Add support for __spec__

mypy/nodes.py

@@ -115,6 +115,7 @@ def set_line(
     "__file__": "__builtins__.str",
     "__package__": "__builtins__.str",
     "__annotations__": None,  # dict[str, Any] bounded in add_implicit_module_attrs()
+    "__spec__": None,  # importlib.machinery.ModuleSpec bounded in add_implicit_module_attrs()
 }
 
 

mypy/semanal.py

@@ -270,6 +270,7 @@
     TypeVarLikeType,
     TypeVarType,
     UnboundType,
+    UnionType,
     UnpackType,
     get_proper_type,
     get_proper_types,
@@ -644,6 +645,19 @@ def add_implicit_module_attrs(self, file_node: MypyFile) -> None:
                     self.defer()
                     return
                 typ = inst
+            elif name == "__spec__":
+                inst: Type | None = self.named_type_or_none("importlib.machinery.ModuleSpec")
+                if inst is None:
+                    if self.final_iteration:
+                        inst = self.named_type_or_none("builtins.object")
+                        assert inst is not None, "Cannot find builtins.object"
+                    else:
+                        self.defer()
+                        return
+                if file_node.name == "__main__":
+                    # https://docs.python.org/3/reference/import.html#main-spec
+                    inst = UnionType.make_union([inst, NoneType()])
+                typ = inst
             else:
                 assert t is not None, f"type should be specified for {name}"
                 typ = UnboundType(t)

test-data/unit/check-basic.test

@@ -219,6 +219,14 @@ reveal_type(__doc__)          # N: Revealed type is "builtins.str"
 reveal_type(__file__)         # N: Revealed type is "builtins.str"
 reveal_type(__package__)      # N: Revealed type is "builtins.str"
 reveal_type(__annotations__)  # N: Revealed type is "builtins.dict[builtins.str, Any]"
+# This will actually reveal Union[importlib.machinery.ModuleSpec, None]
+reveal_type(__spec__)         # N: Revealed type is "Union[builtins.object, None]"
+
+import module
+reveal_type(module.__name__)  # N: Revealed type is "builtins.str"
+# This will actually reveal importlib.machinery.ModuleSpec
+reveal_type(module.__spec__)  # N: Revealed type is "builtins.object"
+[file module.py]
 [builtins fixtures/primitives.pyi]