Fixed #25513 -- Extracted admin pagination to Paginator.get_elided_page_range().

2 files changed, 139 insertions, 18 deletions

diff --git a/tests/admin_changelist/tests.py b/tests/admin_changelist/tests.py
index bd4d406c10..28acc401c1 100644
--- a/tests/admin_changelist/tests.py
+++ b/tests/admin_changelist/tests.py
@@ -1242,32 +1242,32 @@ class ChangeListTests(TestCase):
         request = self.factory.get('/group/')
         request.user = self.superuser
         cl = m.get_changelist_instance(request)
-        per_page = cl.list_per_page = 10
+        cl.list_per_page = 10
 
-        for page_num, objects_count, expected_page_range in [
-            (1, per_page, []),
-            (1, per_page * 2, [1, 2]),
-            (6, per_page * 11, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]),
-            (6, per_page * 12, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]),
-            (6, per_page * 13, [1, 2, 3, 4, 5, 6, 7, 8, 9, '.', 12, 13]),
-            (7, per_page * 12, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]),
-            (7, per_page * 13, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]),
-            (7, per_page * 14, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, '.', 13, 14]),
-            (8, per_page * 13, [1, 2, '.', 5, 6, 7, 8, 9, 10, 11, 12, 13]),
-            (8, per_page * 14, [1, 2, '.', 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]),
-            (8, per_page * 15, [1, 2, '.', 5, 6, 7, 8, 9, 10, 11, '.', 14, 15]),
+        ELLIPSIS = cl.paginator.ELLIPSIS
+        for number, pages, expected in [
+            (1, 1, []),
+            (1, 2, [1, 2]),
+            (6, 11, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]),
+            (6, 12, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]),
+            (6, 13, [1, 2, 3, 4, 5, 6, 7, 8, 9, ELLIPSIS, 12, 13]),
+            (7, 12, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]),
+            (7, 13, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]),
+            (7, 14, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ELLIPSIS, 13, 14]),
+            (8, 13, [1, 2, ELLIPSIS, 5, 6, 7, 8, 9, 10, 11, 12, 13]),
+            (8, 14, [1, 2, ELLIPSIS, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]),
+            (8, 15, [1, 2, ELLIPSIS, 5, 6, 7, 8, 9, 10, 11, ELLIPSIS, 14, 15]),
         ]:
             with self.subTest(number=number, pages=pages):
-                # assuming exactly `objects_count` objects
+                # assuming exactly `pages * cl.list_per_page` objects
                 Group.objects.all().delete()
-                for i in range(objects_count):
+                for i in range(pages * cl.list_per_page):
                     Group.objects.create(name='test band')
 
                 # setting page number and calculating page range
-                cl.page_num = page_num
+                cl.page_num = number
                 cl.get_results(request)
-                real_page_range = pagination(cl)['page_range']
-                self.assertEqual(expected_page_range, list(real_page_range))
+                self.assertEqual(list(pagination(cl)['page_range']), expected)
 
     def test_object_tools_displayed_no_add_permission(self):
         """
diff --git a/tests/pagination/tests.py b/tests/pagination/tests.py
index f82d333ae7..d781bdf8a7 100644
--- a/tests/pagination/tests.py
+++ b/tests/pagination/tests.py
@@ -1,3 +1,5 @@
+import collections.abc
+import unittest.mock
 import warnings
 from datetime import datetime
 
@@ -304,6 +306,125 @@ class PaginationTests(SimpleTestCase):
             with self.subTest(page=page):
                 self.assertEqual(expected, list(next(page_iterator)))
 
