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

2 files changed, 37 insertions, 36 deletions

diff --git a/django/contrib/admin/templatetags/admin_list.py b/django/contrib/admin/templatetags/admin_list.py
index 5c8d21d30d..f4b6d8d59f 100644
--- a/django/contrib/admin/templatetags/admin_list.py
+++ b/django/contrib/admin/templatetags/admin_list.py
@@ -24,16 +24,14 @@ from .base import InclusionAdminNode
 
 register = Library()
 
-DOT = '.'
-
 
 @register.simple_tag
 def paginator_number(cl, i):
     """
     Generate an individual page index link in a paginated list.
     """
-    if i == DOT:
-        return '… '
+    if i == cl.paginator.ELLIPSIS:
+        return format_html('{} ', cl.paginator.ELLIPSIS)
     elif i == cl.page_num:
         return format_html('<span class="this-page">{}</span> ', i)
     else:
@@ -49,39 +47,8 @@ def pagination(cl):
     """
     Generate the series of links to the pages in a paginated list.
     """
-    paginator, page_num = cl.paginator, cl.page_num
-
     pagination_required = (not cl.show_all or not cl.can_show_all) and cl.multi_page
-    if not pagination_required:
-        page_range = []
-    else:
-        ON_EACH_SIDE = 3
-        ON_ENDS = 2
-
-        # If there are 10 or fewer pages, display links to every page.
-        # Otherwise, do some fancy
-        if paginator.num_pages <= 10:
-            page_range = range(1, paginator.num_pages + 1)
-        else:
-            # Insert "smart" pagination links, so that there are always ON_ENDS
-            # links at either end of the list of pages, and there are always
-            # ON_EACH_SIDE links at either end of the "current page" link.
-            page_range = []
-            if page_num > (1 + ON_EACH_SIDE + ON_ENDS) + 1:
-                page_range += [
-                    *range(1, ON_ENDS + 1), DOT,
-                    *range(page_num - ON_EACH_SIDE, page_num + 1),
-                ]
-            else:
-                page_range.extend(range(1, page_num + 1))
-            if page_num < (paginator.num_pages - ON_EACH_SIDE - ON_ENDS) - 1:
-                page_range += [
-                    *range(page_num + 1, page_num + ON_EACH_SIDE + 1), DOT,
-                    *range(paginator.num_pages - ON_ENDS + 1, paginator.num_pages + 1)
-                ]
-            else:
-                page_range.extend(range(page_num + 1, paginator.num_pages + 1))
-
+    page_range = cl.paginator.get_elided_page_range(cl.page_num) if pagination_required else []
     need_show_all_link = cl.can_show_all and not cl.show_all and cl.multi_page
     return {
         'cl': cl,
diff --git a/django/core/paginator.py b/django/core/paginator.py
index ec0ebe0403..7db64913d9 100644
--- a/django/core/paginator.py
+++ b/django/core/paginator.py
@@ -25,6 +25,9 @@ class EmptyPage(InvalidPage):
 
 
 class Paginator:
+    # Translators: String used to replace omitted page numbers in elided page
+    # range generated by paginators, e.g. [1, 2, '…', 5, 6, 7, '…', 9, 10].
+    ELLIPSIS = _('…')
 
     def __init__(self, object_list, per_page, orphans=0,
                  allow_empty_first_page=True):
@@ -128,6 +131,37 @@ class Paginator:
                 stacklevel=3
             )
 
+    def get_elided_page_range(self, number=1, *, on_each_side=3, on_ends=2):
+        """
+        Return a 1-based range of pages with some values elided.
+
+        If the page range is larger than a given size, the whole range is not
+        provided and a compact form is returned instead, e.g. for a paginator
+        with 50 pages, if page 43 were the current page, the output, with the
+        default arguments, would be:
+
+            1, 2, …, 40, 41, 42, 43, 44, 45, 46, …, 49, 50.
+        """
+        number = self.validate_number(number)
+
+        if self.num_pages <= (on_each_side + on_ends) * 2:
+            yield from self.page_range
+            return
+
+        if number > (1 + on_each_side + on_ends) + 1:
+            yield from range(1, on_ends + 1)
+            yield self.ELLIPSIS
+            yield from range(number - on_each_side, number + 1)
+        else:
+            yield from range(1, number + 1)
+
+        if number < (self.num_pages - on_each_side - on_ends) - 1:
+            yield from range(number + 1, number + on_each_side + 1)
+            yield self.ELLIPSIS
+            yield from range(self.num_pages - on_ends + 1, self.num_pages + 1)
+        else:
+            yield from range(number + 1, self.num_pages + 1)
+
 
 class Page(collections.abc.Sequence):