BUG/API: Index.append with mixed object/Categorical indices

Author: jorisvandenbossche

pandas/indexes/base.py

@@ -1466,11 +1466,6 @@ def append(self, other):
 
         typs = _concat.get_dtype_kinds(to_concat)
 
-        if 'category' in typs:
-            # if any of the to_concat is category
-            from pandas.indexes.category import CategoricalIndex
-            return CategoricalIndex._append_same_dtype(self, to_concat, name)
-
         if len(typs) == 1:
             return self._append_same_dtype(to_concat, name=name)
         return _concat._concat_index_asobject(to_concat, name=name)

pandas/tests/indexes/test_category.py

@@ -272,11 +272,17 @@ def test_append(self):
 
         # with objects
         result = ci.append(Index(['c', 'a']))
-        expected = CategoricalIndex(list('aabbcaca'), categories=categories)
+        #expected = CategoricalIndex(list('aabbcaca'), categories=categories)
+        expected = Index(list('aabbcaca'))
         tm.assert_index_equal(result, expected, exact=True)
 
         # invalid objects
-        self.assertRaises(TypeError, lambda: ci.append(Index(['a', 'd'])))
+        #self.assertRaises(TypeError, lambda: ci.append(Index(['a', 'd'])))
+
+        # GH14298 - if base object is not categorical -> coerce to object
+        result = Index(['c', 'a']).append(ci)
+        expected = Index(list('caaabbca'))
+        tm.assert_index_equal(result, expected, exact=True)
 
     def test_insert(self):