+    def test_get_elided_page_range(self):
+        # Paginator.validate_number() must be called:
+        paginator = Paginator([1, 2, 3], 2)
+        with unittest.mock.patch.object(paginator, 'validate_number') as mock:
+            mock.assert_not_called()
+            list(paginator.get_elided_page_range(2))
+            mock.assert_called_with(2)
+
+        ELLIPSIS = Paginator.ELLIPSIS
+
+        # Range is not elided if not enough pages when using default arguments:
+        paginator = Paginator(range(10 * 100), 100)
+        page_range = paginator.get_elided_page_range(1)
+        self.assertIsInstance(page_range, collections.abc.Generator)
+        self.assertNotIn(ELLIPSIS, page_range)
+        paginator = Paginator(range(10 * 100 + 1), 100)
+        self.assertIsInstance(page_range, collections.abc.Generator)
+        page_range = paginator.get_elided_page_range(1)
+        self.assertIn(ELLIPSIS, page_range)
+
+        # Range should be elided if enough pages when using default arguments:
+        tests = [
+            # on_each_side=3, on_ends=2
+            (1, [1, 2, 3, 4, ELLIPSIS, 49, 50]),
+            (6, [1, 2, 3, 4, 5, 6, 7, 8, 9, ELLIPSIS, 49, 50]),
+            (7, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ELLIPSIS, 49, 50]),
+            (8, [1, 2, ELLIPSIS, 5, 6, 7, 8, 9, 10, 11, ELLIPSIS, 49, 50]),
+            (43, [1, 2, ELLIPSIS, 40, 41, 42, 43, 44, 45, 46, ELLIPSIS, 49, 50]),
+            (44, [1, 2, ELLIPSIS, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50]),
+            (45, [1, 2, ELLIPSIS, 42, 43, 44, 45, 46, 47, 48, 49, 50]),
+            (50, [1, 2, ELLIPSIS, 47, 48, 49, 50]),
+        ]
+        paginator = Paginator(range(5000), 100)
+        for number, expected in tests:
+            with self.subTest(number=number):
+                page_range = paginator.get_elided_page_range(number)
+                self.assertIsInstance(page_range, collections.abc.Generator)
+                self.assertEqual(list(page_range), expected)
+
+        # Range is not elided if not enough pages when using custom arguments:
+        tests = [
+            (6, 2, 1, 1), (8, 1, 3, 1), (8, 4, 0, 1), (4, 1, 1, 1),
+            # When on_each_side and on_ends are both <= 1 but not both == 1 it
+            # is a special case where the range is not elided until an extra
+            # page is added.
+            (2, 0, 1, 2), (2, 1, 0, 2), (1, 0, 0, 2),
+        ]
+        for pages, on_each_side, on_ends, elided_after in tests:
+            for offset in range(elided_after + 1):
+                with self.subTest(pages=pages, offset=elided_after, on_each_side=on_each_side, on_ends=on_ends):
+                    paginator = Paginator(range((pages + offset) * 100), 100)
+                    page_range = paginator.get_elided_page_range(
+                        1,
+                        on_each_side=on_each_side,
+                        on_ends=on_ends,
+                    )
+                    self.assertIsInstance(page_range, collections.abc.Generator)
+                    if offset < elided_after:
+                        self.assertNotIn(ELLIPSIS, page_range)
+                    else:
+                        self.assertIn(ELLIPSIS, page_range)
