Merge pull request #7964 from mr-vinn/task-lists

Add task lists to issues and merge requests

30 files changed, 501 insertions, 9 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 857a5bc9234..14bb88f22a5 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -18,6 +18,7 @@ v 7.4.0
   - Add Pushover service integration (Sullivan Senechal)
   - Add select field type for services options (Sullivan Senechal)
   - Add cross-project references to the Markdown parser (Vinnie Okada)
+  - Add task lists to issue and merge request descriptions (Vinnie Okada)
 
 v 7.3.2
   - Fix creating new file via web editor
diff --git a/app/assets/javascripts/issue.js.coffee b/app/assets/javascripts/issue.js.coffee
index 36935a0a159..f2b531fb2b1 100644
--- a/app/assets/javascripts/issue.js.coffee
+++ b/app/assets/javascripts/issue.js.coffee
@@ -6,4 +6,28 @@ class Issue
     $(".issue-box .inline-update").on "change", "#issue_assignee_id", ->
       $(this).submit()
 
+    if $("a.btn-close").length
+      $("li.task-list-item input:checkbox").prop("disabled", false)
+
+    $(".task-list-item input:checkbox").on "click", ->
+      is_checked = $(this).prop("checked")
+      if $(this).is(":checked")
+        state_event = "task_check"
+      else
+        state_event = "task_uncheck"
+
+      mr_url = $("form.edit-issue").first().attr("action")
+      mr_num = mr_url.match(/\d+$/)
+      task_num = 0
+      $("li.task-list-item input:checkbox").each( (index, e) =>
+        if e == this
+          task_num = index + 1
+      )
+
+      $.ajax
+        type: "PATCH"
+        url: mr_url
+        data: "issue[state_event]=" + state_event +
+          "&issue[task_num]=" + task_num
+
 @Issue = Issue
diff --git a/app/assets/javascripts/merge_request.js.coffee b/app/assets/javascripts/merge_request.js.coffee
index 4c9f20ae6fa..203c721c30c 100644
--- a/app/assets/javascripts/merge_request.js.coffee
+++ b/app/assets/javascripts/merge_request.js.coffee
@@ -17,6 +17,8 @@ class MergeRequest
 
     disableButtonIfEmptyField '#commit_message', '.accept_merge_request'
 
+    if $("a.close-mr-link").length
+      $("li.task-list-item input:checkbox").prop("disabled", false)
 
   # Local jQuery finder
   $: (selector) ->
@@ -72,6 +74,27 @@ class MergeRequest
       this.$('.remove_source_branch_in_progress').hide()
       this.$('.remove_source_branch_widget.failed').show()
 
+    this.$(".task-list-item input:checkbox").on "click", ->
+      is_checked = $(this).prop("checked")
+      if $(this).is(":checked")
+        state_event = "task_check"
+      else
+        state_event = "task_uncheck"
+
+      mr_url = $("form.edit-merge_request").first().attr("action")
+      mr_num = mr_url.match(/\d+$/)
+      task_num = 0
+      $("li.task-list-item input:checkbox").each( (index, e) =>
+        if e == this
+          task_num = index + 1
+      )
+
+      $.ajax
+        type: "PATCH"
+        url: mr_url
+        data: "merge_request[state_event]=" + state_event +
+          "&merge_request[task_num]=" + task_num
+
   activateTab: (action) ->
     this.$('.merge-request-tabs li').removeClass 'active'
     this.$('.tab-content').hide()
diff --git a/app/assets/stylesheets/generic/common.scss b/app/assets/stylesheets/generic/common.scss
index 803219a2e86..cd2f4e45e3c 100644
--- a/app/assets/stylesheets/generic/common.scss
+++ b/app/assets/stylesheets/generic/common.scss
@@ -356,3 +356,6 @@ table {
   font-size: 42px;
 }
 
