Merge branch 'add-language-param-to-highlight' into 'master'

Add language param to highlight

See merge request gitlab-org/gitlab-ce!21584

28 files changed, 289 insertions, 125 deletions

diff --git a/app/controllers/admin/application_settings_controller.rb b/app/controllers/admin/application_settings_controller.rb
index 8040a14ef56..8f683ca06ad 100644
--- a/app/controllers/admin/application_settings_controller.rb
+++ b/app/controllers/admin/application_settings_controller.rb
@@ -61,7 +61,7 @@ class Admin::ApplicationSettingsController < Admin::ApplicationController
       format.html do
         usage_data_json = JSON.pretty_generate(Gitlab::UsageData.data)
 
-        render html: Gitlab::Highlight.highlight('payload.json', usage_data_json)
+        render html: Gitlab::Highlight.highlight('payload.json', usage_data_json, language: 'json')
       end
       format.json { render json: Gitlab::UsageData.to_json }
     end
diff --git a/app/controllers/projects/blob_controller.rb b/app/controllers/projects/blob_controller.rb
index 56a884b8a2a..c02ec407262 100644
--- a/app/controllers/projects/blob_controller.rb
+++ b/app/controllers/projects/blob_controller.rb
@@ -92,7 +92,7 @@ class Projects::BlobController < Projects::ApplicationController
     apply_diff_view_cookie!
 
     @blob.load_all_data!
-    @lines = Gitlab::Highlight.highlight(@blob.path, @blob.data, repository: @repository).lines
+    @lines = @blob.present.highlight.lines
 
     @form = UnfoldForm.new(params)
 
diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index ff7f1e3a9aa..638744a1426 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 module BlobHelper
-  def highlight(blob_name, blob_content, repository: nil, plain: false)
-    plain ||= blob_content.length > Blob::MAXIMUM_TEXT_HIGHLIGHT_SIZE
-    highlighted = Gitlab::Highlight.highlight(blob_name, blob_content, plain: plain, repository: repository)
+  def highlight(file_name, file_content, language: nil, plain: false)
+    highlighted = Gitlab::Highlight.highlight(file_name, file_content, plain: plain, language: language)
 
     raw %(<pre class="code highlight"><code>#{highlighted}</code></pre>)
   end
diff --git a/app/models/blob.rb b/app/models/blob.rb
index 31a839274b5..4f310e70f4f 100644
--- a/app/models/blob.rb
+++ b/app/models/blob.rb
@@ -1,12 +1,13 @@
 # frozen_string_literal: true
 
-# Blob is a Rails-specific wrapper around Gitlab::Git::Blob objects
+# Blob is a Rails-specific wrapper around Gitlab::Git::Blob, SnippetBlob and Ci::ArtifactBlob
 class Blob < SimpleDelegator
+  include Presentable
+  include BlobLanguageFromGitAttributes
+
   CACHE_TIME = 60 # Cache raw blobs referred to by a (mutable) ref for 1 minute
   CACHE_TIME_IMMUTABLE = 3600 # Cache blobs referred to by an immutable reference for 1 hour
 
-  MAXIMUM_TEXT_HIGHLIGHT_SIZE = 1.megabyte
-
   # Finding a viewer for a blob happens based only on extension and whether the
   # blob is binary or text, which means 1 blob should only be matched by 1 viewer,
   # and the order of these viewers doesn't really matter.
@@ -121,10 +122,6 @@ class Blob < SimpleDelegator
     end
   end
 
