Fix crashed related to forward references in attrs classes

This is similar to #12762, but for attrs classes.

Author: JukkaL

mypy/plugins/attrs.py

@@ -260,7 +260,7 @@ def _get_decorator_optional_bool_argument(
 
 def attr_class_maker_callback(ctx: 'mypy.plugin.ClassDefContext',
                               auto_attribs_default: Optional[bool] = False,
-                              frozen_default: bool = False) -> None:
+                              frozen_default: bool = False) -> bool:
     """Add necessary dunder methods to classes decorated with attr.s.
 
     attrs is a package that lets you define classes without writing dull boilerplate code.
@@ -286,27 +286,24 @@ def attr_class_maker_callback(ctx: 'mypy.plugin.ClassDefContext',
     if ctx.api.options.python_version[0] < 3:
         if auto_attribs:
             ctx.api.fail("auto_attribs is not supported in Python 2", ctx.reason)
-            return
+            return True
         if not info.defn.base_type_exprs:
             # Note: This will not catch subclassing old-style classes.
             ctx.api.fail("attrs only works with new-style classes", info.defn)
-            return
+            return True
         if kw_only:
             ctx.api.fail(KW_ONLY_PYTHON_2_UNSUPPORTED, ctx.reason)
-            return
+            return True
 
     attributes = _analyze_class(ctx, auto_attribs, kw_only)
 
     # Check if attribute types are ready.
     for attr in attributes:
         node = info.get(attr.name)
-        if node is None:
-            # This name is likely blocked by a star import. We don't need to defer because
-            # defer() is already called by mark_incomplete().
-            return
-        if node.type is None and not ctx.api.final_iteration:
-            ctx.api.defer()
-            return
+        if node is None or node.type is None:
+            # This name is likely blocked by some semantic analysis error that
+            # should have been reported already.
+            return True
 
     _add_attrs_magic_attribute(ctx, [(attr.name, info[attr.name].type) for attr in attributes])
     if slots:
@@ -330,6 +327,8 @@ def attr_class_maker_callback(ctx: 'mypy.plugin.ClassDefContext',
     if frozen:
         _make_frozen(ctx, attributes)
 
+    return True
+
 
 def _get_frozen(ctx: 'mypy.plugin.ClassDefContext', frozen_default: bool) -> bool:
     """Return whether this class is frozen."""

mypy/plugins/default.py

@@ -94,10 +94,24 @@ def get_attribute_hook(self, fullname: str
 
     def get_class_decorator_hook(self, fullname: str
                                  ) -> Optional[Callable[[ClassDefContext], None]]:
-        from mypy.plugins import attrs
         from mypy.plugins import dataclasses
 
-        if fullname in attrs.attr_class_makers:
+        if fullname in dataclasses.dataclass_makers:
+            return dataclasses.dataclass_tag_callback
+
+        return None
+
+    def get_class_decorator_hook_2(self, fullname: str
+                                   ) -> Optional[Callable[[ClassDefContext], bool]]:
+        from mypy.plugins import dataclasses
+        from mypy.plugins import functools
+        from mypy.plugins import attrs
+
+        if fullname in dataclasses.dataclass_makers:
+            return dataclasses.dataclass_class_maker_callback
+        elif fullname in functools.functools_total_ordering_makers:
+            return functools.functools_total_ordering_maker_callback
+        elif fullname in attrs.attr_class_makers:
             return attrs.attr_class_maker_callback
         elif fullname in attrs.attr_dataclass_makers:
             return partial(
@@ -115,20 +129,6 @@ def get_class_decorator_hook(self, fullname: str
                 attrs.attr_class_maker_callback,
                 auto_attribs_default=None,
             )
-        elif fullname in dataclasses.dataclass_makers:
-            return dataclasses.dataclass_tag_callback
-
-        return None
-
-    def get_class_decorator_hook_2(self, fullname: str
-                                   ) -> Optional[Callable[[ClassDefContext], bool]]:
-        from mypy.plugins import dataclasses
-        from mypy.plugins import functools
-
-        if fullname in dataclasses.dataclass_makers:
-            return dataclasses.dataclass_class_maker_callback
-        elif fullname in functools.functools_total_ordering_makers:
-            return functools.functools_total_ordering_maker_callback
 
         return None
 

test-data/unit/check-attr.test

@@ -1591,3 +1591,17 @@ class B:
 class AB(A, B):
     pass
 [builtins fixtures/attr.pyi]
+
+[case testAttrsForwardReferenceInTypeVarBound]
+from typing import TypeVar, Generic
+import attr
+
+T = TypeVar("T", bound="C")
+
+@attr.define
+class D(Generic[T]):
+    x: int
+
+class C:
+    pass
+[builtins fixtures/attr.pyi]