Add NotImplementedError when on is specified in DataFrame.join. (NVID…

…IA#11275)

Resolves NVIDIA#8364

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: rapidsai/cudf#11275

python/cudf/cudf/core/dataframe.py

@@ -3807,6 +3807,8 @@ def join(
         - *other* must be a single DataFrame for now.
         - *on* is not supported yet due to lack of multi-index support.
         """
+        if on is not None:
+            raise NotImplementedError("The on parameter is not yet supported")
 
         df = self.merge(
             other,

python/cudf/cudf/tests/test_joining.py

@@ -2181,3 +2181,10 @@ def test_join_multiindex_index():
     expect = lhs.to_pandas().join(rhs.to_pandas(), how="inner")
     got = lhs.join(rhs, how="inner")
     assert_join_results_equal(expect, got, how="inner")
+
+
+def test_dataframe_join_on():
+    """Verify that specifying the on parameter gives a NotImplementedError."""
+    df = cudf.DataFrame({"a": [1, 2, 3]})
+    with pytest.raises(NotImplementedError):
+        df.join(df, on="a")