FIX: If a group is unmentionable, don't render it as mentionable

Now if a group is visible but unmentionable, users can search for it
when composing by typing with `@`, but it will be rendered without the
grey background color.

It will also no longer pop up a JIT warning saying "You are about to
mention X people" because the group will not be mentioned.

app/assets/javascripts/discourse/lib/link-mentions.js.es6

@@ -51,6 +51,8 @@ function updateFound($mentions, usernames) {
           group: true,
           mentionable: mentionableGroups[username]
         });
+      } else if (foundGroups[username]) {
+        replaceSpan($e, username, { group: true });
       } else if (checked[username]) {
         $e.addClass("mention-tested");
       }

app/assets/stylesheets/common/base/topic-post.scss

@@ -760,12 +760,15 @@ blockquote > *:last-child {
 
 a.mention,
 a.mention-group {
-  padding: 2px 4px;
-  color: dark-light-choose($primary-high, $secondary-low);
-  background: $primary-low;
-  border-radius: 8px;
   font-weight: bold;
   font-size: 0.93em;
+  color: $primary;
+  &.notify {
+    color: dark-light-choose($primary-high, $secondary-low);
+    padding: 2px 4px;
+    background: $primary-low;
+    border-radius: 8px;
+  }
 }
 
 .popup-menu {

app/controllers/users_controller.rb

@@ -308,7 +308,7 @@ class UsersController < ApplicationController
     groups = Group.where(name: usernames).pluck(:name)
     mentionable_groups =
       if current_user
-        Group.mentionable(current_user)
+        Group.mentionable(current_user, include_public: false)
           .where(name: usernames)
           .pluck(:name, :user_count)
           .map do |name, user_count|

spec/requests/users_controller_spec.rb

@@ -2402,7 +2402,10 @@ describe UsersController do
 
   describe '#is_local_username' do
     fab!(:user) { Fabricate(:user) }
-    fab!(:group) { Fabricate(:group, name: "Discourse") }
+    fab!(:group) { Fabricate(:group, name: "Discourse", mentionable_level: Group::ALIAS_LEVELS[:everyone]) }
+    let(:unmentionable) {
+      Fabricate(:group, name: "Unmentionable", mentionable_level: Group::ALIAS_LEVELS[:nobody])
+    }
     fab!(:topic) { Fabricate(:topic) }
     fab!(:allowed_user) { Fabricate(:user) }
     let(:private_topic) { Fabricate(:private_message_topic, user: allowed_user) }
@@ -2416,11 +2419,21 @@ describe UsersController do
     end
 
     it "finds the group" do
+      sign_in(user)
       get "/u/is_local_username.json", params: { username: group.name }
-
       expect(response.status).to eq(200)
       json = JSON.parse(response.body)
-      expect(json["valid_groups"][0]).to eq(group.name)
+      expect(json["valid_groups"]).to include(group.name)
+      expect(json["mentionable_groups"].find { |g| g['name'] == group.name }).to be_present
+    end
+
+    it "finds unmentionable groups" do
+      sign_in(user)
+      get "/u/is_local_username.json", params: { username: unmentionable.name }
+      expect(response.status).to eq(200)
+      json = JSON.parse(response.body)
+      expect(json["valid_groups"]).to include(unmentionable.name)
+      expect(json["mentionable_groups"]).to be_blank
     end
 
     it "supports multiples usernames" do

test/javascripts/lib/link-mentions-test.js.es6

@@ -55,7 +55,7 @@ QUnit.test("linkSeenMentions replaces users and groups", async assert => {
   });
 
   assert.equal($("a", $root)[0].text, "@valid_user");
-  assert.equal($("a", $root)[1].text, "@mentionable_group");
+  assert.equal($("a", $root)[1].text, "@valid_group");
+  assert.equal($("a.notify", $root).text(), "@mentionable_group");
   assert.equal($("span.mention", $root)[0].innerHTML, "@invalid");
-  assert.equal($("span.mention", $root)[1].innerHTML, "@valid_group");
 });