API: deprecate broadcasting TimeSeries across datetime indexed DataFr…

…ame index by default #2304

pandas/core/frame.py

@@ -3438,6 +3438,11 @@ def _combine_series_infer(self, other, func, fill_value=None):
 
         # teeny hack because one does DataFrame + TimeSeries all the time
         if self.index.is_all_dates and other.index.is_all_dates:
+            import warnings
+            warnings.warn(("TimeSeries broadcasting across DataFrame index "
+                           "by default is deprecated. Please use "
+                           "DataFrame.sub"),
+                           FutureWarning)
             return self._combine_match_index(other, func, fill_value)
         else:
             return self._combine_match_columns(other, func, fill_value)

pandas/tests/test_frame.py

@@ -3459,6 +3459,11 @@ def test_combineSeries(self):
         self.assert_(np.isnan(larger_added['E']).all())
 
         # TimeSeries
+        import sys
+
+        buf = StringIO()
+        sys.stderr = buf
+
         ts = self.tsframe['A']
         added = self.tsframe + ts
 
@@ -3474,6 +3479,8 @@ def test_combineSeries(self):
         smaller_added2 = self.tsframe + smaller_ts
         assert_frame_equal(smaller_added, smaller_added2)
 
+        sys.stderr = sys.__stderr__
+
         # length 0
         result = self.tsframe + ts[:0]