History view pagination (#1277)

* Implement history_view pagination

Borrowed from Django's object_history.html

* Move pagination logic below the permission check

This avoids performing any database queries before we know that the user should be able to view data.

* Reworded the docs around changing the page size

A developer is more likely to look for the term page size.

---------

Author: jurrian

AUTHORS.rst

@@ -83,6 +83,7 @@ Authors
 - Jordon Wing  (`jordonwii <https://github.com/jordonwii>`_)
 - Josh Fyne
 - Josh Thomas (`joshuadavidthomas <https://github.com/joshuadavidthomas>`_)
+- Jurrian Tromp (`jurrian <https://github.com/jurrian>`_)
 - Keith Hackbarth
 - Kevin Foster
 - Kira (`kiraware <https://github.com/kiraware>`_)

CHANGES.rst

@@ -12,6 +12,7 @@ Unreleased
 - Updated all djangoproject.com links to reference the stable version (gh-1420)
 - Dropped support for Python 3.8, which reached end-of-life on 2024-10-07 (gh-1421)
 - Added support for Django 5.1 (gh-1388)
+- Added pagination to ``SimpleHistoryAdmin`` (gh-1277)
 
 3.7.0 (2024-05-29)
 ------------------

docs/admin.rst

@@ -49,7 +49,7 @@ By default, the history log displays one line per change containing
 
 You can add other columns (for example the object's status to see
 how it evolved) by adding a ``history_list_display`` array of fields to the
-admin class
+admin class.
 
 .. code-block:: python
 
@@ -62,6 +62,7 @@ admin class
         list_display = ["id", "name", "status"]
         history_list_display = ["status"]
         search_fields = ['name', 'user__username']
+        history_list_per_page = 100
 
     admin.site.register(Poll, PollHistoryAdmin)
     admin.site.register(Choice, SimpleHistoryAdmin)
@@ -70,6 +71,27 @@ admin class
 .. image:: screens/5_history_list_display.png
 
 
+Changing the page size in the admin history list view
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, the history list view of ``SimpleHistoryAdmin`` shows the last 100 records.
+You can change this by adding a `history_list_per_page` attribute to the admin class.
+
+
+.. code-block:: python
+
+    from django.contrib import admin
+    from simple_history.admin import SimpleHistoryAdmin
+    from .models import Poll
+
+
+    class PollHistoryAdmin(SimpleHistoryAdmin):
+        # history_list_per_page defaults to 100
+        history_list_per_page = 200
+
+    admin.site.register(Poll, PollHistoryAdmin)
+
+
 Customizing the History Admin Templates
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

simple_history/admin.py

@@ -7,8 +7,10 @@
 from django.contrib import admin
 from django.contrib.admin import helpers
 from django.contrib.admin.utils import unquote
+from django.contrib.admin.views.main import PAGE_VAR
 from django.contrib.auth import get_permission_codename, get_user_model
 from django.core.exceptions import PermissionDenied
+from django.core.paginator import Paginator
 from django.db.models import QuerySet
 from django.shortcuts import get_object_or_404, render
 from django.urls import re_path, reverse
@@ -31,6 +33,7 @@ class SimpleHistoryAdmin(admin.ModelAdmin):
     object_history_template = "simple_history/object_history.html"
     object_history_list_template = "simple_history/object_history_list.html"
     object_history_form_template = "simple_history/object_history_form.html"
+    history_list_per_page = 100
 
     def get_urls(self):
         """Returns the additional urls used by the Reversion admin."""
@@ -72,14 +75,19 @@ def history_view(self, request, object_id, extra_context=None):
         if not self.has_view_history_or_change_history_permission(request, obj):
             raise PermissionDenied
 