+.task-status {
+  margin-left: 10px;
+}
diff --git a/app/assets/stylesheets/generic/lists.scss b/app/assets/stylesheets/generic/lists.scss
index d347ab2c2e4..2653bfbf831 100644
--- a/app/assets/stylesheets/generic/lists.scss
+++ b/app/assets/stylesheets/generic/lists.scss
@@ -122,3 +122,7 @@ ul.bordered-list {
     }
   }
 }
+
+li.task-list-item {
+  list-style-type: none;
+}
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index 9e7a55b23fd..c6d526f05c5 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -152,7 +152,7 @@ class Projects::IssuesController < Projects::ApplicationController
   def issue_params
     params.require(:issue).permit(
       :title, :assignee_id, :position, :description,
-      :milestone_id, :state_event, label_ids: []
+      :milestone_id, :state_event, :task_num, label_ids: []
     )
   end
 end
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index e13773d6465..20a733b10e1 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -250,7 +250,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     params.require(:merge_request).permit(
       :title, :assignee_id, :source_project_id, :source_branch,
       :target_project_id, :target_branch, :milestone_id,
-      :state_event, :description, label_ids: []
+      :state_event, :description, :task_num, label_ids: []
     )
   end
 end
diff --git a/app/models/concerns/taskable.rb b/app/models/concerns/taskable.rb
new file mode 100644
index 00000000000..410e8dc820b
--- /dev/null
+++ b/app/models/concerns/taskable.rb
@@ -0,0 +1,51 @@
+# Contains functionality for objects that can have task lists in their
+# descriptions.  Task list items can be added with Markdown like "* [x] Fix
+# bugs".
+#
+# Used by MergeRequest and Issue
+module Taskable
+  TASK_PATTERN_MD = /^(?<bullet> *[*-] *)\[(?<checked>[ xX])\]/.freeze
+  TASK_PATTERN_HTML = /^<li>\[(?<checked>[ xX])\]/.freeze
+
+  # Change the state of a task list item for this Taskable.  Edit the object's
+  # description by finding the nth task item and changing its checkbox
+  # placeholder to "[x]" if +checked+ is true, or "[ ]" if it's false.
+  # Note: task numbering starts with 1
+  def update_nth_task(n, checked)
+    index = 0
+    check_char = checked ? 'x' : ' '
+
+    # Do this instead of using #gsub! so that ActiveRecord detects that a field
+    # has changed.
+    self.description = self.description.gsub(TASK_PATTERN_MD) do |match|
+      index += 1
+      case index
+      when n then "#{$LAST_MATCH_INFO[:bullet]}[#{check_char}]"
+      else match
+      end
+    end
+
+    save
+  end
+
+  # Return true if this object's description has any task list items.
+  def tasks?
+    description && description.match(TASK_PATTERN_MD)
+  end
+
+  # Return a string that describes the current state of this Taskable's task
+  # list items, e.g. "20 tasks (12 done, 8 unfinished)"
+  def task_status
+    return nil unless description
+
+    num_tasks = 0
+    num_done = 0
+
+    description.scan(TASK_PATTERN_MD) do
+      num_tasks += 1
+      num_done += 1 unless $LAST_MATCH_INFO[:checked] == ' '
+    end
+
+    "#{num_tasks} tasks (#{num_done} done, #{num_tasks - num_done} unfinished)"
+  end
+end
diff --git a/app/models/issue.rb b/app/models/issue.rb
index 13152fdf94e..8a9e969248c 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -23,6 +23,7 @@ require 'file_size_validator'
 class Issue < ActiveRecord::Base
   include Issuable
   include InternalId
+  include Taskable
 
   ActsAsTaggableOn.strict_case_match = true
 
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index e0358c1889c..7c525b02f48 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -25,6 +25,7 @@ require Rails.root.join("lib/static_model")
 
 class MergeRequest < ActiveRecord::Base
   include Issuable
+  include Taskable
   include InternalId
 
   belongs_to :target_project, foreign_key: :target_project_id, class_name: "Project"
diff --git a/app/services/issues/update_service.rb b/app/services/issues/update_service.rb
index a0e57144435..5b2746ffecf 100644
--- a/app/services/issues/update_service.rb
+++ b/app/services/issues/update_service.rb
@@ -8,9 +8,14 @@ module Issues
         Issues::ReopenService.new(project, current_user, {}).execute(issue)
       when 'close'
         Issues::CloseService.new(project, current_user, {}).execute(issue)
+      when 'task_check'
+        issue.update_nth_task(params[:task_num].to_i, true)
+      when 'task_uncheck'
+        issue.update_nth_task(params[:task_num].to_i, false)
       end
 