-  def no_highlighting?
-    raw_size && raw_size > MAXIMUM_TEXT_HIGHLIGHT_SIZE
-  end
-
   def empty?
     raw_size == 0
   end
diff --git a/app/models/concerns/blob_language_from_git_attributes.rb b/app/models/concerns/blob_language_from_git_attributes.rb
new file mode 100644
index 00000000000..70213d22147
--- /dev/null
+++ b/app/models/concerns/blob_language_from_git_attributes.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+# Applicable for blob classes with project attribute
+module BlobLanguageFromGitAttributes
+  extend ActiveSupport::Concern
+
+  def language_from_gitattributes
+    return nil unless project
+
+    repository = project.repository
+    repository.gitattribute(path, 'gitlab-language')
+  end
+end
diff --git a/app/presenters/blob_presenter.rb b/app/presenters/blob_presenter.rb
new file mode 100644
index 00000000000..6323c1b3389
--- /dev/null
+++ b/app/presenters/blob_presenter.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class BlobPresenter < Gitlab::View::Presenter::Simple
+  presents :blob
+
+  def highlight(plain: nil)
+    blob.load_all_data! if blob.respond_to?(:load_all_data!)
+
+    Gitlab::Highlight.highlight(
+      blob.path,
+      blob.data,
+      language: blob.language_from_gitattributes,
+      plain: plain
+    )
+  end
+end
diff --git a/app/views/projects/blob/viewers/_highlight_embed.html.haml b/app/views/projects/blob/viewers/_highlight_embed.html.haml
index 9bd4ef6ad0b..6a631fef1a9 100644
--- a/app/views/projects/blob/viewers/_highlight_embed.html.haml
+++ b/app/views/projects/blob/viewers/_highlight_embed.html.haml
@@ -4,4 +4,6 @@
       - blob.data.each_line.each_with_index do |_, index|
         %span.diff-line-num= index + 1
   .blob-content{ data: { blob_id: blob.id } }
-    = highlight(blob.path, blob.data, repository: nil, plain: blob.no_highlighting?)
+    %pre.code.highlight
+      %code
+        = blob.present.highlight
diff --git a/app/views/projects/blob/viewers/_text.html.haml b/app/views/projects/blob/viewers/_text.html.haml
index a91df321ca0..26ad23da436 100644
--- a/app/views/projects/blob/viewers/_text.html.haml
+++ b/app/views/projects/blob/viewers/_text.html.haml
@@ -1 +1 @@
-= render 'shared/file_highlight', blob: viewer.blob, repository: @repository
+= render 'shared/file_highlight', blob: viewer.blob
diff --git a/app/views/projects/settings/ci_cd/_badge.html.haml b/app/views/projects/settings/ci_cd/_badge.html.haml
index d14360913a4..82c8ec088e5 100644
--- a/app/views/projects/settings/ci_cd/_badge.html.haml
+++ b/app/views/projects/settings/ci_cd/_badge.html.haml
@@ -15,14 +15,14 @@
           .col-md-2.text-center
             Markdown
           .col-md-10.code.js-syntax-highlight
-            = highlight('.md', badge.to_markdown)
+            = highlight('.md', badge.to_markdown, language: 'markdown')
         .row
           %hr
         .row
           .col-md-2.text-center
             HTML
           .col-md-10.code.js-syntax-highlight
-            = highlight('.html', badge.to_html)
+            = highlight('.html', badge.to_html, language: 'html')
         .row
           %hr
         .row
diff --git a/app/views/search/results/_snippet_blob.html.haml b/app/views/search/results/_snippet_blob.html.haml
index 8b95bdf9747..b4ecd7bbae9 100644
--- a/app/views/search/results/_snippet_blob.html.haml
+++ b/app/views/search/results/_snippet_blob.html.haml
@@ -39,7 +39,7 @@
         .blob-content
           - snippet_chunks.each do |chunk|
             - unless chunk[:data].empty?
-              = highlight(snippet.file_name, chunk[:data], repository: nil, plain: snippet.blob.no_highlighting?)
+              = highlight(snippet.file_name, chunk[:data])
             - else
               .file-content.code
                 .nothing-here-block Empty file
diff --git a/app/views/shared/_file_highlight.html.haml b/app/views/shared/_file_highlight.html.haml
index 8d64cb5d698..5073e6ad48f 100644
--- a/app/views/shared/_file_highlight.html.haml
+++ b/app/views/shared/_file_highlight.html.haml
@@ -1,5 +1,3 @@
-- repository = nil unless local_assigns.key?(:repository)
-
 .file-content.code.js-syntax-highlight
   .line-numbers
     - if blob.data.present?
@@ -13,4 +11,6 @@
           = link_icon
           = i
   .blob-content{ data: { blob_id: blob.id } }
-    = highlight(blob.path, blob.data, repository: repository, plain: blob.no_highlighting?)
+    %pre.code.highlight
+      %code
+        = blob.present.highlight
diff --git a/app/views/sherlock/queries/_general.html.haml b/app/views/sherlock/queries/_general.html.haml
index ddc089b0bd7..52c7bc47ca7 100644
--- a/app/views/sherlock/queries/_general.html.haml
+++ b/app/views/sherlock/queries/_general.html.haml
@@ -36,7 +36,7 @@
       %li
         .code.js-syntax-highlight.sherlock-code
           :preserve
-            #{highlight("#{@query.id}.sql", @query.formatted_query)}
+            #{highlight("#{@query.id}.sql", @query.formatted_query, language: 'sql')}
 
