get inner object from object array to test arbitrary dtype

src/numpydantic/interface/dask.py

@@ -8,6 +8,7 @@ import numpy as np
 from pydantic import SerializationInfo
 
 from numpydantic.interface.interface import Interface
+from numpydantic.types import DtypeType, NDArrayType
 
 try:
     from dask.array.core import Array as DaskArray
@@ -30,6 +31,10 @@ class DaskInterface(Interface):
         """
         return DaskArray is not None and isinstance(array, DaskArray)
 
+    def get_object_dtype(self, array: NDArrayType) -> DtypeType:
+        """Dask arrays require a compute() call to retrieve a single value"""
+        return type(array.ravel()[0].compute())
+
     @classmethod
     def enabled(cls) -> bool:
         """check if we successfully imported dask"""

src/numpydantic/interface/interface.py

@@ -101,7 +101,17 @@ class Interface(ABC, Generic[T]):
         """
         Get the dtype from the input array
         """
-        return array.dtype
+        if hasattr(array.dtype, "type") and array.dtype.type is np.object_:
+            return self.get_object_dtype(array)
+        else:
+            return array.dtype
+
+    def get_object_dtype(self, array: NDArrayType) -> DtypeType:
+        """
+        When an array contains an object, get the dtype of the object contained
+        by the array.
+        """
+        return type(array.ravel()[0])
 
     def validate_dtype(self, dtype: DtypeType) -> bool:
         """

tests/conftest.py

@@ -62,6 +62,10 @@ class BasicModel(BaseModel):
     x: int
 
 
+class BadModel(BaseModel):
+    x: int
+
+
 RGB_UNION: TypeAlias = Union[
     NDArray[Shape["* x, * y"], Number],
     NDArray[Shape["* x, * y, 3 r_g_b"], Number],
@@ -137,6 +141,7 @@ def shape_cases(request) -> ValidationCase:
         ValidationCase(annotation=STRING, dtype=int, passes=False),
         ValidationCase(annotation=STRING, dtype=float, passes=False),
         ValidationCase(annotation=MODEL, dtype=BasicModel, passes=True),
+        ValidationCase(annotation=MODEL, dtype=BadModel, passes=False),
         ValidationCase(annotation=MODEL, dtype=int, passes=False),
     ],
     ids=[
@@ -162,6 +167,7 @@ def shape_cases(request) -> ValidationCase:
         "str-int",
         "str-float",
         "model-model",
+        "model-badmodel",
         "model-int",
     ],
 )