Support null values in parsers when services accepts and returns null values.

botocore/model.py

@@ -121,6 +121,7 @@ def __init__(self, shape_name, shape_model, shape_resolver=None):
         """
         self.name = shape_name
         self.type_name = shape_model['type']
+        self.boxed = shape_model.get('box', False)
         self.documentation = shape_model.get('documentation', '')
         self._shape_model = shape_model
         if shape_resolver is None:

botocore/parsers.py

@@ -194,6 +194,15 @@ class ResponseParserError(Exception):
     pass
 
 
+def box_decorator(func):
+    def handle_box(self, shape, value):
+        if shape.boxed and value is None:
+            return None
+        return func(self, shape, value)
+
+    return handle_box
+
+
 class ResponseParser:
     """Base class for response parsing.
 
@@ -340,10 +349,18 @@ def _do_modeled_error_parse(self, response, shape, parsed):
             f"{self.__class__.__name__}._do_modeled_error_parse"
         )
 
+    BOXABLE_PRIMITIVE_TYPES = ["long", "integer", "boolean"]
+
     def _parse_shape(self, shape, node):
         handler = getattr(
             self, f'_handle_{shape.type_name}', self._default_handle
         )
+        if (
+            shape.type_name in self.BOXABLE_PRIMITIVE_TYPES
+            and shape.boxed
+            and node is None
+        ):
+            return None
         return handler(shape, node)
 
     def _handle_list(self, shape, node):