replaced removed .is_ajax method with request.headers.get('x-requested-with') == 'XMLHttpRequest'.

- https://docs.djangoproject.com/en/3.2/releases/3.1/#id2
> The HttpRequest.is_ajax() method is deprecated as it relied on a jQuery-specific way of signifying AJAX calls, while current usage tends to use the JavaScript Fetch API. Depending on your use case, you can either write your own AJAX detection method, or use the new HttpRequest.accepts() method if your code depends on the client Accept HTTP header.

wagtail/admin/auth.py

@@ -35,7 +35,7 @@ def users_with_page_permission(page, permission_type, include_superusers=True):
 
 def permission_denied(request):
     """Return a standard 'permission denied' response"""
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         raise PermissionDenied
 
     from wagtail.admin import messages
@@ -141,7 +141,7 @@ def user_has_any_page_permission(user):
 
 
 def reject_request(request):
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         raise PermissionDenied
 
     # import redirect_to_login here to avoid circular imports on model files that import
@@ -193,12 +193,12 @@ def require_admin_access(view_func):
                     return view_func(request, *args, **kwargs)
 
             except PermissionDenied:
-                if request.is_ajax():
+                if request.headers.get('x-requested-with') == 'XMLHttpRequest':
                     raise
 
                 return permission_denied(request)
 
-        if not request.is_ajax():
+        if not request.headers.get('x-requested-with') == 'XMLHttpRequest':
             messages.error(request, _('You do not have permission to access the admin'))
 
         return reject_request(request)

wagtail/admin/views/pages/search.py

@@ -93,7 +93,7 @@ def search(request):
     paginator = Paginator(pages, per_page=20)
     pages = paginator.get_page(request.GET.get('p'))
 
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         return TemplateResponse(request, "wagtailadmin/pages/search_results.html", {
             'pages': pages,
             'all_pages': all_pages,

wagtail/admin/views/pages/workflow.py

@@ -88,13 +88,13 @@ class WorkflowAction(BaseWorkflowFormView):
             form = self.form_class(request.POST)
             if form.is_valid():
                 redirect_to = self.task.on_action(self.task_state, request.user, self.action_name, **form.cleaned_data) or self.redirect_to
-            elif self.action_modal and request.is_ajax():
+            elif self.action_modal and request.headers.get('x-requested-with') == 'XMLHttpRequest':
                 # show form errors
                 return self.render_modal_form(request, form)
         else:
             redirect_to = self.task.on_action(self.task_state, request.user, self.action_name) or self.redirect_to
 
-        if request.is_ajax():
+        if request.headers.get('x-requested-with') == 'XMLHttpRequest':
             return render_modal_workflow(request, '', None, {}, json_data={'step': 'success', 'redirect': redirect_to})
         return redirect(redirect_to)
 
@@ -113,7 +113,7 @@ class CollectWorkflowActionData(BaseWorkflowFormView):
         form = self.form_class(request.POST)
         if form.is_valid():
             return render_modal_workflow(request, '', None, {}, json_data={'step': 'success', 'cleaned_data': form.cleaned_data})
-        elif self.action_modal and request.is_ajax():
+        elif self.action_modal and request.headers.get('x-requested-with') == 'XMLHttpRequest':
             # show form errors
             return self.render_modal_form(request, form)
 

wagtail/contrib/redirects/views.py

@@ -54,7 +54,7 @@ def index(request):
     redirects = paginator.get_page(request.GET.get('p'))
 
     # Render template
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         return TemplateResponse(request, "wagtailredirects/results.html", {
             'ordering': ordering,
             'redirects': redirects,

wagtail/contrib/search_promotions/views.py

@@ -48,7 +48,7 @@ def index(request):
     paginator = Paginator(queries, per_page=20)
     queries = paginator.get_page(request.GET.get('p'))
 
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         return TemplateResponse(request, "wagtailsearchpromotions/results.html", {
             'is_searching': is_searching,
             'ordering': ordering,

wagtail/core/models/__init__.py

@@ -1102,7 +1102,7 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
         return context
 
     def get_template(self, request, *args, **kwargs):
-        if request.is_ajax():
+        if request.headers.get('x-requested-with') == 'XMLHttpRequest':
             return self.ajax_template or self.template
         else:
             return self.template

wagtail/users/views/groups.py

@@ -61,7 +61,7 @@ class IndexView(mixins.SearchableListMixin, generic.IndexView):
     ordering = ['name']
 
     def get_template_names(self):
-        if self.request.is_ajax():
+        if self.request.headers.get('x-requested-with') == 'XMLHttpRequest':
             return ['wagtailusers/groups/results.html']
         else:
             return ['wagtailusers/groups/index.html']

wagtail/users/views/users.py

@@ -101,7 +101,7 @@ def index(request, *args):
     paginator = Paginator(users.select_related('wagtail_userprofile'), per_page=20)
     users = paginator.get_page(request.GET.get('p'))
 
-    if request.is_ajax():
+    if request.headers.get('x-requested-with') == 'XMLHttpRequest':
         return TemplateResponse(request, "wagtailusers/users/results.html", {
             'users': users,
             'is_searching': is_searching,