-      if params.present? && issue.update_attributes(params.except(:state_event))
+      if params.present? && issue.update_attributes(params.except(:state_event,
+                                                                  :task_num))
         issue.reset_events_cache
 
         if issue.previous_changes.include?('milestone_id')
@@ -28,5 +33,12 @@ module Issues
 
       issue
     end
+
+    private
+
+    def update_task(issue, params, checked)
+      issue.update_nth_task(params[:task_num].to_i, checked)
+      params.except!(:task_num)
+    end
   end
 end
diff --git a/app/services/merge_requests/update_service.rb b/app/services/merge_requests/update_service.rb
index 6e416a0080c..fc26619cd17 100644
--- a/app/services/merge_requests/update_service.rb
+++ b/app/services/merge_requests/update_service.rb
@@ -17,9 +17,15 @@ module MergeRequests
         MergeRequests::ReopenService.new(project, current_user, {}).execute(merge_request)
       when 'close'
         MergeRequests::CloseService.new(project, current_user, {}).execute(merge_request)
+      when 'task_check'
+        merge_request.update_nth_task(params[:task_num].to_i, true)
+      when 'task_uncheck'
+        merge_request.update_nth_task(params[:task_num].to_i, false)
       end
 
-      if params.present? && merge_request.update_attributes(params.except(:state_event))
+      if params.present? && merge_request.update_attributes(
+        params.except(:state_event, :task_num)
+      )
         merge_request.reset_events_cache
 
         if merge_request.previous_changes.include?('milestone_id')
diff --git a/app/views/projects/issues/_issue.html.haml b/app/views/projects/issues/_issue.html.haml
index e089b5fa1cf..b125706781c 100644
--- a/app/views/projects/issues/_issue.html.haml
+++ b/app/views/projects/issues/_issue.html.haml
@@ -26,6 +26,10 @@
       %span
         %i.fa.fa-clock-o
         = issue.milestone.title
+    - if issue.tasks?
+      %span.task-status
+        = issue.task_status
+
     .pull-right
       %small updated #{time_ago_with_tooltip(issue.updated_at, 'bottom', 'issue_update_ago')}
 
diff --git a/app/views/projects/issues/show.html.haml b/app/views/projects/issues/show.html.haml
index 4c1ea098d98..e1849b3f8b8 100644
--- a/app/views/projects/issues/show.html.haml
+++ b/app/views/projects/issues/show.html.haml
@@ -48,7 +48,7 @@
     .description
       .wiki
         = preserve do
-          = markdown @issue.description
+          = markdown(@issue.description, parse_tasks: true)
   .context
     %cite.cgray
       = render partial: 'issue_context', locals: { issue: @issue }
diff --git a/app/views/projects/merge_requests/_merge_request.html.haml b/app/views/projects/merge_requests/_merge_request.html.haml
index 647e8873e9e..1ee2e1bdae8 100644
--- a/app/views/projects/merge_requests/_merge_request.html.haml
+++ b/app/views/projects/merge_requests/_merge_request.html.haml
@@ -27,7 +27,9 @@
       %span
         %i.fa.fa-clock-o
         = merge_request.milestone.title
-
+    - if merge_request.tasks?
+      %span.task-status
+        = merge_request.task_status
 
     .pull-right
       %small updated #{time_ago_with_tooltip(merge_request.updated_at, 'bottom', 'merge_request_updated_ago')}
diff --git a/app/views/projects/merge_requests/show/_mr_box.html.haml b/app/views/projects/merge_requests/show/_mr_box.html.haml
index f1aaba2010d..7e5a4eda508 100644
--- a/app/views/projects/merge_requests/show/_mr_box.html.haml
+++ b/app/views/projects/merge_requests/show/_mr_box.html.haml
@@ -18,7 +18,7 @@
     .description
       .wiki
         = preserve do
-          = markdown @merge_request.description
+          = markdown(@merge_request.description, parse_tasks: true)
 
