Tidy up cursor tests and make more comprehensive

2 files changed, 107 insertions, 135 deletions

diff --git a/rest_framework/pagination.py b/rest_framework/pagination.py
index d5af2ac8..61835239 100644
--- a/rest_framework/pagination.py
+++ b/rest_framework/pagination.py
@@ -171,6 +171,8 @@ class PageNumberPagination(BasePagination):
 
     template = 'rest_framework/pagination/numbers.html'
 
+    invalid_page_message = _('Invalid page "{page_number}": {message}.')
+
     def _handle_backwards_compat(self, view):
         """
         Prior to version 3.1, pagination was handled in the view, and the
@@ -203,7 +205,7 @@ class PageNumberPagination(BasePagination):
         try:
             self.page = paginator.page(page_number)
         except InvalidPage as exc:
-            msg = _('Invalid page "{page_number}": {message}.').format(
+            msg = self.invalid_page_message.format(
                 page_number=page_number, message=six.text_type(exc)
             )
             raise NotFound(msg)
@@ -386,8 +388,8 @@ Cursor = namedtuple('Cursor', ['offset', 'reverse', 'position'])
 
 
 def decode_cursor(encoded):
-    tokens = urlparse.parse_qs(b64decode(encoded), keep_blank_values=True)
     try:
+        tokens = urlparse.parse_qs(b64decode(encoded), keep_blank_values=True)
         offset = int(tokens['offset'][0])
         reverse = bool(int(tokens['reverse'][0]))
         position = tokens['position'][0]
@@ -411,7 +413,8 @@ class CursorPagination(BasePagination):
     # Support case where ordering is already negative
     # Support tuple orderings
     cursor_query_param = 'cursor'
-    page_size = 5
+    page_size = api_settings.PAGINATE_BY
+    invalid_cursor_message = _('Invalid cursor')
 
     def paginate_queryset(self, queryset, request, view=None):
         self.base_url = request.build_absolute_uri()
@@ -424,8 +427,9 @@ class CursorPagination(BasePagination):
             (offset, reverse, current_position) = (0, False, '')
         else:
             self.cursor = decode_cursor(encoded)
+            if self.cursor is None:
+                raise NotFound(self.invalid_cursor_message)
             (offset, reverse, current_position) = self.cursor
-            # TODO: Invalid cursors should 404
 
         # Cursor pagination always enforces an ordering.
         if reverse:
@@ -458,7 +462,7 @@ class CursorPagination(BasePagination):
         # If we have a reverse queryset, then the query ordering was in reverse
         # so we need to reverse the items again before returning them to the user.
         if reverse:
-            self.page = reversed(self.page)
+            self.page = list(reversed(self.page))
 
         if reverse:
             # Determine next and previous positions for reverse cursors.
@@ -483,8 +487,14 @@ class CursorPagination(BasePagination):
         if not self.has_next:
             return None
 
-        compare = self.next_position
+        if self.cursor and self.cursor.reverse and self.cursor.offset != 0:
+            # If we're reversing direction and we have an offset cursor
+            # then we cannot use the first position we find as a marker.
+            compare = self._get_position_from_instance(self.page[-1], self.ordering)
+        else:
+            compare = self.next_position
         offset = 0
+
         for item in reversed(self.page):
             position = self._get_position_from_instance(item, self.ordering)
             if position != compare:
@@ -526,8 +536,14 @@ class CursorPagination(BasePagination):
         if not self.has_previous:
             return None
 
-        compare = self.previous_position
+        if self.cursor and not self.cursor.reverse and self.cursor.offset != 0:
+            # If we're reversing direction and we have an offset cursor
+            # then we cannot use the first position we find as a marker.
+            compare = self._get_position_from_instance(self.page[0], self.ordering)
+        else:
+            compare = self.previous_position
         offset = 0
+
         for item in self.page:
             position = self._get_position_from_instance(item, self.ordering)
             if position != compare:
diff --git a/tests/test_pagination.py b/tests/test_pagination.py
index 4907a080..e32dd028 100644
--- a/tests/test_pagination.py
+++ b/tests/test_pagination.py
@@ -451,171 +451,127 @@ class TestCursorPagination:
 
             def order_by(self, ordering):
                 if ordering.startswith('-'):
-                    return MockQuerySet(reversed(self.items))
+                    return MockQuerySet(list(reversed(self.items)))
                 return self
 
             def __getitem__(self, sliced):
                 return self.items[sliced]
 