   .card
     .card-header
diff --git a/app/views/sherlock/transactions/_queries.html.haml b/app/views/sherlock/transactions/_queries.html.haml
index c1ec4b91bb6..5e224f3aa0e 100644
--- a/app/views/sherlock/transactions/_queries.html.haml
+++ b/app/views/sherlock/transactions/_queries.html.haml
@@ -17,7 +17,7 @@
               = t('sherlock.milliseconds')
             %td
               .code.js-syntax-highlight.sherlock-code
-                = highlight("#{query.id}.sql", query.formatted_query)
+                = highlight("#{query.id}.sql", query.formatted_query, language: 'sql')
             %td
               = link_to(t('sherlock.view'),
                 sherlock_transaction_query_path(@transaction, query),
diff --git a/lib/gitlab/blame.rb b/lib/gitlab/blame.rb
index 0d79594363e..f1a653a9d95 100644
--- a/lib/gitlab/blame.rb
+++ b/lib/gitlab/blame.rb
@@ -43,8 +43,7 @@ module Gitlab
 
     def highlighted_lines
       @blob.load_all_data!
-      @highlighted_lines ||=
-        Gitlab::Highlight.highlight(@blob.path, @blob.data, repository: repository).lines
+      @highlighted_lines ||= @blob.present.highlight.lines
     end
 
     def project
diff --git a/lib/gitlab/conflict/file.rb b/lib/gitlab/conflict/file.rb
index 30911b49b18..501c2111530 100644
--- a/lib/gitlab/conflict/file.rb
+++ b/lib/gitlab/conflict/file.rb
@@ -3,6 +3,7 @@ module Gitlab
     class File
       include Gitlab::Routing
       include IconsHelper
+      include Gitlab::Utils::StrongMemoize
 
       CONTEXT_LINES = 3
 
@@ -30,11 +31,8 @@ module Gitlab
       end
 
       def highlight_lines!
-        their_file = lines.reject { |line| line.type == 'new' }.map(&:text).join("\n")
-        our_file = lines.reject { |line| line.type == 'old' }.map(&:text).join("\n")
-
-        their_highlight = Gitlab::Highlight.highlight(their_path, their_file, repository: repository).lines
-        our_highlight = Gitlab::Highlight.highlight(our_path, our_file, repository: repository).lines
+        their_highlight = Gitlab::Highlight.highlight(their_path, their_lines, language: their_language).lines
+        our_highlight = Gitlab::Highlight.highlight(our_path, our_lines, language: our_language).lines
 
         lines.each do |line|
           line.rich_text =
@@ -182,6 +180,34 @@ module Gitlab
             raw_line[:line_new], parent_file: self)
         end
       end
+
+      def their_language
+        strong_memoize(:their_language) do
+          repository.gitattribute(their_path, 'gitlab-language')
+        end
+      end
+
+      def our_language
+        strong_memoize(:our_language) do
+          if our_path == their_path
+            their_language
+          else
+            repository.gitattribute(our_path, 'gitlab-language')
+          end
+        end
+      end
+
+      def their_lines
+        strong_memoize(:their_lines) do
+          lines.reject { |line| line.type == 'new' }.map(&:text).join("\n")
+        end
+      end
+
+      def our_lines
+        strong_memoize(:our_lines) do
+          lines.reject { |line| line.type == 'old' }.map(&:text).join("\n")
+        end
+      end
     end
   end
 end
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index a605ddb5c33..1d833183ec3 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -79,7 +79,7 @@ module Gitlab
         return [] unless blob
 
         blob.load_all_data!
-        Gitlab::Highlight.highlight(blob.path, blob.data, repository: repository).lines
+        blob.present.highlight.lines
       end
     end
   end
diff --git a/lib/gitlab/highlight.rb b/lib/gitlab/highlight.rb
index 83095acc528..a4e60bbd828 100644
--- a/lib/gitlab/highlight.rb
+++ b/lib/gitlab/highlight.rb
@@ -4,22 +4,25 @@ module Gitlab
   class Highlight
     TIMEOUT_BACKGROUND = 30.seconds
     TIMEOUT_FOREGROUND = 3.seconds
+    MAXIMUM_TEXT_HIGHLIGHT_SIZE = 1.megabyte
 
