make_class(): Add "__annotations_" to generated class (#1285)

* make_class(): Add "__annotations_" to generated class

Fixes: #1271

* Fix PR#

* Flip

---------

Co-authored-by: Hynek Schlawack <hs@ox.cx>

changelog.d/1285.change.md

@@ -0,0 +1 @@
+`attrs.make_class()` now populates the `__annotations__` dict of the generated class, so that `attrs.resolve_types()` can resolve them.

src/attr/_make.py

@@ -3056,7 +3056,12 @@ def make_class(
         True,
     )
 
-    return _attrs(these=cls_dict, **attributes_arguments)(type_)
+    cls = _attrs(these=cls_dict, **attributes_arguments)(type_)
+    # Only add type annotations now or "_attrs()" will complain:
+    cls.__annotations__ = {
+        k: v.type for k, v in cls_dict.items() if v.type is not None
+    }
+    return cls
 
 
 # These are required by within this module so we define them here and merely

tests/test_make.py

@@ -1164,6 +1164,34 @@ class TestMakeClass:
 
         attr.make_class("test", {"id": attr.ib(type=str)}, (MyParent[int],))
 
+    def test_annotations(self):
+        """
+        make_class fills the __annotations__ dict for attributes with a known
+        type.
+        """
+        a = attr.ib(type=bool)
+        b = attr.ib(
+            type=None
+        )  # Won't be added to ann. b/c of unfavorable default
+        c = attr.ib()
+
+        C = attr.make_class("C", {"a": a, "b": b, "c": c})
+        C = attr.resolve_types(C)
+
+        assert {"a": bool} == C.__annotations__
+
+    def test_annotations_resolve(self):
+        """
+        resolve_types() resolves the annotations added by make_class().
+        """
+        a = attr.ib(type="bool")
+
+        C = attr.make_class("C", {"a": a})
+        C = attr.resolve_types(C)
+
+        assert attr.fields(C).a.type is bool
+        assert {"a": "bool"} == C.__annotations__
+
 
 class TestFields:
     """