-        self.pagination = pagination.CursorPagination()
-        self.queryset = MockQuerySet(
-            [MockObject(idx) for idx in range(1, 16)]
-        )
-
-    def paginate_queryset(self, request):
-        return list(self.pagination.paginate_queryset(self.queryset, request))
-
-    # def get_paginated_content(self, queryset):
-    #     response = self.pagination.get_paginated_response(queryset)
-    #     return response.data
-
-    # def get_html_context(self):
-    #     return self.pagination.get_html_context()
-
-    def test_following_cursor(self):
-        request = Request(factory.get('/'))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 2, 3, 4, 5]
-
-        next_url = self.pagination.get_next_link()
-        assert next_url
+        class ExamplePagination(pagination.CursorPagination):
+            page_size = 5
 
-        request = Request(factory.get(next_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [6, 7, 8, 9, 10]
+        self.pagination = ExamplePagination()
+        self.queryset = MockQuerySet([
+            MockObject(idx) for idx in [
+                1, 1, 1, 1, 1,
+                1, 2, 3, 4, 4,
+                4, 4, 5, 6, 7,
+                7, 7, 7, 7, 7,
+                7, 7, 7, 8, 9,
+                9, 9, 9, 9, 9
+            ]
+        ])
 
-        next_url = self.pagination.get_next_link()
-        assert next_url
+    def get_pages(self, url):
+        """
+        Given a URL return a tuple of:
 
-        request = Request(factory.get(next_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [11, 12, 13, 14, 15]
+        (previous page, current page, next page, previous url, next url)
+        """
+        request = Request(factory.get(url))
+        queryset = self.pagination.paginate_queryset(self.queryset, request)
+        current = [item.created for item in queryset]
 
         next_url = self.pagination.get_next_link()
-        assert next_url is None
-
-        # Now page back again
-
         previous_url = self.pagination.get_previous_link()
-        assert previous_url
 
-        request = Request(factory.get(previous_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [6, 7, 8, 9, 10]
+        if next_url is not None:
+            request = Request(factory.get(next_url))
+            queryset = self.pagination.paginate_queryset(self.queryset, request)
+            next = [item.created for item in queryset]
+        else:
+            next = None
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url
+        if previous_url is not None:
+            request = Request(factory.get(previous_url))
+            queryset = self.pagination.paginate_queryset(self.queryset, request)
+            previous = [item.created for item in queryset]
+        else:
+            previous = None
 
-        request = Request(factory.get(previous_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 2, 3, 4, 5]
+        return (previous, current, next, previous_url, next_url)
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url is None
-
-
-class TestCrazyCursorPagination:
-    """
-    Unit tests for `pagination.CursorPagination`.
-    """
-
-    def setup(self):
-        class MockObject(object):
-            def __init__(self, idx):
-                self.created = idx
-
-        class MockQuerySet(object):
-            def __init__(self, items):
-                self.items = items
+    def test_invalid_cursor(self):
+        request = Request(factory.get('/', {'cursor': '123'}))
+        with pytest.raises(exceptions.NotFound):
+            self.pagination.paginate_queryset(self.queryset, request)
 
-            def filter(self, created__gt=None, created__lt=None):
-                if created__gt is not None:
-                    return MockQuerySet([
-                        item for item in self.items
-                        if item.created > int(created__gt)
-                    ])
+    def test_cursor_pagination(self):
+        (previous, current, next, previous_url, next_url) = self.get_pages('/')
 
-                assert created__lt is not None
-                return MockQuerySet([
-                    item for item in self.items
-                    if item.created < int(created__lt)
-                ])
+        assert previous is None
+        assert current == [1, 1, 1, 1, 1]
+        assert next == [1, 2, 3, 4, 4]
 
-            def order_by(self, ordering):
-                if ordering.startswith('-'):
-                    return MockQuerySet(reversed(self.items))
-                return self
+        (previous, current, next, previous_url, next_url) = self.get_pages(next_url)
 
