Fix crash on Any metaclass in incremental mode (#14495)

Fixes #14254

This essentially re-implements #13605
in a simpler way that also works in incremental mode. Also I decided to
set `meta_fallback_to_any` in case of errors, to match how we do this
for base classes.

Author: ilevkivskyi

mypy/checkmember.py

@@ -901,7 +901,7 @@ def analyze_class_attribute_access(
             # For modules use direct symbol table lookup.
             if not itype.extra_attrs.mod_name:
                 return itype.extra_attrs.attrs[name]
-        if info.fallback_to_any:
+        if info.fallback_to_any or info.meta_fallback_to_any:
             return apply_class_attr_hook(mx, hook, AnyType(TypeOfAny.special_form))
         return None
 

mypy/nodes.py

@@ -2800,6 +2800,7 @@ class is generic then it will be a type constructor of higher kind.
         "inferring",
         "is_enum",
         "fallback_to_any",
+        "meta_fallback_to_any",
         "type_vars",
         "has_param_spec_type",
         "bases",
@@ -2894,6 +2895,10 @@ class is generic then it will be a type constructor of higher kind.
     # (and __setattr__), but without the __getattr__ method.
     fallback_to_any: bool
 
+    # Same as above but for cases where metaclass has type Any. This will suppress
+    # all attribute errors only for *class object* access.
+    meta_fallback_to_any: bool
+
     # Information related to type annotations.
 
     # Generic type variable names (full names)
@@ -2963,6 +2968,7 @@ class is generic then it will be a type constructor of higher kind.
         "is_abstract",
         "is_enum",
         "fallback_to_any",
+        "meta_fallback_to_any",
         "is_named_tuple",
         "is_newtype",
         "is_protocol",
@@ -3002,6 +3008,7 @@ def __init__(self, names: SymbolTable, defn: ClassDef, module_name: str) -> None
         self.is_final = False
         self.is_enum = False
         self.fallback_to_any = False
+        self.meta_fallback_to_any = False
         self._promote = []
         self.alt_promote = None
         self.tuple_type = None

mypy/semanal.py

@@ -1579,7 +1579,9 @@ def analyze_class(self, defn: ClassDef) -> None:
             self.mark_incomplete(defn.name, defn)
             return
 
-        declared_metaclass, should_defer = self.get_declared_metaclass(defn.name, defn.metaclass)
+        declared_metaclass, should_defer, any_meta = self.get_declared_metaclass(
+            defn.name, defn.metaclass
+        )
         if should_defer or self.found_incomplete_ref(tag):
             # Metaclass was not ready. Defer current target.
             self.mark_incomplete(defn.name, defn)
@@ -1599,6 +1601,8 @@ def analyze_class(self, defn: ClassDef) -> None:
         self.setup_type_vars(defn, tvar_defs)
         if base_error:
             defn.info.fallback_to_any = True
+        if any_meta:
+            defn.info.meta_fallback_to_any = True
 
         with self.scope.class_scope(defn.info):
             self.configure_base_classes(defn, base_types)
@@ -2247,8 +2251,17 @@ def is_base_class(self, t: TypeInfo, s: TypeInfo) -> bool:
 
     def get_declared_metaclass(
         self, name: str, metaclass_expr: Expression | None
-    ) -> tuple[Instance | None, bool]:
-        """Returns either metaclass instance or boolean whether we should defer."""
+    ) -> tuple[Instance | None, bool, bool]:
+        """Get declared metaclass from metaclass expression.
+
+        Returns a tuple of three values:
+          * A metaclass instance or None
+          * A boolean indicating whether we should defer
+          * A boolean indicating whether we should set metaclass Any fallback
+            (either for Any metaclass or invalid/dynamic metaclass).
+
+        The two boolean flags can only be True if instance is None.
+        """
         declared_metaclass = None
         if metaclass_expr:
             metaclass_name = None
@@ -2258,25 +2271,20 @@ def get_declared_metaclass(
                 metaclass_name = get_member_expr_fullname(metaclass_expr)
             if metaclass_name is None:
                 self.fail(f'Dynamic metaclass not supported for "{name}"', metaclass_expr)
-                return None, False
+                return None, False, True
             sym = self.lookup_qualified(metaclass_name, metaclass_expr)
             if sym is None:
                 # Probably a name error - it is already handled elsewhere
-                return None, False
+                return None, False, True
             if isinstance(sym.node, Var) and isinstance(get_proper_type(sym.node.type), AnyType):
-                # Create a fake TypeInfo that fallbacks to `Any`, basically allowing
-                # all the attributes. Same thing as we do for `Any` base class.
-                any_info = self.make_empty_type_info(ClassDef(sym.node.name, Block([])))
-                any_info.fallback_to_any = True
-                any_info._fullname = sym.node.fullname
                 if self.options.disallow_subclassing_any:
                     self.fail(
-                        f'Class cannot use "{any_info.fullname}" as a metaclass (has type "Any")',
+                        f'Class cannot use "{sym.node.name}" as a metaclass (has type "Any")',
                         metaclass_expr,
                     )
-                return Instance(any_info, []), False
+                return None, False, True
             if isinstance(sym.node, PlaceholderNode):
-                return None, True  # defer later in the caller
+                return None, True, False  # defer later in the caller
 
