Fix scalar case in XElemwise

Author: ricardoV94

pytensor/xtensor/vectorization.py

@@ -36,7 +36,10 @@ def make_node(self, *inputs):
                     # Keep the non-None shape
                     dims_and_shape[dim] = dim_length
 
-        output_dims, output_shape = zip(*dims_and_shape.items())
+        if dims_and_shape:
+            output_dims, output_shape = zip(*dims_and_shape.items())
+        else:
+            output_dims, output_shape = (), ()
 
         dummy_scalars = [ps.get_scalar_type(inp.type.dtype)() for inp in inputs]
         output_dtypes = [

tests/xtensor/test_math.py

@@ -14,6 +14,18 @@
 from tests.xtensor.util import xr_assert_allclose, xr_function
 
 
+def test_scalar_case():
+    x = xtensor("x", dims=(), shape=())
+    y = xtensor("y", dims=(), shape=())
+    out = add(x, y)
+
+    fn = function([x, y], out)
+
+    x_test = DataArray(2.0, dims=())
+    y_test = DataArray(3.0, dims=())
+    np.testing.assert_allclose(fn(x_test.values, y_test.values), 5.0)
+
+
 def test_dimension_alignment():
     x = xtensor("x", dims=("city", "country", "planet"), shape=(2, 3, 4))
     y = xtensor(