Show confirmation message before delete

wagtail/wagtailforms/templates/wagtailforms/confirm_delete.html

@@ -0,0 +1,19 @@
+{% extends "wagtailadmin/base.html" %}
+{% load i18n %}
+{% block titletag %}{% blocktrans with title=page.title %}Delete {{ title }}{% endblocktrans %}{% endblock %}
+{% block bodyclass %}menu-explorer{% endblock %}
+
+{% block content %}
+    {% trans "Delete" as del_str %}
+    {% include "wagtailadmin/shared/header.html" with title=del_str subtitle=page.title icon="doc-empty-inverse" %}
+
+    <div class="nice-padding">
+        <p>
+            {% trans 'Are you sure you want to delete this form submission?' %}
+        </p>
+        <form action="{% url 'wagtailforms_delete_submission' page.id submission.id %}" method="POST">
+            {% csrf_token %}
+            <input type="submit" value="{% trans 'Delete it' %}" class="serious">
+        </form>
+    </div>
+{% endblock %}

wagtail/wagtailforms/views.py

@@ -7,11 +7,11 @@ from django.core.exceptions import PermissionDenied
 from django.http import HttpResponse
 from django.shortcuts import get_object_or_404, render, redirect
 from django.utils.encoding import smart_str
-
+from django.utils.translation import ugettext as _
 from wagtail.wagtailcore.models import Page
 from wagtail.wagtailforms.models import FormSubmission, get_forms_for_user
 from wagtail.wagtailforms.forms import SelectDateForm
-
+from wagtail.wagtailadmin import messages
 
 def index(request):
     p = request.GET.get("p", 1)
@@ -34,9 +34,20 @@ def index(request):
 def delete_submission(request, page_id, submission_id):
     if not get_forms_for_user(request.user).filter(id=page_id).exists():
         raise PermissionDenied
-    FormSubmission.objects.get(id=submission_id).delete()
 
-    return redirect('wagtailforms_list_submissions', page_id)
+    submission = get_object_or_404(FormSubmission, id=submission_id)
+    page = get_object_or_404(Page, id=page_id)
+
+    if request.method == 'POST':
+        submission.delete()
+
+        messages.success(request, _("Submission deleted."))
+        return redirect('wagtailforms_list_submissions', page_id)
+
+    return render(request, 'wagtailforms/confirm_delete.html', {
+        'page': page,
+        'submission': submission
+    })
 
 def list_submissions(request, page_id):
     form_page = get_object_or_404(Page, id=page_id).specific