resolve

src/psygnal/_group_descriptor.py

@@ -2,6 +2,7 @@
 
 import contextlib
 import copy
+import inspect
 import operator
 import sys
 import warnings
@@ -13,6 +14,7 @@
     Any,
     Callable,
     ClassVar,
+    ForwardRef,
     Iterable,
     Literal,
     Mapping,
@@ -587,10 +589,19 @@ def __set_name__(self, owner: type, name: str) -> None:
     def _find_validators(self, owner: type) -> dict[str, list[Validator]]:
         validators: dict[str, list[Validator]] = {}
         for field, annotation in owner.__annotations__.items():
-            if get_origin(annotation) is Annotated:
-                for item in get_args(annotation)[1:]:
-                    if isinstance(item, Validator):
-                        validators.setdefault(field, []).append(item)
+            try:
+                annotation = _resolve(annotation, owner)
+                if get_origin(annotation) is Annotated:
+                    for item in get_args(annotation)[1:]:
+                        if isinstance(item, Validator):
+                            validators.setdefault(field, []).append(item)
+            except Exception:
+                warnings.warn(
+                    f"Unable to resolve type annotation {annotation}"
+                    "Psygnal Validator will not work",
+                    stacklevel=2,
+                )
+
         return validators
 
     def _do_patch_setattr(self, owner: type, with_aliases: bool = True) -> None:
@@ -725,3 +736,13 @@ def __call__(self, value: Any, *, name: str, owner: Any) -> Any:
                 f"Error setting value {value!r} for field {name!r} "
                 f"on type {type(owner)}: {e}"
             ) from e
+
+
+def _resolve(annotation: Any, owner: Any) -> Any:
+    if isinstance(annotation, str):
+        annotation = ForwardRef(annotation)
+    if isinstance(annotation, ForwardRef):
+        guard: frozenset = frozenset()
+        _globals = inspect.getmodule(owner).__dict__
+        annotation = annotation._evaluate(_globals, {}, guard)
+    return annotation

tests/test_validator.py

@@ -6,16 +6,17 @@
 from psygnal import Validator, evented
 
 
-def test_validator():
-    def _is_positive(value: Any) -> int:
-        try:
-            _value = int(value)
-        except (ValueError, TypeError):
-            raise ValueError("Value must be an integer") from None
-        if not _value > 0:
-            raise ValueError("Value must be positive")
-        return _value
+def _is_positive(value: Any) -> int:
+    try:
+        _value = int(value)
+    except (ValueError, TypeError):
+        raise ValueError("Value must be an integer") from None
+    if not _value > 0:
+        raise ValueError("Value must be positive")
+    return _value
+
 
+def test_validator():
     @evented
     @dataclass
     class Foo:
@@ -27,3 +28,23 @@ class Foo:
     assert isinstance(foo.x, int)
     with pytest.raises(ValueError):
         foo.x = -1
+
+
+def test_validator_resolution():
+    @evented
+    @dataclass
+    class Bar:
+        x: "Annotated[int, Validator(_is_positive)]"
+
+    with pytest.raises(ValueError, match="Value must be positive"):
+        Bar(x=-1)
+
+    def _local_func(value: Any) -> Any:
+        return value
+
+    with pytest.warns(UserWarning, match="Unable to resolve type"):
+
+        @evented
+        @dataclass
+        class Baz:
+            x: "Annotated[int, Validator(_local_func)]"