check: annotated dtypes match those specified in Field.dtype

src/patito/pydantic.py

@@ -220,6 +220,8 @@ def _valid_dtypes(  # noqa: C901
             return [pl.List(dtype) for dtype in item_dtypes]
 
         if "dtype" in props and 'anyOf' not in props:
+            if props['dtype'] not in cls._pydantic_type_to_valid_polars_types(props):  # TODO should we allow pl floats for integer columns? Other type hierarchies to consider?
+                raise ValueError(f"Invalid dtype {props['dtype']} for column '{column}'. Check that specified dtype is allowable for the given type annotations.")
             return [
                 props["dtype"],
             ]
@@ -237,7 +239,12 @@ def _valid_dtypes(  # noqa: C901
                     column, {"type": PYTHON_TO_PYDANTIC_TYPES.get(type(props["const"]))}
                 )
             return None
-        elif props["type"] == "integer":
+
+        return cls._pydantic_type_to_valid_polars_types(props)
+
+    @staticmethod
+    def _pydantic_type_to_valid_polars_types(props: Dict) -> Optional[List[pl.DataType]]:
+        if props["type"] == "integer":
             return [
                 pl.Int64,
                 pl.Int32,
@@ -272,8 +279,6 @@ def _valid_dtypes(  # noqa: C901
                 return None  # pragma: no cover
         elif props["type"] == "null":
             return [pl.Null]
-        else:  # pragma: no cover
-            return None
 
     @property
     def valid_sql_types(  # type: ignore  # noqa: C901

tests/test_model.py

@@ -462,3 +462,22 @@ class Test(pt.Model):
 
     assert Test.nullable_columns == {"foo"}
     assert set(Test.valid_dtypes['foo']) == {pl.Utf8, pl.Null}
+
+
+def test_conflicting_type_dtype():
+
+    class Test(pt.Model):
+        foo: int = pt.Field(dtype=pl.Utf8)
+
+    with pytest.raises(ValueError):
+        Test.valid_dtypes()
+
+    class Test(pt.Model):
+        foo: str = pt.Field(dtype=pl.Float32)
+
+    with pytest.raises(ValueError):
+        Test.valid_dtypes()
+
+
+if __name__ == "__main__":
+    test_conflicting_type_dtype()