   .context
     %cite.cgray
diff --git a/doc/markdown/markdown.md b/doc/markdown/markdown.md
index 5c095ed1487..6d96da76ad7 100644
--- a/doc/markdown/markdown.md
+++ b/doc/markdown/markdown.md
@@ -10,6 +10,7 @@
 * [Code and Syntax Highlighting](#code-and-syntax-highlighting)
 * [Emoji](#emoji)
 * [Special GitLab references](#special-gitlab-references)
+* [Task lists](#task-lists)
 
 **[Standard Markdown](#standard-markdown)**
 
@@ -183,6 +184,18 @@ GFM also recognizes references to commits, issues, and merge requests in other p
 - namespace/project!123 : for merge requests
 - namespace/project@1234567 : for commits
 
+## Task Lists
+
+You can add task lists to merge request and issue descriptions to keep track of to-do items.  To create a task, add an unordered list to the description in an issue or merge request, formatted like so:
+
+```no-highlight
+* [x] Completed task
+* [ ] Unfinished task
+    * [x] Nested task
+```
+
+Task lists can only be created in descriptions, not in titles or comments.  Task item state can be managed by editing the description's Markdown or by clicking the rendered checkboxes.
+
 # Standard Markdown
 
 ## Headers
diff --git a/features/project/issues/issues.feature b/features/project/issues/issues.feature
index ae6a03ce865..e989569ccd4 100644
--- a/features/project/issues/issues.feature
+++ b/features/project/issues/issues.feature
@@ -126,3 +126,36 @@ Feature: Project Issues
     When I click label 'bug'
     And I should see "Release 0.4" in issues
     And I should not see "Tweet control" in issues
+
+  Scenario: Issue description should render task checkboxes
+    Given project "Shop" has "Tasks-open" open issue with task markdown
+    When I visit issue page "Tasks-open"
+    Then I should see task checkboxes in the description
+
+  @javascript
+  Scenario: Issue notes should not render task checkboxes
+    Given project "Shop" has "Tasks-open" open issue with task markdown
+    When I visit issue page "Tasks-open"
+    And I leave a comment with task markdown
+    Then I should not see task checkboxes in the comment
+
+  # Task status in issues list
+
+  Scenario: Issues list should display task status
+    Given project "Shop" has "Tasks-open" open issue with task markdown
+    When I visit project "Shop" issues page
+    Then I should see the task status for issue "Tasks-open"
+
+  # Toggling task items
+
+  @javascript
+  Scenario: Task checkboxes should be enabled for an open issue
+    Given project "Shop" has "Tasks-open" open issue with task markdown
+    When I visit issue page "Tasks-open"
+    Then Task checkboxes should be enabled
+
+  @javascript
+  Scenario: Task checkboxes should be disabled for a closed issue
+    Given project "Shop" has "Tasks-closed" closed issue with task markdown
+    When I visit issue page "Tasks-closed"
+    Then Task checkboxes should be disabled
diff --git a/features/project/merge_requests.feature b/features/project/merge_requests.feature
index 60302c44ddb..e1e0edd0545 100644
--- a/features/project/merge_requests.feature
+++ b/features/project/merge_requests.feature
@@ -96,6 +96,16 @@ Feature: Project Merge Requests
     And I leave a comment with a header containing "Comment with a header"
     Then The comment with the header should not have an ID
 
+  Scenario: Merge request description should render task checkboxes
+    Given project "Shop" has "MR-task-open" open MR with task markdown
+    When I visit merge request page "MR-task-open"
+    Then I should see task checkboxes in the description
+
+  Scenario: Merge request notes should not render task checkboxes
+    Given project "Shop" has "MR-task-open" open MR with task markdown
+    When I visit merge request page "MR-task-open"
+    Then I should not see task checkboxes in the comment
+
   # Toggling inline comments
 
