FEATURE: new category setting to add "Unassigned" navigation menu

When a category is used exclusively for managing topic assignments it can
be very useful to list all the unassigned topics. This introduces a new
category setting that allows admins to opt for this new navigation item.

It works both on mobile and desktop.

This uses an amended nav item API, to experience this fully you need latest
versions of Discourse.

assets/javascripts/discourse-assign/connectors/category-custom-settings/assign-settings.hbs

@@ -0,0 +1,13 @@
+<h3>{{i18n 'discourse_assign.assign.title'}}</h3>
+<section class='field'>
+  <div class="enable-accepted-answer">
+    <label class="checkbox-label">
+      {{input
+        type="checkbox"
+        checked=(readonly category.enable_unassigned_filter)
+        change=(action "onChangeSetting" value="target.checked")
+      }}
+      {{i18n 'discourse_assign.add_unassigned_filter'}}
+    </label>
+  </div>
+</section>

assets/javascripts/discourse-assign/connectors/category-custom-settings/assign-settings.js.es6

@@ -0,0 +1,10 @@
+export default {
+  actions: {
+    onChangeSetting(value) {
+      this.set(
+        "category.custom_fields.enable_unassigned_filter",
+        value ? "true" : "false"
+      );
+    }
+  }
+};

assets/javascripts/discourse-assign/initializers/extend-for-assigns.js.es6

@@ -55,6 +55,29 @@ function registerTopicFooterButtons(api) {
 }
 
 function initialize(api) {
+  api.addNavigationBarItem({
+    name: "unassigned",
+    customFilter: category => {
+      return category && category.enable_unassigned_filter;
+    },
+    customHref: category => {
+      if (category) {
+        return (
+          Discourse.getURL(category.url) +
+          "/l/latest?status=open&assigned=nobody"
+        );
+      }
+    },
+    forceActive: (category, args, router) => {
+      return (
+        router.currentURL &&
+        router.currentURL.indexOf("assigned=nobody") > -1 &&
+        router.currentURL.indexOf("status=open") > -1
+      );
+    },
+    before: "top"
+  });
+
   // You can't act on flags claimed by another user
   api.modifyClass(
     "component:flagged-post",

assets/javascripts/discourse-assign/pre-initializers/extend-category-for-assign.js.es6

@@ -0,0 +1,20 @@
+import Category from "discourse/models/category";
+
+export default {
+  name: "extend-category-for-assign",
+
+  before: "inject-discourse-objects",
+
+  initialize() {
+    Category.reopen({
+      enable_unassigned_filter: Ember.computed(
+        "custom_fields.enable_unassigned_filter",
+        {
+          get(fieldName) {
+            return Ember.get(this.custom_fields, fieldName) === "true";
+          }
+        }
+      )
+    });
+  }
+};

config/locales/client.en.yml

@@ -1,9 +1,14 @@
 en:
   js:
+    filters:
+      unassigned:
+        title: "Unassigned"
+        help: "Topics that are not assigned"
     action_codes:
       assigned: "assigned %{who} %{when}"
       unassigned: "unassigned %{who} %{when}"
     discourse_assign:
+      add_unassigned_filter: "Add 'unassigned' filter to category"
       cant_act: "You cannot act on flags that have been assigned to other users"
       cant_act_unclaimed: "You must claim this topic before acting on flags."
       assigned: "Assigned"

plugin.rb

@@ -100,6 +100,7 @@ after_initialize do
   end
 
   TopicList.preloaded_custom_fields << TopicAssigner::ASSIGNED_TO_ID
+  Site.preloaded_category_custom_fields << "enable_unassigned_filter" if Site.respond_to? :preloaded_category_custom_fields
 
   TopicList.on_preload do |topics, topic_list|
     if SiteSetting.assign_enabled?