fixtures register finalizers with all fixtures before them in the stack

AUTHORS

@@ -55,6 +55,7 @@ Charles Cloud
 Charles Machalow
 Charnjit SiNGH (CCSJ)
 Chris Lamb
+Chris NeJame
 Christian Boelsen
 Christian Fetzer
 Christian Neumüller

changelog/6436.bugfix.rst

@@ -0,0 +1,3 @@
+:class:`FixtureDef <_pytest.fixtures.FixtureDef>` objects now properly register their finalizers with autouse and
+parameterized fixtures that execute before them in the fixture stack so they are torn
+down at the right times, and in the right order.

src/_pytest/fixtures.py

@@ -886,9 +886,7 @@ def finish(self, request):
             self._finalizers = []
 
     def execute(self, request):
-        # get required arguments and register our own finish()
-        # with their finalization
-        for argname in self.argnames:
+        for argname in self._dependee_fixture_argnames(request):
             fixturedef = request._get_active_fixturedef(argname)
             if argname != "request":
                 fixturedef.addfinalizer(functools.partial(self.finish, request=request))
@@ -912,6 +910,61 @@ def execute(self, request):
         hook = self._fixturemanager.session.gethookproxy(request.node.fspath)
         return hook.pytest_fixture_setup(fixturedef=self, request=request)
 
+    def _dependee_fixture_argnames(self, request):
+        """A list of argnames for fixtures that this fixture depends on.
+
+        Given a request, this looks at the currently known list of fixture argnames, and
+        attempts to determine what slice of the list contains fixtures that it can know
+        should execute before it. This information is necessary so that this fixture can
+        know what fixtures to register its finalizer with to make sure that if they
+        would be torn down, they would tear down this fixture before themselves. It's
+        crucial for fixtures to be torn down in the inverse order that they were set up
+        in so that they don't try to clean up something that another fixture is still
+        depending on.
+
+        When autouse fixtures are involved, it can be tricky to figure out when fixtures
+        should be torn down. To solve this, this method leverages the ``fixturenames``
+        list provided by the ``request`` object, as this list is at least somewhat
+        sorted (in terms of the order fixtures are set up in) by the time this method is
+        reached. It's sorted enough that the starting point of fixtures that depend on
+        this one can be found using the ``self._parent_request`` stack.
+
+        If a request in the ``self._parent_request`` stack has a ``:class:FixtureDef``
+        associated with it, then that fixture is dependent on this one, so any fixture
+        names that appear in the list of fixture argnames that come after it can also be
+        ruled out. The argnames of all fixtures associated with a request in the
+        ``self._parent_request`` stack are found, and the lowest index argname is
+        considered the earliest point in the list of fixture argnames where everything
+        from that point onward can be considered to execute after this fixture.
+        Everything before this point can be considered fixtures that this fixture
+        depends on, and so this fixture should register its finalizer with all of them
+        to ensure that if any of them are to be torn down, they will tear this fixture
+        down first.
+
+        This is the first part of the list of fixture argnames that is returned. The last
+        part of the list is everything in ``self.argnames`` as those are explicit
+        dependees of this fixture, so this fixture should definitely register its
+        finalizer with them.
+        """
+        all_fix_names = request.fixturenames
+        try:
+            current_fix_index = all_fix_names.index(self.argname)
+        except ValueError:
+            current_fix_index = len(request.fixturenames)
+        parent_fixture_indexes = set()
+
+        parent_request = request._parent_request
+        while hasattr(parent_request, "_parent_request"):
+            if hasattr(parent_request, "_fixturedef"):
+                parent_fix_name = parent_request._fixturedef.argname
+                if parent_fix_name in all_fix_names:
+                    parent_fixture_indexes.add(all_fix_names.index(parent_fix_name))
+            parent_request = parent_request._parent_request
+
+        stack_slice_index = min([current_fix_index, *parent_fixture_indexes])
+        active_fixture_argnames = all_fix_names[:stack_slice_index]
+        return {*active_fixture_argnames, *self.argnames}
+
     def cache_key(self, request):
         return request.param_index if not hasattr(request, "param") else request.param
 

testing/python/fixtures.py

@@ -1748,6 +1748,138 @@ def test_world(self):
         reprec.assertoutcome(passed=3)
 
