Redirect to challenge landing pages when task templates don't exist

stade/core/templates/stats.html

@@ -90,7 +90,7 @@ <h4>Success/Total</h4>
                   </form>
                 {% endif %}
                 <li>
-                  <a href="{% if task.challenge.slug == 'milk10k' %}{% url 'challenge-landing' 'milk10k' %}{% else %}{% url 'task-landing' task.challenge.slug task.id %}{% endif %}">
+                  <a href="{% url 'task-landing' task.challenge.slug task.id %}">
                     <span>{{ task.name }}</span>
                   </a>
 

stade/core/views.py

@@ -8,7 +8,8 @@
 from django.contrib.auth.models import User
 from django.db.models import Count, Exists, OuterRef, Prefetch
 from django.http import Http404, HttpResponseRedirect
-from django.shortcuts import get_object_or_404, render
+from django.shortcuts import get_object_or_404, redirect, render
+from django.template.loader import TemplateDoesNotExist, get_template
 from django.urls import reverse
 from django.utils import timezone
 from django.views.decorators.http import require_http_methods
@@ -108,15 +109,15 @@ def leaderboard_page(request, challenge):
 def task_landing(request, challenge, task_id):
     task = get_object_or_404(Task.objects.filter(challenge=challenge), pk=task_id)
 
-    # The 2019 challenge doesn't have distinct task landing pages
-    if challenge.slug == '2019':
-        return challenge_landing(request, challenge)
+    template = f'landing/{challenge.slug}/{task_id}.html'
 
-    return render(
-        request,
-        f'landing/{challenge.slug}/{task_id}.html',
-        {'challenge': challenge, 'task': task},
-    )
+    # certain challenges don't have distinct task landing pages e.g. 2019 and MILK10k
+    try:
+        get_template(template)
+    except TemplateDoesNotExist:
+        return redirect(reverse('challenge-landing', args=[challenge.slug]))
+
+    return render(request, template, {'challenge': challenge, 'task': task})
 
 
 def challenge_landing(request, challenge):