fix: handle tuple dtype in DataType repr and error message

dpdata/data_type.py

@@ -32,6 +32,13 @@ class DataError(Exception):
     """Data is not correct."""
 
 
+def _dtype_name(dtype) -> str:
+    """Return a readable name for a dtype that may be a type or a tuple of types."""
+    if isinstance(dtype, tuple):
+        return ", ".join(t.__name__ for t in dtype)
+    return dtype.__name__
+
+
 class DataType:
     """DataType represents a type of data, like coordinates, energies, etc.
 
@@ -96,7 +103,7 @@ def __repr__(self) -> str:
             string representation
         """
         return (
-            f"DataType(name='{self.name}', dtype={self.dtype.__name__}, "
+            f"DataType(name='{self.name}', dtype={_dtype_name(self.dtype)}, "
             f"shape={self.shape}, required={self.required}, "
             f"deepmd_name='{self.deepmd_name}')"
         )
@@ -145,7 +152,7 @@ def check(self, system: System):
                 pass
             elif not isinstance(data, self.dtype):
                 raise DataError(
-                    f"Type of {self.name} is {type(data).__name__}, but expected {self.dtype.__name__}"
+                    f"Type of {self.name} is {type(data).__name__}, but expected {_dtype_name(self.dtype)}"
                 )
             # check shape
             if self.shape is not None:

tests/test_custom_data_type.py

@@ -7,7 +7,7 @@
 import numpy as np
 
 import dpdata
-from dpdata.data_type import Axis, DataType
+from dpdata.data_type import Axis, DataError, DataType
 
 
 class TestDataType(unittest.TestCase):
@@ -41,6 +41,31 @@ def test_repr(self):
         )
         self.assertEqual(repr(dt), expected)
 
+    def test_repr_tuple_dtype(self):
+        """Regression test for #989: repr must handle a tuple dtype.
+
+        ``check`` accepts ``dtype`` as a ``type`` or a ``tuple[type]``, so repr
+        (and the type-mismatch error) must not assume ``dtype`` has ``__name__``.
+        """
+        dt = DataType("test", (list, np.ndarray), shape=(Axis.NFRAMES, 3))
+        expected = (
+            "DataType(name='test', dtype=list, ndarray, "
+            "shape=(<Axis.NFRAMES: 'nframes'>, 3), required=True, "
+            "deepmd_name='test')"
+        )
+        self.assertEqual(repr(dt), expected)
+
+    def test_check_tuple_dtype_error_message(self):
+        """Regression test for #989: a type mismatch against a tuple dtype must
+        raise a readable DataError, not AttributeError on ``tuple.__name__``.
+        """
+        dt = DataType("test", (list, np.ndarray), shape=(Axis.NFRAMES,))
+        system = dpdata.System()
+        system.data["test"] = "not a list or ndarray"
+        with self.assertRaises(DataError) as cm:
+            dt.check(system)
+        self.assertIn("expected list, ndarray", str(cm.exception))
+
     def test_register_same_data_type_no_warning(self):
         """Test registering identical DataType instances should not warn."""
         dt1 = DataType("test_same", np.ndarray, shape=(Axis.NFRAMES, 3))