Include metadata in JSONParser output (django-json-api#261)

* Include metadata in Parser output

The JSONParser will add metadata in the request under a top level key '_meta'.

* Documenting parsing metadata in request body

Author: Hamed Ahmadi

docs/api.md

@@ -47,3 +47,14 @@ Calls a `get_root_meta` function on a serializer, if it exists.
 `build_json_resource_obj(fields, resource, resource_instance, resource_name)`
 
 Builds the resource object (type, id, attributes) and extracts relationships.
+
+## rest_framework_json_api.parsers.JSONParser
+
+Similar to `JSONRenderer`, the `JSONParser` you may override the following methods if you need
+highly custom parsing control.
+
+#### parse_metadata
+
+`parse_metadata(result)`
+
+Returns a dictionary which will be merged into parsed data of the request. By default, it reads the `meta` content in the request body and returns it in a dictionary with a `_meta` top level key.

docs/usage.md

@@ -375,7 +375,7 @@ class LineItemViewSet(viewsets.ModelViewSet):
 
 ### RelationshipView
 `rest_framework_json_api.views.RelationshipView` is used to build
-relationship views (see the 
+relationship views (see the
 [JSON API spec](http://jsonapi.org/format/#fetching-relationships)).
 The `self` link on a relationship object should point to the corresponding
 relationship view.
@@ -449,6 +449,8 @@ def get_root_meta(self, resource, many):
 ```
 to the serializer. It must return a dict and will be merged with the existing top level `meta`.
 
+To access metadata in incoming requests, the `JSONParser` will add the metadata under a top level `_meta` key in the parsed data dictionary. For instance, to access meta data from a `serializer` object, you may use `serializer.initial_data.get("_meta")`. To customize the `_meta` key, see [here](api.md).
+
 ### Links
 
 Adding `url` to `fields` on a serializer will add a `self` link to the `links` key.

example/tests/test_parsers.py

@@ -0,0 +1,38 @@
+import json
+
+from django.test import TestCase
+from io import BytesIO
+from rest_framework_json_api.parsers import JSONParser
+
+
+class TestJSONParser(TestCase):
+
+    def setUp(self):
+        class MockRequest(object):
+
+            def __init__(self):
+                self.method = 'GET'
+
+        request = MockRequest()
+
+        self.parser_context = {'request': request, 'kwargs': {}, 'view': 'BlogViewSet'}
+
+        data = {
+            'data': {
+                'id': 123,
+                'type': 'Blog'
+            },
+            'meta': {
+                'random_key': 'random_value'
+            }
+        }
+
+        self.string = json.dumps(data)
+
+    def test_parse_include_metadata(self):
+        parser = JSONParser()
+
+        stream = BytesIO(self.string.encode('utf-8'))
+        data = parser.parse(stream, None, self.parser_context)
+
+        self.assertEqual(data['_meta'], {'random_key': 'random_value'})

rest_framework_json_api/parsers.py

@@ -46,6 +46,14 @@ def parse_relationships(data):
                 parsed_relationships[field_name] = list(relation for relation in field_data)
         return parsed_relationships
 
+    @staticmethod
+    def parse_metadata(result):
+        metadata = result.get('meta')
+        if metadata:
+            return {'_meta': metadata}
+        else:
+            return {}
+
     def parse(self, stream, media_type=None, parser_context=None):
         """
         Parses the incoming bytestream as JSON and returns the resulting data
@@ -87,6 +95,7 @@ def parse(self, stream, media_type=None, parser_context=None):
             parsed_data = {'id': data.get('id')}
             parsed_data.update(self.parse_attributes(data))
             parsed_data.update(self.parse_relationships(data))
+            parsed_data.update(self.parse_metadata(result))
             return parsed_data
 
         else: