fix(annots): do not erase __annotations__ classvar (#25)

koerce/annots.py

@@ -666,7 +666,7 @@ def __new__(
         slots: list[str] = list(dct.pop("__slots__", []))
         module: str | None = dct.pop("__module__", None)
         qualname: str = dct.pop("__qualname__", clsname)
-        annotations: dict[str, Any] = dct.pop("__annotations__", {})
+        annotations: dict[str, Any] = dct.get("__annotations__", {})
         if module is None:
             self_qualname = None
         else:

koerce/tests/test_annots.py

@@ -1118,6 +1118,14 @@ class Between(BetweenSimple):
     # assert obj.copy(lower=8) == obj2
 
 
+def test_annotable_keeps_annotations_classvar():
+    class MyClass(Annotable):
+        a: int
+        b: str
+
+    assert MyClass.__annotations__ == {"a": "int", "b": "str"}
+
+
 def test_annotable_with_bound_typevars_properly_coerce_values():
     v = MyValue(1.1, 2.2, 3.3)
     assert isinstance(v.integer, MyInt)

koerce/tests/test_utils.py

@@ -128,7 +128,7 @@ def test_get_type_boundvars() -> None:
 
 
 def test_get_type_boundvars_unable_to_deduce() -> None:
-    msg = "Unable to deduce corresponding type attributes..."
+    msg = "Unable to deduce corresponding attributes..."
     with pytest.raises(ValueError, match=msg):
         get_type_boundvars(MyDict[int, str])
 

koerce/utils.py

@@ -165,7 +165,9 @@ def get_type_boundvars(typ: Any) -> dict[TypeVar, tuple[str, type]]:
 
     if params:
         raise ValueError(
-            f"Unable to deduce corresponding type attributes for the following type variables: {params}"
+            f"Unable to deduce corresponding attributes for type parameters of {typ}.\n"
+            f"Missing attributes with typehints for the following type variables: {params}.\n"
+            f"Available type hints: {hints}"
         )
 
     return result