Account for missing locked_at

wagtail/admin/templates/wagtailadmin/reports/listing/_list_unlock.html

@@ -7,23 +7,27 @@
     <td>
         {% page_permissions page as perms %}
         <p>
-            {% with page.locked_at|date:"d M Y H:i" as locking_date %}
-                {% if page.locked_by %}
-                    {% if page.locked_by_id == request.user.pk %}
-                        {% blocktrans %}
-                            Locked by <b>you</b> at <b>{{ locking_date }}</b>
-                        {% endblocktrans %}
+            {% if page.locked_at %}
+                {% with page.locked_at|date:"d M Y H:i" as locking_date %}
+                    {% if page.locked_by %}
+                        {% if page.locked_by_id == request.user.pk %}
+                            {% blocktrans %}
+                                Locked by <b>you</b> at <b>{{ locking_date }}</b>
+                            {% endblocktrans %}
+                        {% else %}
+                            {% blocktrans with locked_by=page.locked_by %}
+                                Locked by <b>{{ locked_by }}</b> at <b>{{ locking_date }}</b>
+                            {% endblocktrans %}
+                        {% endif %}
                     {% else %}
-                        {% blocktrans with locked_by=page.locked_by %}
-                            Locked by <b>{{ locked_by }}</b> at <b>{{ locking_date }}</b>
+                        {% blocktrans %}
+                            Locked at <b>{{ locking_date }}</b>
                         {% endblocktrans %}
                     {% endif %}
-                {% else %}
-                    {% blocktrans %}
-                        Locked at <b>{{ locking_date }}</b>
-                    {% endblocktrans %}
-                {% endif %}
-            {% endwith %}
+                {% endwith %}
+            {% else %}
+                {% trans 'Locked' %}
+            {% endif %}
         </p>
         {% if perms.can_unlock %}
             <form action="{% url 'wagtailadmin_pages:unlock' page.id %}" method="post">

wagtail/core/models.py

@@ -1833,6 +1833,30 @@ class UserPagePermissionsProxy:
         """Return True if the user has permission to publish any pages"""
         return self.publishable_pages().exists()
 
+    def unlockable_pages(self):
+        """Return a queryset of the pages that this user has permission to unlock"""
+        # Deal with the trivial cases first...
+        if not self.user.is_active:
+            return Page.objects.none()
+        if self.user.is_superuser:
+            return Page.objects.all()
+
+        unlockable_pages = Page.objects.none()
+
+        for perm in self.permissions.filter(permission_type='unlock'):
+            # user has publish permission on any subpage of perm.page
+            # (including perm.page itself)
+            unlockable_pages |= Page.objects.descendant_of(perm.page, inclusive=True)
+
+        pages_locked_by_user = Page.objects.filter(locked_by=self.user)
+        unlockable_pages |= pages_locked_by_user
+
+        return unlockable_pages
+
+    def can_unlock_pages(self):
+        """Return True if the user has permission to unlock any pages"""
+        return self.unlockable_pages().exists()
+
 
 class PagePermissionTester:
     def __init__(self, user_perms, page):