From 648ce5864e4b165e1c626e072385e2cf99679a88 Mon Sep 17 00:00:00 2001
From: George Dunning <georgedunning98@gmail.com>
Date: Sun, 13 Mar 2022 15:25:41 +0000
Subject: [PATCH] Add get_django_paginator_class method to PageNumberPagination

This enables the pagination class to be overridden conditionally.
---
 rest_framework/pagination.py |  8 +++++--
 tests/test_pagination.py     | 43 ++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/rest_framework/pagination.py b/rest_framework/pagination.py
index e815d8d5c..c2357c9ca 100644
--- a/rest_framework/pagination.py
+++ b/rest_framework/pagination.py
@@ -193,11 +193,13 @@ class PageNumberPagination(BasePagination):
         Paginate a queryset if required, either returning a
         page object, or `None` if pagination is not configured for this view.
         """
+        self.request = request
+
         page_size = self.get_page_size(request)
         if not page_size:
             return None
 
-        paginator = self.django_paginator_class(queryset, page_size)
+        paginator = self.get_django_paginator_class()(queryset, page_size)
         page_number = self.get_page_number(request, paginator)
 
         try:
@@ -212,7 +214,6 @@ class PageNumberPagination(BasePagination):
             # The browsable API should display pagination controls.
             self.display_page_controls = True
 
-        self.request = request
         return list(self.page)
 
     def get_page_number(self, request, paginator):
@@ -304,6 +305,9 @@ class PageNumberPagination(BasePagination):
             'page_links': page_links
         }
 
+    def get_django_paginator_class(self):
+        return self.django_paginator_class
+
     def to_html(self):
         template = loader.get_template(self.template)
         context = self.get_html_context()
diff --git a/tests/test_pagination.py b/tests/test_pagination.py
index c028f0ea8..a589adccd 100644
--- a/tests/test_pagination.py
+++ b/tests/test_pagination.py
@@ -308,6 +308,8 @@ class TestPageNumberPaginationOverride:
             # we will only return one page, with one item
             count = 1
 
+        self.paginator = OverriddenDjangoPaginator
+
         class ExamplePagination(pagination.PageNumberPagination):
             django_paginator_class = OverriddenDjangoPaginator
             page_size = 5
@@ -352,6 +354,47 @@ class TestPageNumberPaginationOverride:
         with pytest.raises(exceptions.NotFound):
             self.paginate_queryset(request)
 
+    def test_no_page_number_override_using_get_django_paginator_class(self):
+
+        paginator = self.paginator
+
+        class UrlSpecifiedPagination(pagination.PageNumberPagination):
+            page_size = 5
+
+            def get_django_paginator_class(self):
+                """
+                Set the pagination class based on URL parameters.
+                """
+                if self.request.GET.get("pagination_mode") == "overridden":
+                    return paginator
+                else:
+                    raise NotImplementedError(
+                        "The test data should not trigger this branch."
+                    )
+
+        self.pagination = UrlSpecifiedPagination()
+
+        request = Request(factory.get('/', data={'pagination_mode': 'overridden'}))
+        queryset = self.paginate_queryset(request)
+        content = self.get_paginated_content(queryset)
+        context = self.get_html_context()
+        assert queryset == [1]
+        assert content == {
+            'results': [1, ],
+            'previous': None,
+            'next': None,
+            'count': 1
+        }
+        assert context == {
+            'previous_url': None,
+            'next_url': None,
+            'page_links': [
+                PageLink('http://testserver/?pagination_mode=overridden', 1, True, False),
+            ]
+        }
+        assert not self.pagination.display_page_controls
+        assert isinstance(self.pagination.to_html(), str)
+
 
 class TestLimitOffset:
     """