             # Support type aliases, like `_Meta: TypeAlias = type`
             if (
@@ -2291,16 +2299,16 @@ def get_declared_metaclass(
 
             if not isinstance(metaclass_info, TypeInfo) or metaclass_info.tuple_type is not None:
                 self.fail(f'Invalid metaclass "{metaclass_name}"', metaclass_expr)
-                return None, False
+                return None, False, False
             if not metaclass_info.is_metaclass():
                 self.fail(
                     'Metaclasses not inheriting from "type" are not supported', metaclass_expr
                 )
-                return None, False
+                return None, False, False
             inst = fill_typevars(metaclass_info)
             assert isinstance(inst, Instance)
             declared_metaclass = inst
-        return declared_metaclass, False
+        return declared_metaclass, False, False
 
     def recalculate_metaclass(self, defn: ClassDef, declared_metaclass: Instance | None) -> None:
         defn.info.declared_metaclass = declared_metaclass

mypy/server/astdiff.py

@@ -255,6 +255,7 @@ def snapshot_definition(node: SymbolNode | None, common: tuple[object, ...]) ->
             node.is_enum,
             node.is_protocol,
             node.fallback_to_any,
+            node.meta_fallback_to_any,
             node.is_named_tuple,
             node.is_newtype,
             # We need this to e.g. trigger metaclass calculation in subclasses.

mypy/subtypes.py

@@ -1167,7 +1167,7 @@ def find_member(
                     if isinstance(getattr_type, CallableType):
                         return getattr_type.ret_type
                     return getattr_type
-        if itype.type.fallback_to_any:
+        if itype.type.fallback_to_any or class_obj and itype.type.meta_fallback_to_any:
             return AnyType(TypeOfAny.special_form)
         if isinstance(v, TypeInfo):
             # PEP 544 doesn't specify anything about such use cases. So we just try

test-data/unit/check-classes.test

@@ -4439,7 +4439,7 @@ def f(TB: Type[B]):
     reveal_type(TB.x)  # N: Revealed type is "builtins.int"
 
 [case testMetaclassAsAny]
-from typing import Any, ClassVar
+from typing import Any, ClassVar, Type
 
 MyAny: Any
 class WithMeta(metaclass=MyAny):
@@ -4451,13 +4451,15 @@ reveal_type(WithMeta.x)   # N: Revealed type is "builtins.int"
 reveal_type(WithMeta().x) # N: Revealed type is "builtins.int"
 WithMeta().m              # E: "WithMeta" has no attribute "m"
 WithMeta().a              # E: "WithMeta" has no attribute "a"
+t: Type[WithMeta]
+t.unknown  # OK
 
 [case testMetaclassAsAnyWithAFlag]
 # flags: --disallow-subclassing-any
-from typing import Any, ClassVar
+from typing import Any, ClassVar, Type
 
 MyAny: Any
-class WithMeta(metaclass=MyAny):  # E: Class cannot use "__main__.MyAny" as a metaclass (has type "Any")
+class WithMeta(metaclass=MyAny):  # E: Class cannot use "MyAny" as a metaclass (has type "Any")
     x: ClassVar[int]
 
 reveal_type(WithMeta.a)   # N: Revealed type is "Any"
@@ -4466,6 +4468,8 @@ reveal_type(WithMeta.x)   # N: Revealed type is "builtins.int"
 reveal_type(WithMeta().x) # N: Revealed type is "builtins.int"
 WithMeta().m              # E: "WithMeta" has no attribute "m"
 WithMeta().a              # E: "WithMeta" has no attribute "a"
+t: Type[WithMeta]
+t.unknown  # OK
 
 [case testMetaclassIterable]
 from typing import Iterable, Iterator

test-data/unit/check-incremental.test

@@ -6348,3 +6348,14 @@ class C(B):
         self.x = self.foo()
 [out]
 [out2]
+
+[case testNoCrashIncrementalMetaAny]
+import a
+[file a.py]
+from m import Foo
+[file a.py.2]
+from m import Foo
+# touch
+[file m.py]
+from missing_module import Meta  # type: ignore[import]
+class Foo(metaclass=Meta): ...

test-data/unit/fine-grained.test

@@ -3124,7 +3124,6 @@ whatever: int
 [out]
 ==
 b.py:2: error: Name "c.M" is not defined
-a.py:3: error: "Type[B]" has no attribute "x"
 
 [case testFixMissingMetaclass]
 import a
@@ -3143,7 +3142,6 @@ class M(type):
     x: int
 [out]
 b.py:2: error: Name "c.M" is not defined
-a.py:3: error: "Type[B]" has no attribute "x"
 ==
 
 [case testGoodMetaclassSpoiled]