Let SearchFilter subclasses dynamically set search fields

docs/api-guide/filtering.md

@@ -218,6 +218,13 @@ For example:
 
 By default, the search parameter is named `'search`', but this may be overridden with the `SEARCH_PARAM` setting.
 
+To dynamically change search fields based on request content, it's possible to subclass the `SearchFilter` and override the `get_search_fields()` function. For example, the following subclass will only search on `title` if the query parameter `title_only` is in the request:
+
+    class CustomSearchFilter(self, view, request):
+        if request.query_params.get('title_only'):
+            return ('title',)
+        return super(CustomSearchFilter, self).get_search_fields(view, request)
+
 For more details, see the [Django documentation][search-django-admin].
 
 ---

rest_framework/filters.py

@@ -53,6 +53,14 @@ class SearchFilter(BaseFilterBackend):
     search_title = _('Search')
     search_description = _('A search term.')
 
+    def get_search_fields(self, view, request):
+        """
+        Search fields are obtained from the view, but the request is always
+        passed to this method. Sub-classes can override this method to
+        dynamically change the search fields based on request content.
+        """
+        return getattr(view, 'search_fields', None)
+
     def get_search_terms(self, request):
         """
         Search terms are set by a ?search=... query parameter,
@@ -90,7 +98,7 @@ def must_call_distinct(self, queryset, search_fields):
         return False
 
     def filter_queryset(self, request, queryset, view):
-        search_fields = getattr(view, 'search_fields', None)
+        search_fields = self.get_search_fields(view, request)
         search_terms = self.get_search_terms(request)
 
         if not search_fields or not search_terms:

tests/test_filters.py

@@ -156,6 +156,31 @@ class SearchListView(generics.ListAPIView):
 
         reload_module(filters)
 
+    def test_search_with_filter_subclass(self):
+        class CustomSearchFilter(filters.SearchFilter):
+            # Filter that dynamically changes search fields
+            def get_search_fields(self, view, request):
+                if request.query_params.get('title_only'):
+                    return ('$title',)
+                return super(CustomSearchFilter, self).get_search_fields(view, request)
+
+        class SearchListView(generics.ListAPIView):
+            queryset = SearchFilterModel.objects.all()
+            serializer_class = SearchFilterSerializer
+            filter_backends = (CustomSearchFilter,)
+            search_fields = ('$title', '$text')
+
+        view = SearchListView.as_view()
+        request = factory.get('/', {'search': '^\w{3}$'})
+        response = view(request)
+        assert len(response.data) == 10
+
+        request = factory.get('/', {'search': '^\w{3}$', 'title_only': 'true'})
+        response = view(request)
+        assert response.data == [
+            {'id': 3, 'title': 'zzz', 'text': 'cde'}
+        ]
+
 
 class AttributeModel(models.Model):
     label = models.CharField(max_length=32)