fixtures: a few more cleanups

src/_pytest/fixtures.py

@@ -388,6 +388,14 @@ def scope(self) -> _ScopeName:
         """Scope string, one of "function", "class", "module", "package", "session"."""
         return self._scope.value
 
+    @abc.abstractmethod
+    def _check_scope(
+        self,
+        requested_fixturedef: Union["FixtureDef[object]", PseudoFixtureDef[object]],
+        requested_scope: Scope,
+    ) -> None:
+        raise NotImplementedError()
+
     @property
     def fixturenames(self) -> List[str]:
         """Names of all active fixtures in this request."""
@@ -565,6 +573,8 @@ def _get_active_fixturedef(
                 raise
             self._compute_fixture_value(fixturedef)
             self._fixture_defs[argname] = fixturedef
+        else:
+            self._check_scope(fixturedef, fixturedef._scope)
         return fixturedef
 
     def _get_fixturestack(self) -> List["FixtureDef[Any]"]:
@@ -632,12 +642,12 @@ def _compute_fixture_value(self, fixturedef: "FixtureDef[object]") -> None:
                 )
                 fail(msg, pytrace=False)
 
+        # Check if a higher-level scoped fixture accesses a lower level one.
+        self._check_scope(fixturedef, scope)
+
         subrequest = SubRequest(
             self, scope, param, param_index, fixturedef, _ispytest=True
         )
-
-        # Check if a higher-level scoped fixture accesses a lower level one.
-        subrequest._check_scope(argname, self._scope, scope)
         try:
             # Call the fixture function.
             fixturedef.execute(request=subrequest)
@@ -669,6 +679,14 @@ def __init__(self, pyfuncitem: "Function", *, _ispytest: bool = False) -> None:
     def _scope(self) -> Scope:
         return Scope.Function
 
+    def _check_scope(
+        self,
+        requested_fixturedef: Union["FixtureDef[object]", PseudoFixtureDef[object]],
+        requested_scope: Scope,
+    ) -> None:
+        # TopRequest always has function scope so always valid.
+        pass
+
     @property
     def node(self):
         return self._pyfuncitem
@@ -740,37 +758,34 @@ def node(self):
 
     def _check_scope(
         self,
-        argname: str,
-        invoking_scope: Scope,
+        requested_fixturedef: Union["FixtureDef[object]", PseudoFixtureDef[object]],
         requested_scope: Scope,
     ) -> None:
-        if argname == "request":
+        if isinstance(requested_fixturedef, PseudoFixtureDef):
             return
-        if invoking_scope > requested_scope:
+        if self._scope > requested_scope:
             # Try to report something helpful.
-            text = "\n".join(self._factorytraceback())
+            argname = requested_fixturedef.argname
+            fixture_stack = "\n".join(
+                self._format_fixturedef_line(fixturedef)
+                for fixturedef in self._get_fixturestack()
+            )
+            requested_fixture = self._format_fixturedef_line(requested_fixturedef)
             fail(
                 f"ScopeMismatch: You tried to access the {requested_scope.value} scoped "
-                f"fixture {argname} with a {invoking_scope.value} scoped request object, "
-                f"involved factories:\n{text}",
+                f"fixture {argname} with a {self._scope.value} scoped request object. "
+                f"Requesting fixture stack:\n{fixture_stack}\n"
+                f"Requested fixture:\n{requested_fixture}",
                 pytrace=False,
             )
 
-    def _factorytraceback(self) -> List[str]:
-        lines = []
-        for fixturedef in self._get_fixturestack():
-            factory = fixturedef.func
-            fs, lineno = getfslineno(factory)
-            if isinstance(fs, Path):
-                session: Session = self._pyfuncitem.session
-                p = bestrelpath(session.path, fs)
-            else:
-                p = fs
-            lines.append(
-                "%s:%d:  def %s%s"
-                % (p, lineno + 1, factory.__name__, inspect.signature(factory))
-            )
-        return lines
+    def _format_fixturedef_line(self, fixturedef: "FixtureDef[object]") -> str:
+        factory = fixturedef.func
+        path, lineno = getfslineno(factory)
+        if isinstance(path, Path):
+            path = bestrelpath(self._pyfuncitem.session.path, path)
+        signature = inspect.signature(factory)
+        return f"{path}:{lineno + 1}:  def {factory.__name__}{signature}"
 
     def addfinalizer(self, finalizer: Callable[[], object]) -> None:
         self._fixturedef.addfinalizer(finalizer)
@@ -1046,9 +1061,7 @@ def execute(self, request: SubRequest) -> FixtureValue:
         # with their finalization.
         for argname in self.argnames:
             fixturedef = request._get_active_fixturedef(argname)
-            if argname != "request":
-                # PseudoFixtureDef is only for "request".
-                assert isinstance(fixturedef, FixtureDef)
+            if not isinstance(fixturedef, PseudoFixtureDef):
                 fixturedef.addfinalizer(functools.partial(self.finish, request=request))
 
         my_cache_key = self.cache_key(request)
@@ -1108,11 +1121,7 @@ def pytest_fixture_setup(
     """Execution of fixture setup."""
     kwargs = {}
     for argname in fixturedef.argnames:
-        fixdef = request._get_active_fixturedef(argname)
-        assert fixdef.cached_result is not None
-        result, arg_cache_key, exc = fixdef.cached_result
-        request._check_scope(argname, request._scope, fixdef._scope)
-        kwargs[argname] = result
+        kwargs[argname] = request.getfixturevalue(argname)
 
     fixturefunc = resolve_fixture_function(fixturedef, request)
     my_cache_key = fixturedef.cache_key(request)

testing/python/fixtures.py

@@ -1247,8 +1247,9 @@ def test_add(arg2):
         result = pytester.runpytest()
         result.stdout.fnmatch_lines(
             [
-                "*ScopeMismatch*involved factories*",
+                "*ScopeMismatch*Requesting fixture stack*",
                 "test_receives_funcargs_scope_mismatch.py:6:  def arg2(arg1)",
+                "Requested fixture:",
                 "test_receives_funcargs_scope_mismatch.py:2:  def arg1()",
                 "*1 error*",
             ]
@@ -1274,7 +1275,13 @@ def test_add(arg1, arg2):
         )
         result = pytester.runpytest()
         result.stdout.fnmatch_lines(
-            ["*ScopeMismatch*involved factories*", "* def arg2*", "*1 error*"]
+            [
+                "*ScopeMismatch*Requesting fixture stack*",
+                "* def arg2(arg1)",
+                "Requested fixture:",
+                "* def arg1()",
+                "*1 error*",
+            ],
         )
 
     def test_invalid_scope(self, pytester: Pytester) -> None:
@@ -2488,8 +2495,10 @@ def test_it(request, fixfunc):
         assert result.ret == ExitCode.TESTS_FAILED
         result.stdout.fnmatch_lines(
             [
-                "*ScopeMismatch*involved factories*",
+                "*ScopeMismatch*Requesting fixture stack*",
                 "test_it.py:6:  def fixmod(fixfunc)",
+                "Requested fixture:",
+                "test_it.py:3:  def fixfunc()",
             ]
         )