+        # Use the same pagination as in Django admin, with history_list_per_page items
+        paginator = Paginator(historical_records, self.history_list_per_page)
+        page_obj = paginator.get_page(request.GET.get(PAGE_VAR))
+        page_range = paginator.get_elided_page_range(page_obj.number)
+
         # Set attribute on each historical record from admin methods
         for history_list_entry in history_list_display:
             value_for_entry = getattr(self, history_list_entry, None)
             if value_for_entry and callable(value_for_entry):
-                for record in historical_records:
+                for record in page_obj.object_list:
                     setattr(record, history_list_entry, value_for_entry(record))
 
-        self.set_history_delta_changes(request, historical_records)
+        self.set_history_delta_changes(request, page_obj)
 
         content_type = self.content_type_model_cls.objects.get_for_model(
             get_user_model()
@@ -92,7 +100,10 @@ def history_view(self, request, object_id, extra_context=None):
         context = {
             "title": self.history_view_title(request, obj),
             "object_history_list_template": self.object_history_list_template,
-            "historical_records": historical_records,
+            "page_obj": page_obj,
+            "page_range": page_range,
+            "page_var": PAGE_VAR,
+            "pagination_required": paginator.count > self.history_list_per_page,
             "module_name": capfirst(force_str(opts.verbose_name_plural)),
             "object": obj,
             "root_path": getattr(self.admin_site, "root_path", None),

simple_history/templates/simple_history/object_history.html

@@ -7,7 +7,7 @@
     {% if not revert_disabled %}<p>
       {% blocktrans %}Choose a date from the list below to revert to a previous version of this object.{% endblocktrans %}</p>{% endif %}
     <div class="module">
-      {% if historical_records %}
+      {% if page_obj.object_list %}
         {% include object_history_list_template %}
       {% else %}
         <p>{% trans "This object doesn't have a change history." %}</p>

simple_history/templates/simple_history/object_history_list.html

@@ -18,7 +18,7 @@
     </tr>
   </thead>
   <tbody>
-    {% for record in historical_records %}
+    {% for record in page_obj %}
       <tr>
         <td>
           <a href="{% url opts|admin_urlname:'simple_history' object.pk record.pk %}">
@@ -65,3 +65,18 @@
     {% endfor %}
   </tbody>
 </table>
+
+<p class="paginator" style="border-top: 0">
+  {% if pagination_required %}
+    {% for i in page_range %}
+      {% if i == page_obj.paginator.ELLIPSIS %}
+        {{ page_obj.paginator.ELLIPSIS }}
+      {% elif i == page_obj.number %}
+        <span class="this-page">{{ i }}</span>
+      {% else %}
+        <a href="?{{ page_var }}={{ i }}" {% if i == page_obj.paginator.num_pages %} class="end" {% endif %}>{{ i }}</a>
+      {% endif %}
+    {% endfor %}
+  {% endif %}
+  {{ page_obj.paginator.count }} {% blocktranslate count counter=page_obj.paginator.count %}entry{% plural %}entries{% endblocktranslate %}
+</p>

simple_history/tests/tests/test_admin.py

@@ -4,6 +4,7 @@
 import django
 from django.contrib.admin import AdminSite
 from django.contrib.admin.utils import quote
+from django.contrib.admin.views.main import PAGE_VAR
 from django.contrib.auth import get_user_model
 from django.contrib.auth.models import Permission
 from django.contrib.messages.storage.fallback import FallbackStorage
@@ -556,6 +557,125 @@ def test_response_change(self):
 
         self.assertEqual(response["Location"], "/awesome/url/")
 