   @javascript
@@ -155,3 +165,26 @@ Feature: Project Merge Requests
     And I leave a comment like "Line is wrong" on line 39 of the second file
     And I click Side-by-side Diff tab
     Then I should see comments on the side-by-side diff page
+
+  # Task status in issues list
+
+  @now
+  Scenario: Merge requests list should display task status
+    Given project "Shop" has "MR-task-open" open MR with task markdown
+    When I visit project "Shop" merge requests page
+    Then I should see the task status for merge request "MR-task-open"
+
+  # Toggling task items
+
+  @javascript
+  Scenario: Task checkboxes should be enabled for an open merge request
+    Given project "Shop" has "MR-task-open" open MR with task markdown
+    When I visit merge request page "MR-task-open"
+    Then Task checkboxes should be enabled
+
+  @javascript
+  Scenario: Task checkboxes should be disabled for a closed merge request
+    Given project "Shop" has "MR-task-open" open MR with task markdown
+    And I visit merge request page "MR-task-open"
+    And I click link "Close"
+    Then Task checkboxes should be disabled
diff --git a/features/steps/project/issues/issues.rb b/features/steps/project/issues/issues.rb
index b55b3c6c8a2..26c3c7c14bc 100644
--- a/features/steps/project/issues/issues.rb
+++ b/features/steps/project/issues/issues.rb
@@ -153,6 +153,32 @@ class Spinach::Features::ProjectIssues < Spinach::FeatureSteps
            author: project.users.first)
   end
 
+  step 'project "Shop" has "Tasks-open" open issue with task markdown' do
+    desc_text = <<EOT.gsub(/^ {6}/, '')
+      * [ ] Task 1
+      * [x] Task 2
+EOT
+    create(:issue,
+           title: 'Tasks-open',
+           project: project,
+           author: project.users.first,
+           description: desc_text
+          )
+  end
+
+  step 'project "Shop" has "Tasks-closed" closed issue with task markdown' do
+    desc_text = <<EOT.gsub(/^ {6}/, '')
+      * [ ] Task 1
+      * [x] Task 2
+EOT
+    create(:closed_issue,
+           title: 'Tasks-closed',
+           project: project,
+           author: project.users.first,
+           description: desc_text
+          )
+  end
+
   step 'empty project "Empty Project"' do
     create :empty_project, name: 'Empty Project', namespace: @user.namespace
   end
diff --git a/features/steps/project/merge_requests.rb b/features/steps/project/merge_requests.rb
index fba03c2fc64..0fec2604915 100644
--- a/features/steps/project/merge_requests.rb
+++ b/features/steps/project/merge_requests.rb
@@ -97,6 +97,20 @@ class Spinach::Features::ProjectMergeRequests < Spinach::FeatureSteps
            author: project.users.first)
   end
 
