Merge branch 'cursor-limits' of…

Merge branch 'cursor-limits' of https://github.com/uploadcare/django-rest-framework into uploadcare-cursor-limits

rest_framework/pagination.py

@@ -449,13 +449,26 @@ class CursorPagination(BasePagination):
     http://cramer.io/2011/03/08/building-cursors-for-the-disqus-api/
     """
     cursor_query_param = 'cursor'
+
+    # The default page size.
+    # Defaults to `None`, meaning pagination is disabled.
     page_size = api_settings.PAGE_SIZE
+
+    # Client can control the page size using this query parameter.
+    # Default is 'None'. Set to eg 'page_size' to enable usage.
+    page_size_query_param = None
+
+    # Set to an integer to limit the maximum page size the client may request.
+    # Only relevant if 'page_size_query_param' has also been set.
+    max_page_size = None
+
     invalid_cursor_message = _('Invalid cursor')
     ordering = '-created'
     template = 'rest_framework/pagination/previous_and_next.html'
 
     def paginate_queryset(self, queryset, request, view=None):
-        if self.page_size is None:
+        self.page_size = self.get_page_size(request)
+        if not self.page_size:
             return None
 
         self.base_url = request.build_absolute_uri()
@@ -530,6 +543,19 @@ class CursorPagination(BasePagination):
 
         return self.page
 
+    def get_page_size(self, request):
+        if self.page_size_query_param:
+            try:
+                return _positive_int(
+                    request.query_params[self.page_size_query_param],
+                    strict=True,
+                    cutoff=self.max_page_size
+                )
+            except (KeyError, ValueError):
+                pass
+
+        return self.page_size
+
     def get_next_link(self):
         if not self.has_next:
             return None

tests/test_pagination.py

@@ -513,6 +513,8 @@ class TestCursorPagination:
 
         class ExamplePagination(pagination.CursorPagination):
             page_size = 5
+            page_size_query_param = 'page_size'
+            max_page_size = 20
             ordering = 'created'
 
         self.pagination = ExamplePagination()
@@ -648,6 +650,24 @@ class TestCursorPagination:
 
         assert isinstance(self.pagination.to_html(), type(''))
 
+    def test_page_size(self):
+        (previous, current, next, previous_url, next_url) = \
+            self.get_pages('/?page_size=10')
+
+        assert previous is None
+        assert current == [1, 1, 1, 1, 1, 1, 2, 3, 4, 4]
+        assert next == [4, 4, 5, 6, 7, 7, 7, 7, 7, 7]
+        assert 'page_size=10' in next_url
+
+        (previous, current, next, previous_url, next_url) = \
+            self.get_pages(next_url.replace('page_size=10', 'page_size=4'))
+
+        assert previous == [2, 3, 4, 4]
+        assert current == [4, 4, 5, 6]
+        assert next == [7, 7, 7, 7]
+        assert 'page_size=4' in previous_url
+        assert 'page_size=4' in next_url
+
 
 def test_get_displayed_page_numbers():
     """