.append(e)
+
         node = request.node
         # Even if finalization fails, we invalidate the cached fixture
         # value and remove all finalizers because they may be bound methods
@@ -1279,11 +1280,14 @@ def execute(self, request: SubRequest) -> FixtureValue:
         # Register the pytest_fixture_post_finalizer as the first finalizer,
         # which is executed last.
         assert not self._finalizers
-        self.addfinalizer(
-            lambda: request.node.ihook.pytest_fixture_post_finalizer(
-                fixturedef=self, request=request
-            )
-        )
+
+        def post_finalizer() -> None:
+            if self.cached_result is not None:
+                request.node.ihook.pytest_fixture_post_finalizer(
+                    fixturedef=self, request=request
+                )
+
+        self.addfinalizer(post_finalizer)
 
         ihook = request.node.ihook
         try:

testing/python/fixtures.py

@@ -6278,3 +6278,78 @@ def test_fixt(self, fixt):
     )
     result.stdout.fnmatch_lines(["*fixture 'fixt' not found*"])
     result.assert_outcomes(errors=1)
+
+
+def test_fixture_finalizer_interrupt(pytester: Pytester) -> None:
+    pytester.makeconftest(
+        """
+        import pytest
+        from pathlib import Path
+
+        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 == 2
+    assert (pytester.path / "finalizer-ran").exists()
+
+
+def test_fixture_post_finalizer_skipped_on_setup_failure(pytester: Pytester) -> None:
+    pytester.makeconftest(
+        """
+        import pytest
+        from pathlib import Path
+
+        @pytest.fixture
+        def broken_fixture(request):
+            request.addfinalizer(lambda: print("USER_FINALIZER_RAN"))
+            raise SystemExit("Setup interrupted!")
+
+        def pytest_fixture_post_finalizer(fixturedef, request):
+            print(f"POST_FINALIZER_RAN:{fixturedef.argname}:{fixturedef.cached_result is not None}")
+        """
+    )
+    pytester.makepyfile(
+        """
+        def test_setup(broken_fixture):
+            pass
+        """
+    )
+    result = pytester.runpytest("-s")
+    result.stdout.fnmatch_lines(["*USER_FINALIZER_RAN*"])
+    assert "POST_FINALIZER_RAN:broken_fixture" not in result.stdout.str()
+    assert "POST_FINALIZER_RAN:broken_fixture:False" not in result.stdout.str()
+
+
+def test_fixture_post_finalizer_adds_finalizer(pytester: Pytester) -> None:
+    pytester.makeconftest(
+        """
+        import pytest
+
+        @pytest.fixture
+        def my_fixture(request):
+            pass
+
+        def pytest_fixture_post_finalizer(fixturedef, request):
+            request.addfinalizer(lambda: print("DYNAMIC_FINALIZER_RAN"))
+        """
+    )
+    pytester.makepyfile(
+        """
+        def test_dynamic_finalizer(my_fixture):
+            pass
+        """
+    )
+    result = pytester.runpytest("-s")
+    result.stdout.fnmatch_lines(["*DYNAMIC_FINALIZER_RAN*"])