Improvement: Schema tags: added "order" option

marshmallow/decorators.py

@@ -69,7 +69,8 @@ def validates(field_name):
     return tag_processor(VALIDATES, None, False, field_name=field_name)
 
 
-def validates_schema(fn=None, pass_many=False, pass_original=False, skip_on_field_errors=True):
+def validates_schema(fn=None, pass_many=False, pass_original=False, skip_on_field_errors=True,
+                     order=0):
     """Register a schema-level validator.
 
     By default, receives a single object at a time, regardless of whether ``many=True``
@@ -86,51 +87,51 @@ def validates_schema(fn=None, pass_many=False, pass_original=False, skip_on_fiel
         ``skip_on_field_errors`` defaults to `True`.
     """
     return tag_processor(VALIDATES_SCHEMA, fn, pass_many, pass_original=pass_original,
-                         skip_on_field_errors=skip_on_field_errors)
+                         skip_on_field_errors=skip_on_field_errors, order=order)
 
 
-def pre_dump(fn=None, pass_many=False):
+def pre_dump(fn=None, pass_many=False, order=0):
     """Register a method to invoke before serializing an object. The method
     receives the object to be serialized and returns the processed object.
 
     By default, receives a single object at a time, regardless of whether ``many=True``
     is passed to the `Schema`. If ``pass_many=True``, the raw data (which may be a collection)
     and the value for ``many`` is passed.
     """
-    return tag_processor(PRE_DUMP, fn, pass_many)
+    return tag_processor(PRE_DUMP, fn, pass_many, order=order)
 
 
-def post_dump(fn=None, pass_many=False, pass_original=False):
+def post_dump(fn=None, pass_many=False, pass_original=False, order=0):
     """Register a method to invoke after serializing an object. The method
     receives the serialized object and returns the processed object.
 
     By default, receives a single object at a time, transparently handling the ``many``
     argument passed to the Schema. If ``pass_many=True``, the raw data
     (which may be a collection) and the value for ``many`` is passed.
     """
-    return tag_processor(POST_DUMP, fn, pass_many, pass_original=pass_original)
+    return tag_processor(POST_DUMP, fn, pass_many, pass_original=pass_original, order=order)
 
 
-def pre_load(fn=None, pass_many=False):
+def pre_load(fn=None, pass_many=False, order=0):
     """Register a method to invoke before deserializing an object. The method
     receives the data to be deserialized and returns the processed data.
 
     By default, receives a single datum at a time, transparently handling the ``many``
     argument passed to the Schema. If ``pass_many=True``, the raw data
     (which may be a collection) and the value for ``many`` is passed.
     """
-    return tag_processor(PRE_LOAD, fn, pass_many)
+    return tag_processor(PRE_LOAD, fn, pass_many, order=order)
 
 
-def post_load(fn=None, pass_many=False, pass_original=False):
+def post_load(fn=None, pass_many=False, pass_original=False, order=0):
     """Register a method to invoke after deserializing an object. The method
     receives the deserialized data and returns the processed data.
 
     By default, receives a single datum at a time, transparently handling the ``many``
     argument passed to the Schema. If ``pass_many=True``, the raw data
     (which may be a collection) and the value for ``many`` is passed.
     """
-    return tag_processor(POST_LOAD, fn, pass_many, pass_original=pass_original)
+    return tag_processor(POST_LOAD, fn, pass_many, pass_original=pass_original, order=order)
 
 
 def tag_processor(tag_name, fn, pass_many, **kwargs):

marshmallow/schema.py

@@ -164,14 +164,19 @@ def _resolve_processors(self):
 
             try:
                 processor_tags = attr.__marshmallow_tags__
+                processor_kwargs = attr.__marshmallow_kwargs__
             except AttributeError:
                 continue
 
             self._has_processors = bool(processor_tags)
             for tag in processor_tags:
+                order = processor_kwargs[tag].get('order')
                 # Use name here so we can get the bound method later, in case
                 # the processor was a descriptor or something.
-                self.__processors__[tag].append(attr_name)
+                self.__processors__[tag].append((order, attr_name))
+
+        for tag, processors in iteritems(self.__processors__):
+            self.__processors__[tag] = [attr_name for _, attr_name in sorted(processors)]
 
 
 class SchemaOpts(object):