Add is_pseudo & Replace the bad expression with isinstance check

src/_pytest/fixtures.py

@@ -882,7 +882,6 @@ def _eval_scope_callable(
     return result
 
 
-@final
 class FixtureDef(Generic[FixtureValue]):
     """A container for a fixture definition.
 
@@ -1025,6 +1024,24 @@ class FixtureDef(Generic[FixtureValue]):
         )
 
 
+class IdentityFixture(FixtureDef[FixtureValue]):
+    def __init__(
+        self,
+        fixturemanager: "FixtureManager",
+        argname: str,
+        scope: Union[Scope, _ScopeName, Callable[[str, Config], _ScopeName], None],
+    ):
+        super().__init__(
+            fixturemanager,
+            "",
+            argname,
+            lambda request: request.param,
+            scope,
+            None,
+            _ispytest=True,
+        )
+
+
 def resolve_fixture_function(
     fixturedef: FixtureDef[FixtureValue], request: FixtureRequest
 ) -> "_FixtureFunc[FixtureValue]":
@@ -1488,10 +1505,7 @@ class FixtureManager:
                         arg2fixturedefs[argname] = fixturedefs
                 else:
                     fixturedefs = arg2fixturedefs[argname]
-                if fixturedefs and not (
+                if fixturedefs and not isinstance(fixturedefs[-1], IdentityFixture):
-                    fixturedefs[-1].func.__name__ == "get_direct_param_fixture_func"
-                    and fixturedefs[-1].baseid == ""
-                ):
                     fixturenames_closure = deduplicate_names(
                         fixturenames_closure + arg2fixturedefs[argname][-1].argnames
                     )

src/_pytest/python.py

@@ -60,9 +60,9 @@ from _pytest.deprecated import INSTANCE_COLLECTOR
 from _pytest.deprecated import NOSE_SUPPORT_METHOD
 from _pytest.fixtures import _get_direct_parametrize_args
 from _pytest.fixtures import FixtureDef
-from _pytest.fixtures import FixtureRequest
 from _pytest.fixtures import FuncFixtureInfo
 from _pytest.fixtures import get_scope_node
+from _pytest.fixtures import IdentityFixture
 from _pytest.main import Session
 from _pytest.mark import MARK_GEN
 from _pytest.mark import ParameterSet
@@ -1184,10 +1184,6 @@ class CallSpec2:
         return "-".join(self._idlist)
 
 
-def get_direct_param_fixture_func(request: FixtureRequest) -> Any:
-    return request.param
-
-
 # Used for storing pseudo fixturedefs for direct parametrization.
 name2pseudofixturedef_key = StashKey[Dict[str, FixtureDef[Any]]]()
 
@@ -1387,16 +1383,8 @@ class Metafunc:
             if name2pseudofixturedef is not None and argname in name2pseudofixturedef:
                 fixturedef = name2pseudofixturedef[argname]
             else:
-                fixturedef = FixtureDef(
+                fixturedef = IdentityFixture(
-                    fixturemanager=self.definition.session._fixturemanager,
+                    self.definition.session._fixturemanager, argname, scope_
-                    baseid="",
-                    argname=argname,
-                    func=get_direct_param_fixture_func,
-                    scope=scope_,
-                    params=None,
-                    unittest=False,
-                    ids=None,
-                    _ispytest=True,
                 )
                 if name2pseudofixturedef is not None:
                     name2pseudofixturedef[argname] = fixturedef