-    def self.highlight(blob_name, blob_content, repository: nil, plain: false)
-      new(blob_name, blob_content, repository: repository)
+    def self.highlight(blob_name, blob_content, language: nil, plain: false)
+      new(blob_name, blob_content, language: language)
         .highlight(blob_content, continue: false, plain: plain)
     end
 
     attr_reader :blob_name
 
-    def initialize(blob_name, blob_content, repository: nil)
+    def initialize(blob_name, blob_content, language: nil)
       @formatter = Rouge::Formatters::HTMLGitlab
-      @repository = repository
+      @language = language
       @blob_name = blob_name
       @blob_content = blob_content
     end
 
     def highlight(text, continue: true, plain: false)
+      plain ||= text.length > MAXIMUM_TEXT_HIGHLIGHT_SIZE
+
       highlighted_text = highlight_text(text, continue: continue, plain: plain)
       highlighted_text = link_dependencies(text, highlighted_text) if blob_name
       highlighted_text
@@ -36,11 +39,9 @@ module Gitlab
     private
 
     def custom_language
-      language_name = @repository && @repository.gitattribute(@blob_name, 'gitlab-language')
-
-      return nil unless language_name
+      return nil unless @language
 
-      Rouge::Lexer.find_fancy(language_name)
+      Rouge::Lexer.find_fancy(@language)
     end
 
     def highlight_text(text, continue: true, plain: false)
diff --git a/lib/gitlab/project_search_results.rb b/lib/gitlab/project_search_results.rb
index 3a202d915e3..04df881bf03 100644
--- a/lib/gitlab/project_search_results.rb
+++ b/lib/gitlab/project_search_results.rb
@@ -82,7 +82,7 @@ module Gitlab
         ref: ref,
         startline: startline,
         data: data.join,
-        project_id: project ? project.id : nil
+        project: project
       )
     end
 
diff --git a/lib/gitlab/search_results.rb b/lib/gitlab/search_results.rb
index 5ce3eda2ccb..458737f31eb 100644
--- a/lib/gitlab/search_results.rb
+++ b/lib/gitlab/search_results.rb
@@ -4,8 +4,10 @@ module Gitlab
   class SearchResults
     class FoundBlob
       include EncodingHelper
+      include Presentable
+      include BlobLanguageFromGitAttributes
 
-      attr_reader :id, :filename, :basename, :ref, :startline, :data, :project_id
+      attr_reader :id, :filename, :basename, :ref, :startline, :data, :project
 
       def initialize(opts = {})
         @id = opts.fetch(:id, nil)
@@ -15,6 +17,11 @@ module Gitlab
         @startline = opts.fetch(:startline, nil)
         @data = encode_utf8(opts.fetch(:data, nil))
         @per_page = opts.fetch(:per_page, 20)
+        @project = opts.fetch(:project, nil)
+        # Some caller does not have project object (e.g. elastic search),
+        # yet they can trigger many calls in one go,
+        # causing duplicated queries.
+        # Allow those to just pass project_id instead.
         @project_id = opts.fetch(:project_id, nil)
       end
 
@@ -22,8 +29,12 @@ module Gitlab
         filename
       end
 
-      def no_highlighting?
-        false
+      def project_id
+        @project_id || @project&.id
+      end
+
+      def present
+        super(presenter_class: BlobPresenter)
       end
     end
 
diff --git a/spec/features/search/user_searches_for_wiki_pages_spec.rb b/spec/features/search/user_searches_for_wiki_pages_spec.rb
index 3ee753b7d23..7225ca65492 100644
--- a/spec/features/search/user_searches_for_wiki_pages_spec.rb
+++ b/spec/features/search/user_searches_for_wiki_pages_spec.rb
@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe 'User searches for wiki pages', :js do
   let(:user) { create(:user) }
-  let(:project) { create(:project, :wiki_repo, namespace: user.namespace) }
+  let(:project) { create(:project, :repository, :wiki_repo, namespace: user.namespace) }
   let!(:wiki_page) { create(:wiki_page, wiki: project.wiki, attrs: { title: 'test_wiki', content: 'Some Wiki content' }) }
 
   before do
diff --git a/spec/helpers/blob_helper_spec.rb b/spec/helpers/blob_helper_spec.rb
index 1c216b3fe97..f709f152c92 100644
--- a/spec/helpers/blob_helper_spec.rb
+++ b/spec/helpers/blob_helper_spec.rb
@@ -3,63 +3,13 @@ require 'spec_helper'
 describe BlobHelper do
   include TreeHelper
 
