Decouple Gitlab::Markdown from the GitlabMarkdownHelper

This module is now the sole source of knowledge for *how* we render
Markdown (and GFM).

3 files changed, 94 insertions, 14 deletions

diff --git a/lib/gitlab/markdown.rb b/lib/gitlab/markdown.rb
index 9f6e19a09fd..de1da31a390 100644
--- a/lib/gitlab/markdown.rb
+++ b/lib/gitlab/markdown.rb
@@ -5,6 +5,44 @@ module Gitlab
   #
   # See the files in `lib/gitlab/markdown/` for specific processing information.
   module Markdown
+    # https://github.com/vmg/redcarpet#and-its-like-really-simple-to-use
+    REDCARPET_OPTIONS = {
+      no_intra_emphasis:   true,
+      tables:              true,
+      fenced_code_blocks:  true,
+      strikethrough:       true,
+      lax_spacing:         true,
+      space_after_headers: true,
+      superscript:         true,
+      footnotes:           true
+    }.freeze
+
+    # Convert a Markdown String into an HTML-safe String of HTML
+    #
+    # markdown - Markdown String
+    # context  - Hash of context options passed to our HTML Pipeline
+    #
+    # Returns an HTML-safe String
+    def self.render(markdown, context = {})
+      html = renderer.render(markdown)
+      html = gfm(html, context)
+
+      html.html_safe
+    end
+
+    # Convert a Markdown String into HTML without going through the HTML
+    # Pipeline.
+    #
+    # Note that because the pipeline is skipped, SanitizationFilter is as well.
+    # Do not output the result of this method to the user.
+    #
+    # markdown - Markdown String
+    #
+    # Returns a String
+    def self.render_without_gfm(markdown)
+      self.renderer.render(markdown)
+    end
+
     # Provide autoload paths for filters to prevent a circular dependency error
     autoload :AutolinkFilter,               'gitlab/markdown/autolink_filter'
     autoload :CommitRangeReferenceFilter,   'gitlab/markdown/commit_range_reference_filter'
@@ -18,6 +56,7 @@ module Gitlab
     autoload :RelativeLinkFilter,           'gitlab/markdown/relative_link_filter'
     autoload :SanitizationFilter,           'gitlab/markdown/sanitization_filter'
     autoload :SnippetReferenceFilter,       'gitlab/markdown/snippet_reference_filter'
+    autoload :SyntaxHighlightFilter,        'gitlab/markdown/syntax_highlight_filter'
     autoload :TableOfContentsFilter,        'gitlab/markdown/table_of_contents_filter'
     autoload :TaskListFilter,               'gitlab/markdown/task_list_filter'
     autoload :UserReferenceFilter,          'gitlab/markdown/user_reference_filter'
@@ -29,7 +68,7 @@ module Gitlab
     #                :xhtml               - output XHTML instead of HTML
     #                :reference_only_path - Use relative path for reference links
     # html_options - extra options for the reference links as given to link_to
-    def gfm(text, options = {}, html_options = {})
+    def self.gfm(text, options = {})
       return text if text.nil?
 
       # Duplicate the string so we don't alter the original, then call to_str
@@ -40,8 +79,8 @@ module Gitlab
       options.reverse_merge!(
         xhtml:                false,
         reference_only_path:  true,
-        project:              @project,
-        current_user:         current_user
+        project:              options[:project],
+        current_user:         options[:current_user]
       )
 
       @pipeline ||= HTML::Pipeline.new(filters)
@@ -61,12 +100,11 @@ module Gitlab
         current_user:    options[:current_user],
         only_path:       options[:reference_only_path],
         project:         options[:project],
-        reference_class: html_options[:class],
 
         # RelativeLinkFilter
-        ref:            @ref,
-        requested_path: @path,
-        project_wiki:   @project_wiki
+        ref:            options[:ref],
+        requested_path: options[:path],
+        project_wiki:   options[:project_wiki]
       }
 
       result = @pipeline.call(text, context)
@@ -83,14 +121,22 @@ module Gitlab
 
     private
 
+    def self.renderer
+      @markdown ||= begin
+        renderer = Redcarpet::Render::HTML.new
+        Redcarpet::Markdown.new(renderer, REDCARPET_OPTIONS)
+      end
+    end
+
     # Filters used in our pipeline
     #
     # SanitizationFilter should come first so that all generated reference HTML
     # goes through untouched.
     #
     # See https://github.com/jch/html-pipeline#filters for more filters.
-    def filters
+    def self.filters
       [
+        Gitlab::Markdown::SyntaxHighlightFilter,
         Gitlab::Markdown::SanitizationFilter,
 
         Gitlab::Markdown::RelativeLinkFilter,
diff --git a/lib/gitlab/markdown/syntax_highlight_filter.rb b/lib/gitlab/markdown/syntax_highlight_filter.rb
new file mode 100644
index 00000000000..9f468f98aeb
--- /dev/null
+++ b/lib/gitlab/markdown/syntax_highlight_filter.rb
@@ -0,0 +1,38 @@
+require 'html/pipeline/filter'
+require 'rouge/plugins/redcarpet'
+
+module Gitlab
+  module Markdown
+    # HTML Filter to highlight fenced code blocks
+    #
+    class SyntaxHighlightFilter < HTML::Pipeline::Filter
+      include Rouge::Plugins::Redcarpet
+
+      def call
+        doc.search('pre > code').each do |node|
+          highlight_node(node)
+        end
+
+        doc
+      end
+
+      def highlight_node(node)
+        language = node.attr('class')
+        code     = node.text
+
+        highlighted = block_code(code, language)
+
+        # Replace the parent `pre` element with the entire highlighted block
+        node.parent.replace(highlighted)
+      end
+
+      private
+
+      # Override Rouge::Plugins::Redcarpet#rouge_formatter
+      def rouge_formatter(lexer)
+        Rouge::Formatters::HTMLGitlab.new(
+          cssclass: "code highlight js-syntax-highlight #{lexer.tag}")
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/reference_extractor.rb b/lib/gitlab/reference_extractor.rb
index e836b05ff25..20f4098057c 100644
--- a/lib/gitlab/reference_extractor.rb
+++ b/lib/gitlab/reference_extractor.rb
@@ -10,7 +10,7 @@ module Gitlab
 
     def analyze(text)
       references.clear
-      @text = markdown.render(text.dup)
+      @text = Gitlab::Markdown.render_without_gfm(text)
     end
 
     %i(user label issue merge_request snippet commit commit_range).each do |type|
@@ -21,10 +21,6 @@ module Gitlab
 
     private
 
-    def markdown
-      @markdown ||= Redcarpet::Markdown.new(Redcarpet::Render::HTML, GitlabMarkdownHelper::MARKDOWN_OPTIONS)
-    end
-
     def references
       @references ||= Hash.new do |references, type|
         type = type.to_sym
@@ -42,7 +38,7 @@ module Gitlab
     # Returns the results Array for the requested filter type
     def pipeline_result(filter_type)
       klass  = filter_type.to_s.camelize + 'ReferenceFilter'
-      filter = "Gitlab::Markdown::#{klass}".constantize
+      filter = Gitlab::Markdown.const_get(klass)
 
       context = {
         project: project,