Make the preview view hack the title/tree fields to match the control page, in the same way that the frontend hook does

Author: gasman

experiments/admin_urls.py

@@ -6,5 +6,5 @@
 urlpatterns = [
     url(r'^experiment/report/(\d+)/$', views.experiment_report, name='report'),
     url(r'^experiment/select_winner/(\d+)/(\d+)/$', views.select_winner, name='select_winner'),
-    url(r'^experiment/report/preview/(\d+)/$', views.preview_for_report, name='preview_for_report'),
+    url(r'^experiment/report/preview/(\d+)/(\d+)/$', views.preview_for_report, name='preview_for_report'),
 ]

experiments/templates/experiments/report.html

@@ -39,7 +39,7 @@
                                     {% trans 'Use this' %}
                                 </button>
                                 <a class="button button-small button-primary" title="{% trans 'Preview' %}"
-                                   href="{% url 'experiments:preview_for_report' variation.pk %}">
+                                   href="{% url 'experiments:preview_for_report' experiment.pk variation.pk %}">
                                     <span class="icon icon-view"></span>
                                 </a>
                             </form>

experiments/utils.py

@@ -12,3 +12,13 @@ def percentage(fraction, population):
         return float(fraction) / float(population) * 100
     except (ValueError, ZeroDivisionError, TypeError):
         return 0.0
+
+
+def impersonate_other_page(page, other):
+    """Modify the title and tree location data of `page` to resemble `other`"""
+    page.id = other.id
+    page.pk = other.pk
+    page.path = other.path
+    page.depth = other.depth
+    page.url_path = other.url_path
+    page.title = other.title

experiments/views.py

@@ -9,7 +9,7 @@
 from wagtail.wagtailcore.models import Page
 
 from .models import Experiment, get_backend
-from .utils import get_user_id, percentage
+from .utils import get_user_id, impersonate_other_page, percentage
 
 
 def record_completion(request, slug):
@@ -69,11 +69,15 @@ def select_winner(request, experiment_id, variation_id):
     return redirect('experiments:report', experiment.pk)
 
 
-def preview_for_report(request, page_id):
+def preview_for_report(request, experiment_id, page_id):
+    experiment = get_object_or_404(Experiment, pk=experiment_id)
     page = get_object_or_404(Page, id=page_id).specific
     if not page.permissions_for_user(request.user).can_publish():
         raise PermissionDenied
 
+    # hack the title and page-tree-related fields to match the control page
+    impersonate_other_page(page, experiment.control_page)
+
     # pass in the real user request rather than page.dummy_request(), so that request.user
     # and request.revision_id will be picked up by the wagtail user bar
     return page.serve_preview(request, page.default_preview_mode)

experiments/wagtail_hooks.py

@@ -10,7 +10,7 @@
 from wagtail.wagtailcore import hooks
 
 from .models import Experiment
-from .utils import get_user_id
+from .utils import get_user_id, impersonate_other_page
 
 
 @hooks.register('register_admin_urls')
@@ -80,11 +80,6 @@ def check_experiments(page, request, serve_args, serve_kwargs):
             variation = variation.specific
 
             # hack the title and page-tree-related fields to match the control page
-            variation.id = page.id
-            variation.pk = page.pk
-            variation.path = page.path
-            variation.depth = page.depth
-            variation.url_path = page.url_path
-            variation.title = page.title
+            impersonate_other_page(variation, page)
 
             return variation.serve(request, *serve_args, **serve_kwargs)

tests/tests.py

@@ -297,6 +297,9 @@ def test_select_winner(self):
 
     def test_preview(self):
         response = self.client.get(
-            '/admin/experiments/experiment/report/preview/%d/' % self.homepage_alternative_1.pk
+            '/admin/experiments/experiment/report/preview/%d/%d/' % (
+                self.experiment.pk, self.homepage_alternative_1.pk
+            )
         )
         self.assertEqual(response.status_code, 200)
+        self.assertContains(response, "<title>Home</title>")