Merge branch 'fix-relative-root-emoji-support' into 'master'

Fix emoji paths in relative root configurations

## What does this MR do?

If a site specifies a relative URL root, emoji files would omit the path from the URL, leading to lots of 404s.

## Are there points in the code the reviewer needs to double check?

At first, I tried to use `ActionView::Helpers::AssetUrlHelper.asset_url` since this is what it's intended to do. But this helper function is extremely slow, and it took minutes to generate the URLs for the hundreds of links needed for each emoji.

## Why was this MR needed?

Because emojis were broken in relative URL installations

## What are the relevant issue numbers?

#15642

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [X] Added for this feature/bug
  - [x] All builds are passing
- [X] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [X] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5027

lib/gitlab/award_emoji.rb

@@ -66,8 +66,17 @@ module Gitlab
     def self.urls
       @urls ||= begin
                   path = File.join(Rails.root, 'fixtures', 'emojis', 'digests.json')
+                  # Construct the full asset path ourselves because
+                  # ActionView::Helpers::AssetUrlHelper.asset_url is slow for hundreds
+                  # of entries since it has to do a lot of extra work (e.g. regexps).
                   prefix = Gitlab::Application.config.assets.prefix
                   digest = Gitlab::Application.config.assets.digest
+                  base =
+                    if defined?(Gitlab::Application.config.relative_url_root) && Gitlab::Application.config.relative_url_root
+                      Gitlab::Application.config.relative_url_root
+                    else
+                      ''
+                    end
 
                   JSON.parse(File.read(path)).map do |hash|
                     if digest
@@ -76,7 +85,7 @@ module Gitlab
                       fname = hash['unicode']
                     end
 
-                    { name: hash['name'], path: "#{prefix}/#{fname}.png" }
+                    { name: hash['name'], path: File.join(base, prefix, "#{fname}.png") }
                   end
                 end
     end

spec/lib/gitlab/award_emoji_spec.rb

@@ -2,6 +2,10 @@ require 'spec_helper'
 
 describe Gitlab::AwardEmoji do
   describe '.urls' do
+    after do
+      Gitlab::AwardEmoji.instance_variable_set(:@urls, nil)
+    end
+
     subject { Gitlab::AwardEmoji.urls }
 
     it { is_expected.to be_an_instance_of(Array) }
@@ -15,6 +19,17 @@ describe Gitlab::AwardEmoji do
         end
       end
     end
+
+    context 'handles relative root' do
+      it 'includes the full path' do
+        allow(Gitlab::Application.config).to receive(:relative_url_root).and_return('/gitlab')
+
+        subject.each do |hash|
+          expect(hash[:name]).to be_an_instance_of(String)
+          expect(hash[:path]).to start_with('/gitlab')
+        end
+      end
+    end
   end
 
   describe '.emoji_by_category' do