-  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") }
-  let(:multiline_content) do
-    %q(
-    def test(input):
-      """This is line 1 of a multi-line comment.
-      This is line 2.
-      """
-    )
-  end
-
   describe '#highlight' do
-    it 'returns plaintext for unknown lexer context' do
-      result = helper.highlight(blob_name, no_context_content)
-      expect(result).to eq(%[<pre class="code highlight"><code><span id="LC1" class="line" lang="">:type "assem"))</span></code></pre>])
+    it 'wraps highlighted content' do
+      expect(helper.highlight('test.rb', '52')).to eq(%q[<pre class="code highlight"><code><span id="LC1" class="line" lang="ruby"><span class="mi">52</span></span></code></pre>])
     end
 
-    it 'returns plaintext for long blobs' do
-      stub_const('Blob::MAXIMUM_TEXT_HIGHLIGHT_SIZE', 1)
-      result = helper.highlight(blob_name, blob_content)
-
-      expect(result).to eq(%[<pre class="code highlight"><code><span id="LC1" class="line" lang="">(make-pathname :defaults name</span>\n<span id="LC2" class="line" lang="">:type "assem"))</span></code></pre>])
-    end
-
-    it 'highlights single block' do
-      expected = %Q[<pre class="code highlight"><code><span id="LC1" class="line" lang="common_lisp"><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" lang="common_lisp"><span class="ss">:type</span> <span class="s">"assem"</span><span class="p">))</span></span></code></pre>]
-
-      expect(helper.highlight(blob_name, blob_content)).to eq(expected)
-    end
-
-    it 'highlights multi-line comments' do
-      result = helper.highlight(blob_name, multiline_content)
-      html = Nokogiri::HTML(result)
-      lines = html.search('.s')
-      expect(lines.count).to eq(3)
-      expect(lines[0].text).to eq('"""This is line 1 of a multi-line comment.')
-      expect(lines[1].text).to eq('      This is line 2.')
-      expect(lines[2].text).to eq('      """')
-    end
-
-    context 'diff highlighting' do
-      let(:blob_name) { 'test.diff' }
-      let(:blob_content) { "+aaa\n+bbb\n- ccc\n ddd\n"}
-      let(:expected) do
-        %q(<pre class="code highlight"><code><span id="LC1" class="line" lang="diff"><span class="gi">+aaa</span></span>
-<span id="LC2" class="line" lang="diff"><span class="gi">+bbb</span></span>
-<span id="LC3" class="line" lang="diff"><span class="gd">- ccc</span></span>
-<span id="LC4" class="line" lang="diff"> ddd</span></code></pre>)
-      end
-
-      it 'highlights each line properly' do
-        result = helper.highlight(blob_name, blob_content)
-        expect(result).to eq(expected)
-      end
+    it 'handles plain version' do
+      expect(helper.highlight('test.rb', '52', plain: true)).to eq(%q[<pre class="code highlight"><code><span id="LC1" class="line" lang="">52</span></code></pre>])
     end
   end
 
diff --git a/spec/lib/gitlab/git/attributes_parser_spec.rb b/spec/lib/gitlab/git/attributes_parser_spec.rb
index 18ebfef38f0..f431d4e2a53 100644
--- a/spec/lib/gitlab/git/attributes_parser_spec.rb
+++ b/spec/lib/gitlab/git/attributes_parser_spec.rb
@@ -94,7 +94,7 @@ describe Gitlab::Git::AttributesParser, :seed_helper do
     # It's a bit hard to test for something _not_ being processed. As such we'll
     # just test the number of entries.
     it 'ignores any comments and empty lines' do
-      expect(subject.patterns.length).to eq(10)
+      expect(subject.patterns.length).to eq(12)
     end
   end
 