+    def test_history_view_pagination(self):
+        """
+        Ensure the history_view handles pagination correctly.
+        The default history_list_per_page is 100 so page 2 should have 1 record.
+        """
+        # Create a Poll object and make more than 100 changes to ensure pagination
+        poll = Poll.objects.create(question="what?", pub_date=today)
+        for i in range(100):
+            poll.question = f"change_{i}"
+            poll.save()
+
+        # Verify that there are 100+1 (initial creation) historical records
+        self.assertEqual(poll.history.count(), 101)
+
+        admin_site = AdminSite()
+        admin = SimpleHistoryAdmin(Poll, admin_site)
+
+        self.login(superuser=True)
+
+        # Simulate a request to the second page
+        request = RequestFactory().get("/", {PAGE_VAR: "2"})
+        request.user = self.user
+
+        # Patch the render function
+        with patch("simple_history.admin.render") as mock_render:
+            admin.history_view(request, str(poll.id))
+
+            # Ensure the render function was called
+            self.assertTrue(mock_render.called)
+
+            # Extract context passed to render function
+            action_list_count = len(mock_render.call_args[0][2]["page_obj"].object_list)
+
+            # Check if only 1 (101 - 100 from the first page)
+            # objects are present in the context
+            self.assertEqual(action_list_count, 1)
+
+    def test_history_view_pagination_no_pagination(self):
+        """
+        When all records fit on one page because the history_list_per_page is
+        higher than the number of records, ensure that the pagination is not set.
+        But it should show the number of entries.
+        """
+        # Create a Poll object and make more than 50 changes to ensure pagination
+        poll = Poll.objects.create(question="what?", pub_date=today)
+        for i in range(60):
+            poll.question = f"change_{i}"
+            poll.save()
+
+        # Verify that there are 60+1 (initial creation) historical records
+        self.assertEqual(poll.history.count(), 61)
+
+        # Create an admin with more per page than the number of records
+        class CustomSimpleHistoryAdmin(SimpleHistoryAdmin):
+            history_list_per_page = 200
+
+        admin_site = AdminSite()
+        admin = CustomSimpleHistoryAdmin(Poll, admin_site)
+
+        self.login(superuser=True)
+
+        # Simulate a request to the second page
+        request = RequestFactory().get("/", {PAGE_VAR: "2"})
+        request.user = self.user
+
+        response = admin.history_view(request, str(poll.id))
+
+        expected = '<p class="paginator" style="border-top: 0">61 entries</p>'
+        self.assertInHTML(expected, response.content.decode())
+
+    def test_history_view_pagination_last_page(self):
+        """
+        With 31 records, the last page should have 1 record. Non-existing pages
+        also end up on the last page.
+        """
+        # Create a Poll object and make more than 30 changes to ensure pagination
+        poll = Poll.objects.create(question="what?", pub_date=today)
+        for i in range(30):
+            poll.question = f"change_{i}"
+            poll.save()
+
+        expected_entry_count = 31
+
+        # Verify that there are 30+1 (initial creation) historical records
+        self.assertEqual(poll.history.count(), expected_entry_count)
+
+        # Create an admin with less per page than the number of records
+        class CustomSimpleHistoryAdmin(SimpleHistoryAdmin):
+            history_list_per_page = 10
+
+        admin_site = AdminSite()
+        admin = CustomSimpleHistoryAdmin(Poll, admin_site)
+
+        self.login(superuser=True)
+
+        # Simulate a request to the 4th and last page
+        request = RequestFactory().get("/", {PAGE_VAR: "4"})
+        request.user = self.user
+
+        response = admin.history_view(request, str(poll.id))
+
+        expected = (
+            '<p class="paginator" style="border-top: 0">'
+            '<a href="?p=1" >1</a>'
+            '<a href="?p=2" >2</a>'
+            '<a href="?p=3" >3</a>'
+            '<span class="this-page">4</span>'
+            f"{expected_entry_count} entries"
+            "</p>"
+        )
+        self.assertInHTML(expected, response.content.decode())
+
+        # Also a non-existent page should return the last page
+        request = RequestFactory().get("/", {PAGE_VAR: "5"})
+        request.user = self.user
+
+        response = admin.history_view(request, str(poll.id))
+        self.assertInHTML(expected, response.content.decode())
+
     def test_response_change_change_history_setting_off(self):
         """
         Test the response_change method that it works with a _change_history