Subclass TaskList::Filter to fix a bug

Instead of using a fork, we subclass the filter and only apply the
`task-list` class to list items that actually are task lists.

Closes #1645

See https://github.com/github/task_list/pull/60

Gemfile

@@ -95,7 +95,7 @@ gem "seed-fu"
 # Markdown and HTML processing
 gem 'html-pipeline', '~> 1.11.0'
-gem 'task_list',     '~> 1.0.0', require: 'task_list/railtie'
+gem 'task_list',     '1.0.2', require: 'task_list/railtie'
 gem 'github-markup'
 gem 'redcarpet',     '~> 3.2.3'
 gem 'RedCloth'

Gemfile.lock

@@ -339,7 +339,7 @@ GEM
     method_source (0.8.2)
     mime-types (1.25.1)
     mimemagic (0.3.0)
-    mini_portile (0.6.1)
+    mini_portile (0.6.2)
     minitest (5.3.5)
     mousetrap-rails (1.4.6)
     multi_json (1.10.1)
@@ -351,7 +351,7 @@ GEM
       net-ssh (>= 2.6.5)
     net-ssh (2.8.0)
     newrelic_rpm (3.9.4.245)
-    nokogiri (1.6.5)
+    nokogiri (1.6.6.2)
       mini_portile (~> 0.6.0)
     nprogress-rails (0.1.2.3)
     oauth (0.4.7)
@@ -805,7 +805,7 @@ DEPENDENCIES
   spring-commands-spinach (= 1.0.0)
   stamp
   state_machine
-  task_list (~> 1.0.0)
+  task_list (= 1.0.2)
   test_after_commit
   thin
   tinder (~> 1.9.2)

app/assets/stylesheets/pages/notes.scss

@@ -79,11 +79,11 @@ ul.notes {
         word-wrap: break-word;
         @include md-typography;
-        // Reduce left padding of first ul element
+        // Reduce left padding of first task list ul element
         ul.task-list:first-child {
           padding-left: 10px;
-          // sub-lists should be padded normally
+          // sub-tasks should be padded normally
           ul {
             padding-left: 20px;
           }

lib/gitlab/markdown.rb

 require 'html/pipeline'
-require 'task_list/filter'
 module Gitlab
   # Custom parser for GitLab-flavored Markdown
@@ -19,6 +18,7 @@ module Markdown
     autoload :SanitizationFilter,           'gitlab/markdown/sanitization_filter'
     autoload :SnippetReferenceFilter,       'gitlab/markdown/snippet_reference_filter'
     autoload :TableOfContentsFilter,        'gitlab/markdown/table_of_contents_filter'
+    autoload :TaskListFilter,               'gitlab/markdown/task_list_filter'
     autoload :UserReferenceFilter,          'gitlab/markdown/user_reference_filter'
     # Public: Parse the provided text with GitLab-Flavored Markdown
@@ -113,7 +113,7 @@ def filters
         Gitlab::Markdown::CommitReferenceFilter,
         Gitlab::Markdown::LabelReferenceFilter,
-        TaskList::Filter
+        Gitlab::Markdown::TaskListFilter
       ]
     end
   end

lib/gitlab/markdown/task_list_filter.rb

+require 'task_list/filter'
+
+module Gitlab
+  module Markdown
+    # Work around a bug in the default TaskList::Filter that adds a `task-list`
+    # class to every list element, regardless of whether or not it contains a
+    # task list.
+    #
+    # This is a (hopefully) temporary fix, pending a new release of the
+    # task_list gem.
+    #
+    # See https://github.com/github/task_list/pull/60
+    class TaskListFilter < TaskList::Filter
+      def add_css_class(node, *new_class_names)
+        if new_class_names.include?('task-list')
+          super if node.children.any? { |c| c['class'] == 'task-list-item' }
+        else
+          super
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/markdown/task_list_filter_spec.rb

+require 'spec_helper'
+
+module Gitlab::Markdown
+  describe TaskListFilter do
+    def filter(html, options = {})
+      described_class.call(html, options)
+    end
+
+    it 'does not apply `task-list` class to non-task lists' do
+      exp = act = %(<ul><li>Item</li></ul>)
+      expect(filter(act).to_html).to eq exp
+    end
+  end
+end