push reset_index to _set_grouper

Author: aram-cedarwood

pandas/core/groupby/grouper.py

@@ -34,6 +34,7 @@
 from pandas.core.indexes.api import (
     Index,
     MultiIndex,
+    RangeIndex,
     default_index,
 )
 from pandas.core.series import Series
@@ -349,6 +350,10 @@ def _set_grouper(
                     unsorted_ax = self._grouper.take(reverse_indexer)
                     ax = unsorted_ax.take(obj.index)
                 else:
+                    if not isinstance(obj.index, RangeIndex):
+                        # GH 59350: Index is ignored when using the on keyword argument
+                        # to resample.
+                        obj = obj.reset_index(drop=True)
                     ax = self._grouper.take(obj.index)
             else:
                 if key not in obj._info_axis:

pandas/core/resample.py

@@ -1597,9 +1597,6 @@ def _gotitem(self, key, ndim, subset=None):
             if isinstance(key, list) and self.key not in key and self.key is not None:
                 key.append(self.key)
             groupby = self._groupby[key]
-            # GH 59350: Index is ignored when using the on keyword argument to resample
-            if self.key is not None:
-                groupby.obj = groupby.obj.reset_index(drop=True)
         except IndexError:
             groupby = self._groupby