 
+class TestMultiLevelAutouseAndParameterization:
+    def test_setup_and_teardown_order(self, testdir):
+        """Tests that parameterized fixtures effect subsequent fixtures. (#6436)
+
+        If a fixture uses a parameterized fixture, or, for any other reason, is executed
+        after the parameterized fixture in the fixture stack, then it should be affected
+        by the parameterization, and as a result, should be torn down before the
+        parameterized fixture, every time the parameterized fixture is torn down. This
+        should be the case even if autouse is involved and/or the linear order of
+        fixture execution isn't deterministic. In other words, before any fixture can be
+        torn down, every fixture that was executed after it must also be torn down.
+        """
+        testdir.makepyfile(
+            test_auto="""
+            import pytest
+            def f(param):
+                return param
+            @pytest.fixture(scope="session", autouse=True)
+            def s_fix(request):
+                yield
+            @pytest.fixture(scope="package", params=["p1", "p2"], ids=f, autouse=True)
+            def p_fix(request):
+                yield
+            @pytest.fixture(scope="module", params=["m1", "m2"], ids=f, autouse=True)
+            def m_fix(request):
+                yield
+            @pytest.fixture(scope="class", autouse=True)
+            def another_c_fix(m_fix):
+                yield
+            @pytest.fixture(scope="class")
+            def c_fix():
+                yield
+            @pytest.fixture(scope="function", params=["f1", "f2"], ids=f, autouse=True)
+            def f_fix(request):
+                yield
+            class TestFixtures:
+                def test_a(self, c_fix):
+                    pass
+                def test_b(self, c_fix):
+                    pass
+        """
+        )
+        result = testdir.runpytest("--setup-plan")
+        test_fixtures_used = (
+            "(fixtures used: another_c_fix, c_fix, f_fix, m_fix, p_fix, request, s_fix)"
+        )
+        result.stdout.fnmatch_lines(
+            """
+            SETUP    S s_fix
+              SETUP    P p_fix[p1]
+                SETUP    M m_fix[m1]
+                  SETUP    C another_c_fix (fixtures used: m_fix)
+                  SETUP    C c_fix
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_a[p1-m1-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_a[p1-m1-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_b[p1-m1-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_b[p1-m1-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                  TEARDOWN C c_fix
+                  TEARDOWN C another_c_fix
+                TEARDOWN M m_fix[m1]
+                SETUP    M m_fix[m2]
+                  SETUP    C another_c_fix (fixtures used: m_fix)
+                  SETUP    C c_fix
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_a[p1-m2-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_a[p1-m2-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_b[p1-m2-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_b[p1-m2-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                  TEARDOWN C c_fix
+                  TEARDOWN C another_c_fix
+                TEARDOWN M m_fix[m2]
+              TEARDOWN P p_fix[p1]
+              SETUP    P p_fix[p2]
+                SETUP    M m_fix[m1]
+                  SETUP    C another_c_fix (fixtures used: m_fix)
+                  SETUP    C c_fix
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_a[p2-m1-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_a[p2-m1-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_b[p2-m1-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_b[p2-m1-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                  TEARDOWN C c_fix
+                  TEARDOWN C another_c_fix
+                TEARDOWN M m_fix[m1]
+                SETUP    M m_fix[m2]
+                  SETUP    C another_c_fix (fixtures used: m_fix)
+                  SETUP    C c_fix
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_a[p2-m2-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_a[p2-m2-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                    SETUP    F f_fix[f1]
+                    test_auto.py::TestFixtures::test_b[p2-m2-f1] {0}
+                    TEARDOWN F f_fix[f1]
+                    SETUP    F f_fix[f2]
+                    test_auto.py::TestFixtures::test_b[p2-m2-f2] {0}
+                    TEARDOWN F f_fix[f2]
+                  TEARDOWN C c_fix
+                  TEARDOWN C another_c_fix
+                TEARDOWN M m_fix[m2]
+              TEARDOWN P p_fix[p2]
+            TEARDOWN S s_fix
+        """.format(
+                test_fixtures_used
+            )
+        )
+
+
 class TestAutouseManagement:
     def test_autouse_conftest_mid_directory(self, testdir):
         pkgdir = testdir.mkpydir("xyz123")