Fix for the "0 available post types" case when clicking on the "Create Post" button

app/controllers/categories_controller.rb

@@ -127,9 +127,11 @@ def rss_feed
   end
 
   def post_types
-    @post_types = @category.post_types.where(is_top_level: true)
+    @post_types = @category.top_level_post_types
     if @post_types.one?
       redirect_to new_category_post_path(post_type: @post_types.first, category: @category)
+    elsif @post_types.empty? && current_user&.admin?
+      redirect_to edit_category_post_types_path(@category, no_return: '1')
     end
   end
 

app/models/category.rb

@@ -22,6 +22,10 @@ def public?
     trust_level <= 0
   end
 
+  def top_level_post_types
+    post_types.where(is_top_level: true)
+  end
+
   def new_posts_for?(user)
     key = "#{community_id}/#{user.id}/#{id}/last_visit"
     Rails.cache.fetch key, expires_in: 5.minutes do

app/views/categories/category_post_types.html.erb

@@ -1,8 +1,17 @@
-<p class="has-font-size-caption">
-  <%= link_to edit_category_path(@category) do %>
-    &laquo; Back to category edit
-  <% end %>
-</p>
+<%#
+    View for managing allowed category post types
+
+    Parameters:
+      params[:no_return] : whether to suppress the return link
+%>
+
+<% unless params[:no_return] == '1' %>
+  <p class="has-font-size-caption">
+    <%= link_to edit_category_path(@category) do %>
+      &laquo; Back to category edit
+    <% end %>
+  </p>
+<% end %>
 <h1>Allowed post types for <%= @category.name %></h1>
 <p class="has-font-size-caption">
   Only post types listed here are allowed to be posted in this category. Not all will be displayed as available options

app/views/categories/post_types.html.erb

@@ -1,6 +1,12 @@
-<h1>What kind of post?</h1>
+<% header_title = @post_types.any? ? 'What kind of post?' : 'No allowed post types'
+   header_subtitle = @post_types.any? \
+    ? 'This category has more than one type of post available. Pick a post type to get started.'
+    : 'This category does not have any post types available.' 
+%>
+
+<h1><%= header_title %></h1>
 <p class="has-font-size-larger has-color-tertiary-500">
-  This category has more than one type of post available. Pick a post type to get started.
+  <%= header_subtitle %>
 </p>
 
 <% @post_types.each do |pt| %>

app/views/layouts/_header.html.erb

@@ -282,9 +282,16 @@ $(() => {
             <% end %>
           <% end %>
           <div class="category-header--nav-separator"></div>
-          <%= link_to category_post_types_path(current_cat.id),
-                      class: 'category-header--nav-item is-button' do %>
-            <%= current_cat.button_text.present? ? current_cat.button_text : 'Create Post' %>
+          <% button_text = current_cat.button_text.present? ? current_cat.button_text : 'Create Post' %>
+          <% if current_cat&.top_level_post_types.any? || admin? %>
+            <%= link_to category_post_types_path(current_cat.id),
+                        class: "category-header--nav-item is-button" do %>
+              <%= button_text %>
+            <% end %>
+          <% else %>
+            <%= button_tag button_text, class: "button is-muted is-outlined",
+                                        disabled: true,
+                                        title: "The category doesn't have any allowed post types" %>
           <% end %>
         </div>
       </div>