Add unit test, don't re-raise as ValueError

astropy/modeling/core.py

@@ -1061,14 +1061,7 @@ def _validate_input_shapes(self, inputs, argnames, model_set_axis):
                 )
             )
 
-        try:
-            input_shape = check_broadcast(*all_shapes)
-        except IncompatibleShapeError as err:
-            raise ValueError(
-                "All inputs must have identical shapes or must be scalars."
-            ) from err
-
-        return input_shape
+        return check_broadcast(*all_shapes)
 
     def input_shape(self, inputs):
         """Get input shape for bounding_box evaluation."""

astropy/modeling/tests/test_models.py

@@ -29,7 +29,7 @@
 )
 from astropy.modeling.separable import separability_matrix
 from astropy.tests.helper import assert_quantity_allclose
-from astropy.utils import NumpyRNGContext, minversion
+from astropy.utils import IncompatibleShapeError, NumpyRNGContext, minversion
 from astropy.utils.compat.optional_deps import HAS_SCIPY
 
 from .example_models import models_1D, models_2D
@@ -120,6 +120,12 @@ def test_inconsistent_input_shapes():
     y.shape = (1, 10)
     result = g(x, y)
     assert result.shape == (10, 10)
+    # incompatible shapes do _not_ work
+    g = Gaussian2D()
+    x = np.arange(-1.0, 1, 0.2)
+    y = np.arange(-1.0, 1, 0.1)
+    with pytest.raises(IncompatibleShapeError):
+        g(x, y)
 
 
 def test_custom_model_bounding_box():