SearchFilter to support JSONField and HStoreField (#7121)

* SearchFilter to support Custom query Transforms

Since Some fields support `__` as a custom Transform for query lookups we needed to update the m2m checking code to handle search_fields that contain __ that are not relationships.

* Update documentation on SearchFilter to include references to JSON and HStore Fields.

docs/api-guide/filtering.md

@@ -206,6 +206,10 @@ You can also perform a related lookup on a ForeignKey or ManyToManyField with th
 
     search_fields = ['username', 'email', 'profile__profession']
     
+For [JSONField][JSONField] and [HStoreField][HStoreField] fields you can filter based on nested values within the data structure using the same double-underscore notation:
+
+    search_fields = ['data__breed', 'data__owner__other_pets__0__name']
+
 By default, searches will use case-insensitive partial matches.  The search parameter may contain multiple search terms, which should be whitespace and/or comma separated.  If multiple search terms are used then objects will be returned in the list only if all the provided terms are matched.
 
 The search behavior may be restricted by prepending various characters to the `search_fields`.
@@ -360,3 +364,5 @@ The [djangorestframework-word-filter][django-rest-framework-word-search-filter]
 [django-rest-framework-word-search-filter]: https://github.com/trollknurr/django-rest-framework-word-search-filter
 [django-url-filter]: https://github.com/miki725/django-url-filter
 [drf-url-filter]: https://github.com/manjitkumar/drf-url-filters
+[HStoreField]: https://docs.djangoproject.com/en/3.0/ref/contrib/postgres/fields/#hstorefield
+[JSONField]: https://docs.djangoproject.com/en/3.0/ref/contrib/postgres/fields/#jsonfield

rest_framework/filters.py

@@ -96,6 +96,9 @@ class SearchFilter(BaseFilterBackend):
                     if any(path.m2m for path in path_info):
                         # This field is a m2m relation so we know we need to call distinct
                         return True
+                else:
+                    # This field has a custom __ query transform but is not a relational field.
+                    break
         return False
 
     def filter_queryset(self, request, queryset, view):

tests/test_filters.py

@@ -1,9 +1,11 @@
 import datetime
 from importlib import reload as reload_module
 
+import django
 import pytest
 from django.core.exceptions import ImproperlyConfigured
 from django.db import models
+from django.db.models import CharField, Transform
 from django.db.models.functions import Concat, Upper
 from django.test import TestCase
 from django.test.utils import override_settings
@@ -189,6 +191,42 @@ class SearchFilterTests(TestCase):
 
         assert terms == ['asdf']
 
+    @pytest.mark.skipif(django.VERSION[:2] < (2, 2), reason="requires django 2.2 or higher")
+    def test_search_field_with_additional_transforms(self):
+        from django.test.utils import register_lookup
+
+        class SearchListView(generics.ListAPIView):
+            queryset = SearchFilterModel.objects.all()
+            serializer_class = SearchFilterSerializer
+            filter_backends = (filters.SearchFilter,)
+            search_fields = ('text__trim', )
+
+        view = SearchListView.as_view()
+
+        # an example custom transform, that trims `a` from the string.
+        class TrimA(Transform):
+            function = 'TRIM'
+            lookup_name = 'trim'
+
+            def as_sql(self, compiler, connection):
+                sql, params = compiler.compile(self.lhs)
+                return "trim(%s, 'a')" % sql, params
+
+        with register_lookup(CharField, TrimA):
+            # Search including `a`
+            request = factory.get('/', {'search': 'abc'})
+
+            response = view(request)
+            assert response.data == []
+
+            # Search excluding `a`
+            request = factory.get('/', {'search': 'bc'})
+            response = view(request)
+            assert response.data == [
+                {'id': 1, 'title': 'z', 'text': 'abc'},
+                {'id': 2, 'title': 'zz', 'text': 'bcd'},
+            ]
+
 
 class AttributeModel(models.Model):
     label = models.CharField(max_length=32)