Remove user_color_scheme_class

Instead of rendering this value server-side, we use Javascript and Gon
to apply the user's color scheme (or the default) to any syntax
highlighted code blocks.

This will make it easier to cache these blocks in the future because
they're no longer state-dependent.

app/assets/javascripts/syntax_highlight.coffee

@@ -0,0 +1,9 @@
+# Applies a syntax highlighting color scheme CSS class to any element with the
+# `js-syntax-highlight` class
+#
+# ### Example Markup
+#
+#   <div class="js-syntax-highlight"></div>
+#
+$(document).on 'ready page:load', ->
+  $('.js-syntax-highlight').addClass(gon.user_color_scheme)

app/controllers/application_controller.rb

@@ -190,11 +190,12 @@ class ApplicationController < ActionController::Base
   end
 
   def add_gon_variables
+    gon.api_version            = API::API.version
+    gon.default_avatar_url     = URI::join(Gitlab.config.gitlab.url, ActionController::Base.helpers.image_path('no_avatar.png')).to_s
     gon.default_issues_tracker = Project.new.default_issue_tracker.to_param
-    gon.api_version = API::API.version
-    gon.relative_url_root = Gitlab.config.gitlab.relative_url_root
-    gon.default_avatar_url = URI::join(Gitlab.config.gitlab.url, ActionController::Base.helpers.image_path('no_avatar.png')).to_s
-    gon.max_file_size = current_application_settings.max_attachment_size;
+    gon.max_file_size          = current_application_settings.max_attachment_size
+    gon.relative_url_root      = Gitlab.config.gitlab.relative_url_root
+    gon.user_color_scheme      = Gitlab::ColorSchemes.for_user(current_user).css_class
 
     if current_user
       gon.current_user_id = current_user.id

app/helpers/gitlab_markdown_helper.rb

@@ -58,7 +58,7 @@ module GitlabMarkdownHelper
       @options = options
 
       # see https://github.com/vmg/redcarpet#darling-i-packed-you-a-couple-renderers-for-lunch
-      rend = Redcarpet::Render::GitlabHTML.new(self, user_color_scheme_class, options)
+      rend = Redcarpet::Render::GitlabHTML.new(self, options)
 
       # see https://github.com/vmg/redcarpet#and-its-like-really-simple-to-use
       @markdown = Redcarpet::Markdown.new(rend, MARKDOWN_OPTIONS)

app/helpers/preferences_helper.rb

@@ -33,10 +33,6 @@ module PreferencesHelper
     Gitlab::Themes.by_id(current_user.try(:theme_id)).css_class
   end
 
-  def user_color_scheme_class
-    Gitlab::ColorSchemes.by_id(current_user.try(:color_scheme_id)).css_class
-  end
-
   def prefer_readme?
     !current_user ||
       current_user.project_view == 'readme'

app/views/search/results/_blob.html.haml

@@ -7,4 +7,4 @@
         %strong
           = blob.filename
     .file-content.code.term
-      = render 'shared/file_highlight', blob: blob, first_line_number: blob.startline, user_color_scheme_class: 'white'
+      = render 'shared/file_highlight', blob: blob, first_line_number: blob.startline

app/views/search/results/_snippet_blob.html.haml

@@ -23,7 +23,7 @@
                 .nothing-here-block Empty file
       - else
         .file-content.code
-          %div.highlighted-data{class: user_color_scheme_class}
+          %div.highlighted-data.js-syntax-highlight
             .line-numbers
               - snippet_blob[:snippet_chunks].each do |snippet|
                 - unless snippet[:data].empty?

app/views/search/results/_wiki_blob.html.haml

@@ -7,4 +7,4 @@
         %strong
           = wiki_blob.filename
     .file-content.code.term
-      = render 'shared/file_highlight', blob: wiki_blob, first_line_number: wiki_blob.startline, user_color_scheme_class: 'white'
+      = render 'shared/file_highlight', blob: wiki_blob, first_line_number: wiki_blob.startline

app/views/shared/_file_highlight.html.haml

@@ -1,4 +1,4 @@
-.file-content.code{class: user_color_scheme_class}
+.file-content.code.js-syntax-highlight
   .line-numbers
     - if blob.data.present?
       - blob.data.lines.each_index do |index|

lib/redcarpet/render/gitlab_html.rb

@@ -4,9 +4,8 @@ class Redcarpet::Render::GitlabHTML < Redcarpet::Render::HTML
   attr_reader :template
   alias_method :h, :template
 
-  def initialize(template, color_scheme, options = {})
+  def initialize(template, options = {})
     @template = template
-    @color_scheme = color_scheme
     @options = options.dup
 
     @options.reverse_merge!(
@@ -35,7 +34,7 @@ class Redcarpet::Render::GitlabHTML < Redcarpet::Render::HTML
     end
 
     formatter = Rouge::Formatters::HTMLGitlab.new(
-      cssclass: "code highlight #{@color_scheme} #{lexer.tag}"
+      cssclass: "code highlight js-syntax-highlight #{lexer.tag}"
     )
     formatter.format(lexer.lex(code))
   end

spec/features/markdown_spec.rb

@@ -224,8 +224,4 @@ describe 'GitLab Markdown', feature: true do
   def current_user
     @feat.user
   end
-
-  def user_color_scheme_class
-    :white
-  end
 end

spec/helpers/preferences_helper_spec.rb

@@ -48,25 +48,4 @@ describe PreferencesHelper do
       ]
     end
   end
-
-  describe 'user_color_scheme_class' do
-    context 'with current_user is nil' do
-      it 'should return a string' do
-        allow(self).to receive(:current_user).and_return(nil)
-        expect(user_color_scheme_class).to be_kind_of(String)
-      end
-    end
-
-    context 'with a current_user' do
-      (1..5).each do |color_scheme_id|
-        context "with color_scheme_id == #{color_scheme_id}" do
-          it 'should return a string' do
-            current_user = double(color_scheme_id: color_scheme_id)
-            allow(self).to receive(:current_user).and_return(current_user)
-            expect(user_color_scheme_class).to be_kind_of(String)
-          end
-        end
-      end
-    end
-  end
 end