+  step 'project "Shop" has "MR-task-open" open MR with task markdown' do
+    desc_text = <<EOT.gsub(/^ {6}/, '')
+      * [ ] Task 1
+      * [x] Task 2
+EOT
+    create(:merge_request,
+           title: 'MR-task-open',
+           source_project: project,
+           target_project: project,
+           author: project.users.first,
+           description: desc_text
+          )
+  end
+
   step 'I switch to the diff tab' do
     visit diffs_project_merge_request_path(project, merge_request)
   end
diff --git a/features/steps/shared/markdown.rb b/features/steps/shared/markdown.rb
index 092f2fceb57..1d9058cf256 100644
--- a/features/steps/shared/markdown.rb
+++ b/features/steps/shared/markdown.rb
@@ -9,4 +9,34 @@ module SharedMarkdown
   step 'Header "Description header" should have correct id and link' do
     header_should_have_correct_id_and_link(1, 'Description header', 'description-header')
   end
+
+  step 'I should see task checkboxes in the description' do
+    expect(page).to have_selector(
+      'div.description li.task-list-item input[type="checkbox"]'
+    )
+  end
+
+  step 'I should see the task status for issue "Tasks-open"' do
+    expect(find(:css, 'span.task-status').text).to eq(
+      '2 tasks (1 done, 1 unfinished)'
+    )
+  end
+
+  step 'I should see the task status for merge request "MR-task-open"' do
+    expect(find(:css, 'span.task-status').text).to eq(
+      '2 tasks (1 done, 1 unfinished)'
+    )
+  end
+
+  step 'Task checkboxes should be enabled' do
+    expect(page).to have_selector(
+      'div.description li.task-list-item input[type="checkbox"]:enabled'
+    )
+  end
+
+  step 'Task checkboxes should be disabled' do
+    expect(page).to have_selector(
+      'div.description li.task-list-item input[type="checkbox"]:disabled'
+    )
+  end
 end
diff --git a/features/steps/shared/note.rb b/features/steps/shared/note.rb
index 4019fe3697a..2b2cb47a715 100644
--- a/features/steps/shared/note.rb
+++ b/features/steps/shared/note.rb
@@ -119,4 +119,18 @@ module SharedNote
       page.should_not have_css("#comment-with-a-header")
     end
   end
+
+  step 'I leave a comment with task markdown' do
+    within('.js-main-target-form') do
+      fill_in 'note[note]', with: '* [x] Task item'
+      click_button 'Add Comment'
+      sleep 0.05
+    end
+  end
+
+  step 'I should not see task checkboxes in the comment' do
+    expect(page).not_to have_selector(
+      'li.note div.timeline-content input[type="checkbox"]'
+    )
+  end
 end
diff --git a/features/steps/shared/paths.rb b/features/steps/shared/paths.rb
index 141ff13b67d..1f238f8befd 100644
--- a/features/steps/shared/paths.rb
+++ b/features/steps/shared/paths.rb
@@ -292,6 +292,16 @@ module SharedPaths
     visit project_issue_path(issue.project, issue)
   end
 
+  step 'I visit issue page "Tasks-open"' do
+    issue = Issue.find_by(title: 'Tasks-open')
+    visit project_issue_path(issue.project, issue)
+  end
+
+  step 'I visit issue page "Tasks-closed"' do
+    issue = Issue.find_by(title: 'Tasks-closed')
+    visit project_issue_path(issue.project, issue)
+  end
+
   step 'I visit project "Shop" labels page' do
     project = Project.find_by(name: 'Shop')
     visit project_labels_path(project)
@@ -322,6 +332,16 @@ module SharedPaths
     visit project_merge_request_path(mr.target_project, mr)
   end
 
+  step 'I visit merge request page "MR-task-open"' do
+    mr = MergeRequest.find_by(title: 'MR-task-open')
+    visit project_merge_request_path(mr.target_project, mr)
+  end
+
+  step 'I visit merge request page "MR-task-closed"' do
+    mr = MergeRequest.find_by(title: 'MR-task-closed')
+    visit project_merge_request_path(mr.target_project, mr)
+  end
+
   step 'I visit project "Shop" merge requests page' do
     visit project_merge_requests_path(project)
   end
diff --git a/lib/gitlab/markdown.rb b/lib/gitlab/markdown.rb
index 709a74fe21e..17512a51658 100644
--- a/lib/gitlab/markdown.rb
+++ b/lib/gitlab/markdown.rb
@@ -33,6 +33,11 @@ module Gitlab
 
