FIX: `Group#mentionable` and `Group#messageable` not fully working.

app/assets/javascripts/discourse/components/composer-editor.js.es6

@@ -85,7 +85,11 @@ export default Ember.Component.extend({
     const $input = this.$('.d-editor-input');
     $input.autocomplete({
       template: findRawTemplate('user-selector-autocomplete'),
-      dataSource: term => userSearch({ term, topicId, includeGroups: true }),
+      dataSource: term => userSearch({
+        term,
+        topicId,
+        includeMentionableGroups: true
+      }),
       key: "@",
       transformComplete: v => v.username || v.name
     });

app/assets/javascripts/discourse/controllers/group.js.es6

@@ -48,9 +48,9 @@ export default Ember.Controller.extend({
     };
   },
 
-  @computed("model.mentionable")
-  displayGroupMessageButton(mentionable) {
-    return this.currentUser && mentionable;
+  @computed("model.messageable")
+  displayGroupMessageButton(messageable) {
+    return this.currentUser && messageable;
   },
 
   @observes('model.user_count')

app/serializers/group_show_serializer.rb

@@ -1,5 +1,5 @@
 class GroupShowSerializer < BasicGroupSerializer
-  attributes :is_group_user, :is_group_owner, :mentionable
+  attributes :is_group_user, :is_group_owner, :mentionable, :messageable
 
   def include_is_group_user?
     authenticated?
@@ -21,6 +21,10 @@ class GroupShowSerializer < BasicGroupSerializer
     authenticated?
   end
 
+  def include_messageable?
+    authenticated?
+  end
+
   def mentionable
     Group.mentionable(scope.user).exists?(id: object.id)
   end

test/javascripts/acceptance/groups-test.js.es6

@@ -132,7 +132,7 @@ QUnit.test("Admin Viewing Group", assert => {
   andThen(() => {
     assert.ok(find(".nav-pills li a[title='Edit Group']").length === 1, 'it should show edit group tab if user is admin');
     assert.ok(find(".nav-pills li a[title='Logs']").length === 1, 'it should show Logs tab if user is admin');
-
+    assert.equal(count('.group-message-button'), 1, 'it displays show group message button');
     assert.equal(find('.group-info-name').text(), 'Awesome Team', 'it should display the group name');
   });
 

test/javascripts/fixtures/group-fixtures.js.es6

@@ -12,7 +12,8 @@ export default {
       "public_exit":true,
       "flair_url": 'fa-adjust',
       "is_group_owner":true,
-      "mentionable":true
+      "mentionable":true,
+      "messageable":true
     }
   },
   "/groups/discourse/counts.json":{