@@ -126,7 +126,7 @@ describe Gitlab::Git::AttributesParser, :seed_helper do
 
   describe '#each_line' do
     it 'iterates over every line in the attributes file' do
-      args = [String] * 14 # the number of lines in the file
+      args = [String] * 16 # the number of lines in the file
 
       expect { |b| subject.each_line(&b) }.to yield_successive_args(*args)
     end
diff --git a/spec/lib/gitlab/git/repository_spec.rb b/spec/lib/gitlab/git/repository_spec.rb
index 51eb997a325..9a443fa7f20 100644
--- a/spec/lib/gitlab/git/repository_spec.rb
+++ b/spec/lib/gitlab/git/repository_spec.rb
@@ -1194,6 +1194,34 @@ describe Gitlab::Git::Repository, :seed_helper do
     end
   end
 
+  describe '#gitattribute' do
+    let(:repository) { Gitlab::Git::Repository.new('default', TEST_GITATTRIBUTES_REPO_PATH, '') }
+
+    after do
+      ensure_seeds
+    end
+
+    it 'returns matching language attribute' do
+      expect(repository.gitattribute("custom-highlighting/test.gitlab-custom", 'gitlab-language')).to eq('ruby')
+    end
+
+    it 'returns matching language attribute with additional options' do
+      expect(repository.gitattribute("custom-highlighting/test.gitlab-cgi", 'gitlab-language')).to eq('erb?parent=json')
+    end
+
+    it 'returns nil if nothing matches' do
+      expect(repository.gitattribute("report.xslt", 'gitlab-language')).to eq(nil)
+    end
+
+    context 'without gitattributes file' do
+      let(:repository) { Gitlab::Git::Repository.new('default', TEST_REPO_PATH, '') }
+
+      it 'returns nil' do
+        expect(repository.gitattribute("README.md", 'gitlab-language')).to eq(nil)
+      end
+    end
+  end
+
   describe '#ref_exists?' do
     it 'returns true for an existing tag' do
       expect(repository.ref_exists?('refs/heads/master')).to eq(true)
diff --git a/spec/lib/gitlab/highlight_spec.rb b/spec/lib/gitlab/highlight_spec.rb
index 88f7099ff3c..fe0e9702f8a 100644
--- a/spec/lib/gitlab/highlight_spec.rb
+++ b/spec/lib/gitlab/highlight_spec.rb
@@ -5,44 +5,85 @@ describe Gitlab::Highlight do
 
   let(:project) { create(:project, :repository) }
   let(:repository) { project.repository }
-  let(:commit) { project.commit(sample_commit.id) }
-
-  describe 'custom highlighting from .gitattributes' do
-    let(:branch) { 'gitattributes' }
-    let(:blob) { repository.blob_at_branch(branch, path) }
 
+  describe 'language provided' do
     let(:highlighter) do
-      described_class.new(blob.path, blob.data, repository: repository)
+      described_class.new('foo.erb', 'bar', language: 'erb?parent=json')
     end
 
-    before do
-      project.change_head('gitattributes')
+    it 'sets correct lexer' do
+      expect(highlighter.lexer.tag).to eq 'erb'
+      expect(highlighter.lexer.parent.tag).to eq 'json'
     end
+  end
 
-    describe 'basic language selection' do
-      let(:path) { 'custom-highlighting/test.gitlab-custom' }
-      it 'highlights as ruby' do
-        expect(highlighter.lexer.tag).to eq 'ruby'
-      end
+  describe '#highlight' do
+    let(:file_name) { 'test.lisp' }
+    let(:no_context_content) { ":type \"assem\"))" }
+    let(:content) { "(make-pathname :defaults name\n#{no_context_content}" }
+    let(:multiline_content) do
+      %q(
+      def test(input):
+        """This is line 1 of a multi-line comment.
+        This is line 2.
+        """
+      )
+    end
+
+    it 'highlights' do
+      expected = %Q[<span id="LC1" class="line" lang="common_lisp"><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" lang="common_lisp"><span class="ss">:type</span> <span class="s">"assem"</span><span class="p">))</span></span>]
+
+      expect(described_class.highlight(file_name, content)).to eq(expected)
+    end
+
+    it 'returns plain version for unknown lexer context' do
+      result = described_class.highlight(file_name, no_context_content)
+
+      expect(result).to eq(%[<span id="LC1" class="line" lang="">:type "assem"))</span>])
     end
 