-            def __getitem__(self, sliced):
-                return self.items[sliced]
+        assert previous == [1, 1, 1, 1, 1]
+        assert current == [1, 2, 3, 4, 4]
+        assert next == [4, 4, 5, 6, 7]
 
-        self.pagination = pagination.CursorPagination()
-        self.queryset = MockQuerySet([
-            MockObject(idx) for idx in [
-                1, 1, 1, 1, 1,
-                1, 1, 1, 1, 1,
-                1, 1, 2, 3, 4,
-                5, 6, 7, 8, 9
-            ]
-        ])
+        (previous, current, next, previous_url, next_url) = self.get_pages(next_url)
 
-    def paginate_queryset(self, request):
-        return list(self.pagination.paginate_queryset(self.queryset, request))
+        assert previous == [1, 2, 3, 4, 4]
+        assert current == [4, 4, 5, 6, 7]
+        assert next == [7, 7, 7, 7, 7]
 
-    def test_following_cursor_identical_items(self):
-        request = Request(factory.get('/'))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 1, 1, 1]
+        (previous, current, next, previous_url, next_url) = self.get_pages(next_url)
 
-        next_url = self.pagination.get_next_link()
-        assert next_url
+        assert previous == [4, 4, 4, 5, 6]  # Paging artifact
+        assert current == [7, 7, 7, 7, 7]
+        assert next == [7, 7, 7, 8, 9]
 
-        request = Request(factory.get(next_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 1, 1, 1]
+        (previous, current, next, previous_url, next_url) = self.get_pages(next_url)
 
-        next_url = self.pagination.get_next_link()
-        assert next_url
+        assert previous == [7, 7, 7, 7, 7]
+        assert current == [7, 7, 7, 8, 9]
+        assert next == [9, 9, 9, 9, 9]
 
-        request = Request(factory.get(next_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 2, 3, 4]
+        (previous, current, next, previous_url, next_url) = self.get_pages(next_url)
 
-        next_url = self.pagination.get_next_link()
-        assert next_url
+        assert previous == [7, 7, 7, 8, 9]
+        assert current == [9, 9, 9, 9, 9]
+        assert next is None
 
-        request = Request(factory.get(next_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [5, 6, 7, 8, 9]
+        (previous, current, next, previous_url, next_url) = self.get_pages(previous_url)
 
-        next_url = self.pagination.get_next_link()
-        assert next_url is None
+        assert previous == [7, 7, 7, 7, 7]
+        assert current == [7, 7, 7, 8, 9]
+        assert next == [9, 9, 9, 9, 9]
 
-        # Now page back again
+        (previous, current, next, previous_url, next_url) = self.get_pages(previous_url)
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url
+        assert previous == [4, 4, 5, 6, 7]
+        assert current == [7, 7, 7, 7, 7]
+        assert next == [8, 9, 9, 9, 9]  # Paging artifact
 
-        request = Request(factory.get(previous_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 2, 3, 4]
+        (previous, current, next, previous_url, next_url) = self.get_pages(previous_url)
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url
+        assert previous == [1, 2, 3, 4, 4]
+        assert current == [4, 4, 5, 6, 7]
+        assert next == [7, 7, 7, 7, 7]
 
-        request = Request(factory.get(previous_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 1, 1, 1]
+        (previous, current, next, previous_url, next_url) = self.get_pages(previous_url)
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url
+        assert previous == [1, 1, 1, 1, 1]
+        assert current == [1, 2, 3, 4, 4]
+        assert next == [4, 4, 5, 6, 7]
 
-        request = Request(factory.get(previous_url))
-        queryset = self.paginate_queryset(request)
-        assert [item.created for item in queryset] == [1, 1, 1, 1, 1]
+        (previous, current, next, previous_url, next_url) = self.get_pages(previous_url)
 
-        previous_url = self.pagination.get_previous_link()
-        assert previous_url is None
+        assert previous is None
+        assert current == [1, 1, 1, 1, 1]
+        assert next == [1, 2, 3, 4, 4]
 
 
 def test_get_displayed_page_numbers():