BUG: Fixed SparseArray formatter

We want to fall back to the implementation in formats.

Author: TomAugspurger

pandas/core/arrays/base.py

@@ -676,7 +676,7 @@ def __repr__(self):
                                dtype=self.dtype)
 
     def _formatter(self, boxed=False):
-        # type: (bool) -> Callable[[Any], str]
+        # type: (bool) -> Callable[[Any], Optional[str]]
         """Formatting function for scalar values.
 
         This is used in the default '__repr__'. The returned formatting

pandas/core/arrays/sparse.py

@@ -1739,12 +1739,7 @@ def __unicode__(self):
             index=printing.pprint_thing(self.sp_index))
 
     def _formatter(self, boxed=False):
-        def fmt(x):
-            if isna(x) and isinstance(x, float):
-                return 'NaN'
-            return str(x)
-
-        return fmt
+        return None
 
 
 SparseArray._add_arithmetic_ops()

pandas/io/formats/format.py

@@ -1123,9 +1123,12 @@ class ExtensionArrayFormatter(GenericArrayFormatter):
     def _format_strings(self):
         values = self.values
         if isinstance(values, (ABCIndexClass, ABCSeries)):
+            boxed = True
             values = values._values
+        else:
+            boxed = False
 
-        formatter = values._formatter(self)
+        formatter = values._formatter(boxed=boxed)
 
         if is_categorical_dtype(values.dtype):
             # Categorical is special for now, so that we can preserve tzinfo