-    describe 'cgi options' do
-      let(:path) { 'custom-highlighting/test.gitlab-cgi' }
+    it 'returns plain version for long content' do
+      stub_const('Gitlab::Highlight::MAXIMUM_TEXT_HIGHLIGHT_SIZE', 1)
+      result = described_class.highlight(file_name, content)
 
-      it 'highlights as json with erb' do
-        expect(highlighter.lexer.tag).to eq 'erb'
-        expect(highlighter.lexer.parent.tag).to eq 'json'
+      expect(result).to eq(%[<span id="LC1" class="line" lang="">(make-pathname :defaults name</span>\n<span id="LC2" class="line" lang="">:type "assem"))</span>])
+    end
+
+    it 'highlights multi-line comments' do
+      result = described_class.highlight(file_name, multiline_content)
+      html = Nokogiri::HTML(result)
+      lines = html.search('.s')
+
+      expect(lines.count).to eq(3)
+      expect(lines[0].text).to eq('"""This is line 1 of a multi-line comment.')
+      expect(lines[1].text).to eq('        This is line 2.')
+      expect(lines[2].text).to eq('        """')
+    end
+
+    context 'diff highlighting' do
+      let(:file_name) { 'test.diff' }
+      let(:content) { "+aaa\n+bbb\n- ccc\n ddd\n"}
+      let(:expected) do
+        %q(<span id="LC1" class="line" lang="diff"><span class="gi">+aaa</span></span>
+<span id="LC2" class="line" lang="diff"><span class="gi">+bbb</span></span>
+<span id="LC3" class="line" lang="diff"><span class="gd">- ccc</span></span>
+<span id="LC4" class="line" lang="diff"> ddd</span>)
+      end
+
+      it 'highlights each line properly' do
+        result = described_class.highlight(file_name, content)
+
+        expect(result).to eq(expected)
       end
     end
-  end
 
-  describe '#highlight' do
     describe 'with CRLF' do
       let(:branch) { 'crlf-diff' }
       let(:path) { 'files/whitespace' }
       let(:blob) { repository.blob_at_branch(branch, path) }
       let(:lines) do
-        described_class.highlight(blob.path, blob.data, repository: repository).lines
+        described_class.highlight(blob.path, blob.data).lines
       end
 
       it 'strips extra LFs' do
diff --git a/spec/models/concerns/blob_language_from_git_attributes_spec.rb b/spec/models/concerns/blob_language_from_git_attributes_spec.rb
new file mode 100644
index 00000000000..7f05073b08e
--- /dev/null
+++ b/spec/models/concerns/blob_language_from_git_attributes_spec.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe BlobLanguageFromGitAttributes do
+  include FakeBlobHelpers
+
+  let(:project) { build(:project, :repository) }
+
+  describe '#language_from_gitattributes' do
+    subject(:blob) { fake_blob(path: 'file.md') }
+
+    it 'returns return value from gitattribute' do
+      expect(blob.project.repository).to receive(:gitattribute).with(blob.path, 'gitlab-language').and_return('erb?parent=json')
+
+      expect(blob.language_from_gitattributes).to eq('erb?parent=json')
+    end
+
+    it 'returns nil if project is absent' do
+      allow(blob).to receive(:project).and_return(nil)
+
+      expect(blob.language_from_gitattributes).to eq(nil)
+    end
+  end
+end
diff --git a/spec/presenters/blob_presenter_spec.rb b/spec/presenters/blob_presenter_spec.rb
new file mode 100644
index 00000000000..e85e7a41017
--- /dev/null
+++ b/spec/presenters/blob_presenter_spec.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe BlobPresenter, :seed_helper do
+  let(:repository) { Gitlab::Git::Repository.new('default', TEST_REPO_PATH, '') }
+
+  let(:git_blob) do
+    Gitlab::Git::Blob.find(
+      repository,
+      'fa1b1e6c004a68b7d8763b86455da9e6b23e36d6',
+      'files/ruby/regex.rb'
+    )
+  end
+  let(:blob) { Blob.new(git_blob) }
+
+  describe '#highlight' do
+    subject { described_class.new(blob) }
+
+    it 'returns highlighted content' do
+      expect(Gitlab::Highlight).to receive(:highlight).with('files/ruby/regex.rb', git_blob.data, plain: nil, language: nil)
+
+      subject.highlight
+    end
+
+    it 'returns plain content when :plain is true' do
+      expect(Gitlab::Highlight).to receive(:highlight).with('files/ruby/regex.rb', git_blob.data, plain: true, language: nil)
+
+      subject.highlight(plain: true)
+    end
+
+    context 'gitlab-language contains a match' do
+      before do
+        allow(blob).to receive(:language_from_gitattributes).and_return('ruby')
+      end
+
+      it 'passes language to inner call' do
+        expect(Gitlab::Highlight).to receive(:highlight).with('files/ruby/regex.rb', git_blob.data, plain: nil, language: 'ruby')
+
+        subject.highlight
+      end
+    end
+  end
+end
diff --git a/spec/support/helpers/seed_helper.rb b/spec/support/helpers/seed_helper.rb
index 25781f5e679..90d7f60fdeb 100644
--- a/spec/support/helpers/seed_helper.rb
+++ b/spec/support/helpers/seed_helper.rb
@@ -1,15 +1,18 @@
+# frozen_string_literal: true
+
 require_relative 'test_env'
 