     attr_reader :html_options
 
+    def gfm_with_tasks(text, project = @project, html_options = {})
+      text = gfm(text, project, html_options)
+      parse_tasks(text)
+    end
+
     # Public: Parse the provided text with GitLab-Flavored Markdown
     #
     # text         - the source text
@@ -265,5 +270,24 @@ module Gitlab
       )
       link_to("#{prefix_text}##{identifier}", url, options)
     end
+
+    # Turn list items that start with "[ ]" into HTML checkbox inputs.
+    def parse_tasks(text)
+      li_tag = '<li class="task-list-item">'
+      unchecked_box = '<input type="checkbox" value="on" disabled />'
+      checked_box = unchecked_box.sub(/\/>$/, 'checked="checked" />')
+
+      # Regexp captures don't seem to work when +text+ is an
+      # ActiveSupport::SafeBuffer, hence the `String.new`
+      String.new(text).gsub(Taskable::TASK_PATTERN_HTML) do
+        checked = $LAST_MATCH_INFO[:checked].downcase == 'x'
+
+        if checked
+          "#{li_tag}#{checked_box}"
+        else
+          "#{li_tag}#{unchecked_box}"
+        end
+      end
+    end
   end
 end
diff --git a/lib/redcarpet/render/gitlab_html.rb b/lib/redcarpet/render/gitlab_html.rb
index bb225f1acd8..c3378d6a18f 100644
--- a/lib/redcarpet/render/gitlab_html.rb
+++ b/lib/redcarpet/render/gitlab_html.rb
@@ -47,6 +47,10 @@ class Redcarpet::Render::GitlabHTML < Redcarpet::Render::HTML
     unless @template.instance_variable_get("@project_wiki") || @project.nil?
       full_document = h.create_relative_links(full_document)
     end
-    h.gfm(full_document)
+    if @options[:parse_tasks]
+      h.gfm_with_tasks(full_document)
+    else
+      h.gfm(full_document)
+    end
   end
 end
diff --git a/spec/helpers/gitlab_markdown_helper_spec.rb b/spec/helpers/gitlab_markdown_helper_spec.rb
index 73b3d91e96e..15033f07432 100644
--- a/spec/helpers/gitlab_markdown_helper_spec.rb
+++ b/spec/helpers/gitlab_markdown_helper_spec.rb
@@ -616,7 +616,7 @@ describe GitlabMarkdownHelper do
     end
   end
 
