fixtures: fix crash when `parametrize(scope="package")` is used without a Package

There as handling for `scope="class"` without a class, but not for
`scope="package"` without a package. It would fail the assert.

changelog/11255.bugfix.rst

@@ -0,0 +1 @@
+Fixed crash on `parametrize(..., scope="package")` without a package present.

src/_pytest/fixtures.py

@@ -155,6 +155,8 @@ name2pseudofixturedef_key = StashKey[Dict[str, "FixtureDef[Any]"]]()
 def add_funcarg_pseudo_fixture_def(
     collector: nodes.Collector, metafunc: "Metafunc", fixturemanager: "FixtureManager"
 ) -> None:
+    import _pytest.python
+
     # This function will transform all collected calls to functions
     # if they use direct funcargs (i.e. direct parametrization)
     # because we want later test execution to be able to rely on
@@ -192,11 +194,17 @@ def add_funcarg_pseudo_fixture_def(
         if scope is not Scope.Function:
             node = get_scope_node(collector, scope)
             if node is None:
-                assert scope is Scope.Class and isinstance(
-                    collector, _pytest.python.Module
-                )
-                # Use module-level collector for class-scope (for now).
-                node = collector
+                # If used class scope and there is no class, use module-level
+                # collector (for now).
+                if scope is Scope.Class:
+                    assert isinstance(collector, _pytest.python.Module)
+                    node = collector
+                # If used package scope and there is no package, use session
+                # (for now).
+                elif scope is Scope.Package:
+                    node = collector.session
+                else:
+                    assert False, f"Unhandled missing scope: {scope}"
         if node is None:
             name2pseudofixturedef = None
         else:

testing/python/metafunc.py

@@ -1486,6 +1486,23 @@ class TestMetafuncFunctional:
             ]
         )
 
+    @pytest.mark.parametrize("scope", ["class", "package"])
+    def test_parametrize_missing_scope_doesnt_crash(
+        self, pytester: Pytester, scope: str
+    ) -> None:
+        """Doesn't crash when parametrize(scope=<scope>) is used without a
+        corresponding <scope> node."""
+        pytester.makepyfile(
+            f"""
+            import pytest
+
+            @pytest.mark.parametrize("x", [0], scope="{scope}")
+            def test_it(x): pass
+            """
+        )
+        result = pytester.runpytest()
+        assert result.ret == 0
+
 
 class TestMetafuncFunctionalAuto:
     """Tests related to automatically find out the correct scope for