Fix git blame syntax highlighting when different commits break up lines

Closes #1521

6 files changed, 43 insertions, 9 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 7d7b8e0aef8..b18d50beab6 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -12,6 +12,7 @@ v 7.12.0 (unreleased)
   - Disable "New Issue" and "New Merge Request" buttons when features are disabled in project settings (Stan Hu)
   - Remove Rack Attack monkey patches and bump to version 4.3.0 (Stan Hu)
   - Fix clone URL losing selection after a single click in Safari and Chrome (Stan Hu)
+  - Fix git blame syntax highlighting when different commits break up lines (Stan Hu)
   - Allow to configure location of the `.gitlab_shell_secret` file. (Jakub Jirutka)
   - Disabled expansion of top/bottom blobs for new file diffs
   - Update Asciidoctor gem to version 1.5.2. (Jakub Jirutka)
diff --git a/Gemfile b/Gemfile
index 8eb1f04000c..26981f3e0a3 100644
--- a/Gemfile
+++ b/Gemfile
@@ -277,4 +277,4 @@ end
 gem "newrelic_rpm"
 
 gem 'octokit', '3.7.0'
-gem "rugments"
+gem "rugments", "~> 1.0.0.beta7"
diff --git a/Gemfile.lock b/Gemfile.lock
index 80e4a44c1da..7dbc3b4ffa9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -531,7 +531,7 @@ GEM
     rubyntlm (0.5.0)
     rubypants (0.2.0)
     rugged (0.22.2)
-    rugments (1.0.0.beta6)
+    rugments (1.0.0.beta7)
     safe_yaml (0.9.7)
     sanitize (2.1.0)
       nokogiri (>= 1.4.4)
@@ -781,7 +781,7 @@ DEPENDENCIES
   rqrcode-rails3
   rspec-rails (= 2.99)
   rubocop (= 0.28.0)
-  rugments
+  rugments (~> 1.0.0.beta7)
   sanitize (~> 2.0)
   sass-rails (~> 4.0.2)
   sdoc
diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index 9fe5f82f02f..50df3801703 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -1,6 +1,6 @@
 module BlobHelper
-  def highlight(blob_name, blob_content, nowrap = false)
-    formatter = Rugments::Formatters::HTML.new(
+  def highlight(blob_name, blob_content, nowrap: false, continue: false)
+    @formatter ||= Rugments::Formatters::HTML.new(
       nowrap: nowrap,
       cssclass: 'code highlight',
       lineanchors: true,
@@ -8,11 +8,11 @@ module BlobHelper
     )
 
     begin
-      lexer = Rugments::Lexer.guess(filename: blob_name, source: blob_content)
-      result = formatter.format(lexer.lex(blob_content)).html_safe
+      @lexer ||= Rugments::Lexer.guess(filename: blob_name, source: blob_content).new
+      result = @formatter.format(@lexer.lex(blob_content, continue: continue)).html_safe
     rescue
       lexer = Rugments::Lexers::PlainText
-      result = formatter.format(lexer.lex(blob_content)).html_safe
+      result = @formatter.format(lexer.lex(blob_content)).html_safe
     end
 
     result
diff --git a/app/views/projects/blame/show.html.haml b/app/views/projects/blame/show.html.haml
index 462f5b7afb0..8019c7f4569 100644
--- a/app/views/projects/blame/show.html.haml
+++ b/app/views/projects/blame/show.html.haml
@@ -32,5 +32,5 @@
                 %code
                   :erb
                     <% lines.each do |line| %>
-                      <%= highlight(@blob.name, line, true).html_safe %>
+                      <%= highlight(@blob.name, line, nowrap: true, continue: true).html_safe %>
                     <% end %>
diff --git a/spec/helpers/blob_helper_spec.rb b/spec/helpers/blob_helper_spec.rb
new file mode 100644
index 00000000000..e49e4e6d5d8
--- /dev/null
+++ b/spec/helpers/blob_helper_spec.rb
@@ -0,0 +1,33 @@
+require 'spec_helper'
+
+describe BlobHelper do
+  describe 'highlight' do
+    let(:blob_name) { 'test.lisp' }
+    let(:no_context_content) { ":type \"assem\"))" }
+    let(:blob_content) { "(make-pathname :defaults name\n#{no_context_content}" }
+    let(:split_content) { blob_content.split("\n") }
+
+    it 'should return plaintext for unknown lexer context' do
+      result = highlight(blob_name, no_context_content, nowrap: true, continue: false)
+      expect(result).to eq('<span id="LC1" class="line">:type &quot;assem&quot;))</span>')
+    end
+
+    it 'should highlight single block' do
+      expected = %Q[<span id="LC1" class="line"><span class="p">(</span><span class="nb">make-pathname</span> <span class="ss">:defaults</span> <span class="nv">name</span></span>
+<span id="LC2" class="line"><span class="ss">:type</span> <span class="s">&quot;assem&quot;</span><span class="p">))</span></span>]
+
+      expect(highlight(blob_name, blob_content, nowrap: true, continue: false)).to eq(expected)
+    end
+
+    it 'should highlight continued blocks' do
+      # Both lines have LC1 as ID since formatter doesn't support continue at the moment
+      expected = [
+        '<span id="LC1" class="line"><span class="p">(</span><span class="nb">make-pathname</span> <span class="ss">:defaults</span> <span class="nv">name</span></span>',
+        '<span id="LC1" class="line"><span class="ss">:type</span> <span class="s">&quot;assem&quot;</span><span class="p">))</span></span>'
+      ]
+
+      result = split_content.map{ |content| highlight(blob_name, content, nowrap: true, continue: true) }
+      expect(result).to eq(expected)
+    end
+  end
+end