-  describe "markdwon for empty repository" do
+  describe 'markdown for empty repository' do
     before do
       @project = empty_project
       @repository = empty_project.repository
@@ -652,4 +652,103 @@ describe GitlabMarkdownHelper do
       helper.render_wiki_content(@wiki)
     end
   end
+
+  describe '#gfm_with_tasks' do
+    before(:all) do
+      @source_text_asterisk = <<EOT.gsub(/^\s{8}/, '')
+        * [ ] valid unchecked task
+        * [x] valid lowercase checked task
+        * [X] valid uppercase checked task
+            * [ ] valid unchecked nested task
+            * [x] valid checked nested task
+
+        [ ] not an unchecked task - no list item
+        [x] not a checked task - no list item
+
+        * [  ] not an unchecked task - too many spaces
+        * [x ] not a checked task - too many spaces
+        * [] not an unchecked task - no spaces
+        * Not a task [ ] - not at beginning
+EOT
+
+      @source_text_dash = <<EOT.gsub(/^\s{8}/, '')
+        - [ ] valid unchecked task
+        - [x] valid lowercase checked task
+        - [X] valid uppercase checked task
+            - [ ] valid unchecked nested task
+            - [x] valid checked nested task
+EOT
+    end
+
+    it 'should render checkboxes at beginning of asterisk list items' do
+      rendered_text = markdown(@source_text_asterisk, parse_tasks: true)
+
+      expect(rendered_text).to match(/<input.*checkbox.*valid unchecked task/)
+      expect(rendered_text).to match(
+        /<input.*checkbox.*valid lowercase checked task/
+      )
+      expect(rendered_text).to match(
+        /<input.*checkbox.*valid uppercase checked task/
+      )
+    end
+
+    it 'should render checkboxes at beginning of dash list items' do
+      rendered_text = markdown(@source_text_dash, parse_tasks: true)
+
+      expect(rendered_text).to match(/<input.*checkbox.*valid unchecked task/)
+      expect(rendered_text).to match(
+        /<input.*checkbox.*valid lowercase checked task/
+      )
+      expect(rendered_text).to match(
+        /<input.*checkbox.*valid uppercase checked task/
+      )
+    end
+
+    it 'should not be confused by whitespace before bullets' do
+      rendered_text_asterisk = markdown(@source_text_asterisk,
+                                        parse_tasks: true)
+      rendered_text_dash = markdown(@source_text_dash, parse_tasks: true)
+
+      expect(rendered_text_asterisk).to match(
+        /<input.*checkbox.*valid unchecked nested task/
+      )
+      expect(rendered_text_asterisk).to match(
+        /<input.*checkbox.*valid checked nested task/
+      )
+      expect(rendered_text_dash).to match(
+        /<input.*checkbox.*valid unchecked nested task/
+      )
+      expect(rendered_text_dash).to match(
+        /<input.*checkbox.*valid checked nested task/
+      )
+    end
+
+    it 'should not render checkboxes outside of list items' do
+      rendered_text = markdown(@source_text_asterisk, parse_tasks: true)
+
+      expect(rendered_text).not_to match(
+        /<input.*checkbox.*not an unchecked task - no list item/
+      )
+      expect(rendered_text).not_to match(
+        /<input.*checkbox.*not a checked task - no list item/
+      )
+    end
+
+    it 'should not render checkboxes with invalid formatting' do
+      rendered_text = markdown(@source_text_asterisk, parse_tasks: true)
+
+      expect(rendered_text).not_to match(
+        /<input.*checkbox.*not an unchecked task - too many spaces/
+      )
+      expect(rendered_text).not_to match(
+        /<input.*checkbox.*not a checked task - too many spaces/
+      )
+      expect(rendered_text).not_to match(
+        /<input.*checkbox.*not an unchecked task - no spaces/
+      )
+      expect(rendered_text).not_to match(
+        /Not a task.*<input.*checkbox.*not at beginning/
+      )
+    end
+  end
 end
diff --git a/spec/models/issue_spec.rb b/spec/models/issue_spec.rb
index 8b299cea67c..6b6efe832e5 100644
--- a/spec/models/issue_spec.rb
+++ b/spec/models/issue_spec.rb
@@ -60,4 +60,8 @@ describe Issue do
     let(:backref_text) { "issue ##{subject.iid}" }
     let(:set_mentionable_text) { ->(txt){ subject.description = txt } }
   end
+
+  it_behaves_like 'a Taskable' do
+    let(:subject) { create :issue }
+  end
 end
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index c40f75290ed..7b0d261d72f 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -119,4 +119,8 @@ describe MergeRequest do
     let(:backref_text) { "merge request !#{subject.iid}" }
     let(:set_mentionable_text) { ->(txt){ subject.title = txt } }
   end
+
+  it_behaves_like 'a Taskable' do
+    let(:subject) { create :merge_request, :simple }
+  end
 end
diff --git a/spec/support/taskable_shared_examples.rb b/spec/support/taskable_shared_examples.rb
new file mode 100644
index 00000000000..42252675683
--- /dev/null
+++ b/spec/support/taskable_shared_examples.rb
@@ -0,0 +1,42 @@
+# Specs for task state functionality for issues and merge requests.
+#
+# Requires a context containing:
+#   let(:subject) { Issue or MergeRequest }
+shared_examples 'a Taskable' do
+  before do
+    subject.description = <<EOT.gsub(/ {6}/, '')
+      * [ ] Task 1
+      * [x] Task 2
+      * [x] Task 3
+      * [ ] Task 4
+      * [ ] Task 5
+EOT
+  end
+
+  it 'updates the Nth task correctly' do
+    subject.update_nth_task(1, true)
+    expect(subject.description).to match(/\[x\] Task 1/)
+
+    subject.update_nth_task(2, true)
+    expect(subject.description).to match('\[x\] Task 2')
+
+    subject.update_nth_task(3, false)
+    expect(subject.description).to match('\[ \] Task 3')
+
+    subject.update_nth_task(4, false)
+    expect(subject.description).to match('\[ \] Task 4')
+  end
+
+  it 'returns the correct task status' do
+    expect(subject.task_status).to match('5 tasks')
+    expect(subject.task_status).to match('2 done')
+    expect(subject.task_status).to match('3 unfinished')
+  end
+
+  it 'knows if it has tasks' do
+    expect(subject.tasks?).to be_true
+
+    subject.description = 'Now I have no tasks'
+    expect(subject.tasks?).to be_false
+  end
+end