BUG: use EA.astype in ExtensionBlock.to_native_types

pandas/core/internals/blocks.py

@@ -687,7 +687,6 @@ def _try_coerce_args(self, other):
 
     def to_native_types(self, slicer=None, na_rep="nan", quoting=None, **kwargs):
         """ convert to our native types format, slicing if desired """
-
         values = self.get_values()
 
         if slicer is not None:
@@ -1783,6 +1782,21 @@ def get_values(self, dtype=None):
     def to_dense(self):
         return np.asarray(self.values)
 
+    def to_native_types(self, slicer=None, na_rep="nan", quoting=None, **kwargs):
+        """override to use ExtensionArray astype for the conversion"""
+        try:
+            values = self.values
+            if slicer is not None:
+                values = values[slicer]
+            mask = isna(values)
+            values = values.astype(str)
+            values[mask] = na_rep
+            # we are expected to return a 2-d ndarray
+            return values.reshape(1, len(values))
+        except Exception:
+            # eg SparseArray does not support setitem, needs to be converted to ndarray
+            return super().to_native_types(slicer, na_rep, quoting, **kwargs)
+
     def take_nd(self, indexer, axis=0, new_mgr_locs=None, fill_tuple=None):
         """
         Take values according to indexer and return them as a block.