+
+        # Range should be elided if enough pages when using custom arguments:
+        tests = [
+            # on_each_side=2, on_ends=1
+            (1, 2, 1, [1, 2, 3, ELLIPSIS, 50]),
+            (4, 2, 1, [1, 2, 3, 4, 5, 6, ELLIPSIS, 50]),
+            (5, 2, 1, [1, 2, 3, 4, 5, 6, 7, ELLIPSIS, 50]),
+            (6, 2, 1, [1, ELLIPSIS, 4, 5, 6, 7, 8, ELLIPSIS, 50]),
+            (45, 2, 1, [1, ELLIPSIS, 43, 44, 45, 46, 47, ELLIPSIS, 50]),
+            (46, 2, 1, [1, ELLIPSIS, 44, 45, 46, 47, 48, 49, 50]),
+            (47, 2, 1, [1, ELLIPSIS, 45, 46, 47, 48, 49, 50]),
+            (50, 2, 1, [1, ELLIPSIS, 48, 49, 50]),
+            # on_each_side=1, on_ends=3
+            (1, 1, 3, [1, 2, ELLIPSIS, 48, 49, 50]),
+            (5, 1, 3, [1, 2, 3, 4, 5, 6, ELLIPSIS, 48, 49, 50]),
+            (6, 1, 3, [1, 2, 3, 4, 5, 6, 7, ELLIPSIS, 48, 49, 50]),
+            (7, 1, 3, [1, 2, 3, ELLIPSIS, 6, 7, 8, ELLIPSIS, 48, 49, 50]),
+            (44, 1, 3, [1, 2, 3, ELLIPSIS, 43, 44, 45, ELLIPSIS, 48, 49, 50]),
+            (45, 1, 3, [1, 2, 3, ELLIPSIS, 44, 45, 46, 47, 48, 49, 50]),
+            (46, 1, 3, [1, 2, 3, ELLIPSIS, 45, 46, 47, 48, 49, 50]),
+            (50, 1, 3, [1, 2, 3, ELLIPSIS, 49, 50]),
+            # on_each_side=4, on_ends=0
+            (1, 4, 0, [1, 2, 3, 4, 5, ELLIPSIS]),
+            (5, 4, 0, [1, 2, 3, 4, 5, 6, 7, 8, 9, ELLIPSIS]),
+            (6, 4, 0, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ELLIPSIS]),
+            (7, 4, 0, [ELLIPSIS, 3, 4, 5, 6, 7, 8, 9, 10, 11, ELLIPSIS]),
+            (44, 4, 0, [ELLIPSIS, 40, 41, 42, 43, 44, 45, 46, 47, 48, ELLIPSIS]),
+            (45, 4, 0, [ELLIPSIS, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50]),
+            (46, 4, 0, [ELLIPSIS, 42, 43, 44, 45, 46, 47, 48, 49, 50]),
+            (50, 4, 0, [ELLIPSIS, 46, 47, 48, 49, 50]),
+            # on_each_side=0, on_ends=1
+            (1, 0, 1, [1, ELLIPSIS, 50]),
+            (2, 0, 1, [1, 2, ELLIPSIS, 50]),
+            (3, 0, 1, [1, 2, 3, ELLIPSIS, 50]),
+            (4, 0, 1, [1, ELLIPSIS, 4, ELLIPSIS, 50]),
+            (47, 0, 1, [1, ELLIPSIS, 47, ELLIPSIS, 50]),
+            (48, 0, 1, [1, ELLIPSIS, 48, 49, 50]),
+            (49, 0, 1, [1, ELLIPSIS, 49, 50]),
+            (50, 0, 1, [1, ELLIPSIS, 50]),
+            # on_each_side=0, on_ends=0
+            (1, 0, 0, [1, ELLIPSIS]),
+            (2, 0, 0, [1, 2, ELLIPSIS]),
+            (3, 0, 0, [ELLIPSIS, 3, ELLIPSIS]),
+            (48, 0, 0, [ELLIPSIS, 48, ELLIPSIS]),
+            (49, 0, 0, [ELLIPSIS, 49, 50]),
+            (50, 0, 0, [ELLIPSIS, 50]),
+        ]
+        paginator = Paginator(range(5000), 100)
+        for number, on_each_side, on_ends, expected in tests:
+            with self.subTest(number=number, on_each_side=on_each_side, on_ends=on_ends):
+                page_range = paginator.get_elided_page_range(
+                    number,
+                    on_each_side=on_each_side,
+                    on_ends=on_ends,
+                )
+                self.assertIsInstance(page_range, collections.abc.Generator)
+                self.assertEqual(list(page_range), expected)
+
 
 class ModelPaginationTests(TestCase):
     """