 # This file is specific to specs in spec/lib/gitlab/git/
 
 SEED_STORAGE_PATH      = TestEnv.repos_path
-TEST_REPO_PATH         = 'gitlab-git-test.git'.freeze
-TEST_NORMAL_REPO_PATH  = 'not-bare-repo.git'.freeze
-TEST_MUTABLE_REPO_PATH = 'mutable-repo.git'.freeze
-TEST_BROKEN_REPO_PATH  = 'broken-repo.git'.freeze
+TEST_REPO_PATH         = 'gitlab-git-test.git'
+TEST_NORMAL_REPO_PATH  = 'not-bare-repo.git'
+TEST_MUTABLE_REPO_PATH = 'mutable-repo.git'
+TEST_BROKEN_REPO_PATH  = 'broken-repo.git'
+TEST_GITATTRIBUTES_REPO_PATH = 'with-git-attributes.git'
 
 module SeedHelper
-  GITLAB_GIT_TEST_REPO_URL = File.expand_path('../gitlab-git-test.git', __dir__).freeze
+  GITLAB_GIT_TEST_REPO_URL = File.expand_path('../gitlab-git-test.git', __dir__)
 
   def ensure_seeds
     if File.exist?(SEED_STORAGE_PATH)
@@ -66,6 +69,11 @@ module SeedHelper
   end
 
   def create_git_attributes
+    system(git_env, *%W(#{Gitlab.config.git.bin_path} clone --bare #{TEST_REPO_PATH} #{TEST_GITATTRIBUTES_REPO_PATH}),
+           chdir: SEED_STORAGE_PATH,
+           out: '/dev/null',
+           err: '/dev/null')
+
     dir = File.join(SEED_STORAGE_PATH, 'with-git-attributes.git', 'info')
 
     FileUtils.mkdir_p(dir)
@@ -82,6 +90,8 @@ foo/bar.* foo
 *.cgi     key=value?p1=v1&p2=v2
 /*.png    gitlab-language=png
 *.binary  binary
+/custom-highlighting/*.gitlab-custom gitlab-language=ruby
+/custom-highlighting/*.gitlab-cgi gitlab-language=erb?parent=json
 
 # This uses a tab instead of spaces to ensure the parser also supports this.
 *.md\tgitlab-language=markdown
diff --git a/spec/views/projects/blob/_viewer.html.haml_spec.rb b/spec/views/projects/blob/_viewer.html.haml_spec.rb
index aedbaa66d34..95f7f87d37b 100644
--- a/spec/views/projects/blob/_viewer.html.haml_spec.rb
+++ b/spec/views/projects/blob/_viewer.html.haml_spec.rb
@@ -29,6 +29,8 @@ describe 'projects/blob/_viewer.html.haml' do
     controller.params[:namespace_id] = project.namespace.to_param
     controller.params[:project_id] = project.to_param
     controller.params[:id] = File.join('master', blob.path)
+
+    allow(project.repository).to receive(:gitattribute).and_return(nil)
   end
 
   def render_view