expand the 'advanced' tab in case of server-side validation error

django/allgo/main/forms.py

@@ -142,6 +142,8 @@ class WebappForm(forms.ModelForm):
             widget=forms.RadioSelect)
 
     # Advanced
+    ADVANCED_FIELDS = ("docker_os", "memory_limit_mb", "job_queue",
+            "entrypoint", "owner", "tags")
     docker_os = forms.ModelChoiceField(
             queryset=DockerOs.objects.all().distinct(),
             label='Operating sytem',

django/allgo/main/views.py

@@ -227,6 +227,11 @@ class WebappUpdate(SuccessMessageMixin, LoginRequiredMixin, UpdateView):
     def get_context_data(self, **kwargs):
         ctx=super().get_context_data(**kwargs)
         ctx["action"] = "Update"
+
+        # we expand the 'advanced' tab if any of its field has a validation error
+        ctx["show_advanced"] = bool(set(ctx["form"].errors)
+                .intersection(ctx["form"].ADVANCED_FIELDS))
+
         return ctx
 
     def get_form(self):
@@ -287,6 +292,7 @@ class WebappCreate(SuccessMessageMixin, LoginRequiredMixin, IsProviderMixin, Cre
     def get_context_data(self, **kwargs):
         ctx=super().get_context_data(**kwargs)
         ctx["action"] = "Create"
+        ctx["show_advanced"] = False
         return ctx
 
     def form_valid(self, form):

django/allgo/templates/webapp_add_update.html

@@ -66,12 +66,12 @@
       <div class="card">
         <div class="card-header">
           <h5 class="mb-0">
-            <button class="btn btn-link" type="button" data-toggle="collapse" data-target="#collapseAdvanced" aria-expanded="false" aria-controls="collapseAdvanced">
+            <button class="btn btn-link" type="button" data-toggle="collapse" data-target="#collapseAdvanced" aria-expanded="{{show_advanced}}" aria-controls="collapseAdvanced">
               Advanced options
             </button>
           </h5>
         </div>
-        <div class="collapse" id="collapseAdvanced">
+        <div class="collapse {% if show_advanced %}show{% endif %}" id="collapseAdvanced">
           <div class="card-body">
             <div class="form-row">