fix: fix AttributeError: 'FieldInfo' object has no attribute 'field_info' (#32)

* fix: fix issue AttributeError: 'FieldInfo' object has no attribute 'field_info' #31

* add another test

Author: tlambert03

src/fieldz/adapters/_pydantic.py

@@ -180,7 +180,8 @@ def fields(
     | type[pydantic.BaseModel]
     | type[PydanticV1BaseModel],
 ) -> tuple[Field, ...]:
-    if hasattr(type(obj), "model_fields") or hasattr(obj, "__pydantic_fields__"):
+    cls = obj if isinstance(obj, type) else type(obj)
+    if hasattr(cls, "model_fields") or hasattr(obj, "__pydantic_fields__"):
         obj = cast("pydantic.BaseModel | type[pydantic.BaseModel]", obj)
         return tuple(_fields_v2(obj))
     if hasattr(obj, "__pydantic_model__"):

tests/test_pydantic.py

@@ -22,12 +22,13 @@ class M(BaseModel):
         e: e_constr = "abc"  # type: ignore
         f: str = f_field
 
-    for f in fields(M):
-        assert f.constraints
-        if f.name in {"e", "f"}:
-            assert f.constraints.pattern == PATTERN
-        else:
-            assert f.constraints.ge == 42
-            assert f.constraints.le == 100
-            assert f.default == 50
-            assert f.default == 50
+    for obj in (M, M()):
+        for f in fields(obj):
+            assert f.constraints
+            if f.name in {"e", "f"}:
+                assert f.constraints.pattern == PATTERN
+            else:
+                assert f.constraints.ge == 42
+                assert f.constraints.le == 100
+                assert f.default == 50
+                assert f.default == 50