Include meta section for SerializerMethodResourceRelatedField(many=True) (#1162)

Fixes #572

Author: arttuperala

CHANGELOG.md

@@ -40,6 +40,8 @@ any parts of the framework not mentioned in the documentation should generally b
             return value.name
     ```
 
+* `SerializerMethodResourceRelatedField(many=True)` relationship data now includes a meta section.
+
 ### Fixed
 
 * Refactored handling of the `sort` query parameter to fix duplicate declaration in the generated schema definition

example/tests/integration/test_non_paginated_responses.py

@@ -51,6 +51,7 @@ def test_multiple_entries_no_pagination(multiple_entries, client):
                             "related": "http://testserver/entries/1/suggested/",
                             "self": "http://testserver/entries/1/relationships/suggested",
                         },
+                        "meta": {"count": 1},
                     },
                     "suggestedHyperlinked": {
                         "links": {
@@ -106,6 +107,7 @@ def test_multiple_entries_no_pagination(multiple_entries, client):
                             "related": "http://testserver/entries/2/suggested/",
                             "self": "http://testserver/entries/2/relationships/suggested",
                         },
+                        "meta": {"count": 1},
                     },
                     "suggestedHyperlinked": {
                         "links": {

example/tests/integration/test_pagination.py

@@ -51,6 +51,7 @@ def test_pagination_with_single_entry(single_entry, client):
                             "related": "http://testserver/entries/1/suggested/",
                             "self": "http://testserver/entries/1/relationships/suggested",
                         },
+                        "meta": {"count": 0},
                     },
                     "suggestedHyperlinked": {
                         "links": {

example/tests/test_filters.py

@@ -512,6 +512,7 @@ def test_search_keywords(self):
                                 {"type": "entries", "id": "11"},
                                 {"type": "entries", "id": "12"},
                             ],
+                            "meta": {"count": 11},
                         },
                         "suggestedHyperlinked": {
                             "links": {

rest_framework_json_api/renderers.py

@@ -19,6 +19,7 @@
 from rest_framework_json_api import utils
 from rest_framework_json_api.relations import (
     HyperlinkedMixin,
+    ManySerializerMethodResourceRelatedField,
     ResourceRelatedField,
     SkipDataMixin,
 )
@@ -152,6 +153,11 @@ def extract_relationships(cls, fields, resource, resource_instance):
                 if not isinstance(field, SkipDataMixin):
                     relation_data.update({"data": resource.get(field_name)})
 
+                    if isinstance(field, ManySerializerMethodResourceRelatedField):
+                        relation_data.update(
+                            {"meta": {"count": len(resource.get(field_name))}}
+                        )
+
                 data.update({field_name: relation_data})
                 continue