Remove Redcarpet markdown engine

This engine was replaced with CommonMarker in 11.4, it was deprecated
since then.

58 files changed, 148 insertions, 699 deletions

diff --git a/Gemfile b/Gemfile
index 95cb9671a61..322b5951973 100644
--- a/Gemfile
+++ b/Gemfile
@@ -116,7 +116,6 @@ gem 'html-pipeline', '~> 2.8'
 gem 'deckar01-task_list', '2.2.0'
 gem 'gitlab-markup', '~> 1.6.5'
 gem 'github-markup', '~> 1.7.0', require: 'github/markup'
-gem 'redcarpet', '~> 3.4'
 gem 'commonmarker', '~> 0.17'
 gem 'RedCloth', '~> 4.3.2'
 gem 'rdoc', '~> 6.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index e6b563b5cb8..a9244fd853c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -682,7 +682,6 @@ GEM
     recaptcha (3.0.0)
       json
     recursive-open-struct (1.1.0)
-    redcarpet (3.4.0)
     redis (3.3.5)
     redis-actionpack (5.0.2)
       actionpack (>= 4.0, < 6)
@@ -1118,7 +1117,6 @@ DEPENDENCIES
   rdoc (~> 6.0)
   re2 (~> 1.1.1)
   recaptcha (~> 3.0)
-  redcarpet (~> 3.4)
   redis (~> 3.2)
   redis-namespace (~> 1.6.0)
   redis-rails (~> 5.0.2)
diff --git a/app/assets/javascripts/behaviors/preview_markdown.js b/app/assets/javascripts/behaviors/preview_markdown.js
index 35f1bb6b080..7adccbb062f 100644
--- a/app/assets/javascripts/behaviors/preview_markdown.js
+++ b/app/assets/javascripts/behaviors/preview_markdown.js
@@ -28,16 +28,13 @@ MarkdownPreview.prototype.ajaxCache = {};
 
 MarkdownPreview.prototype.showPreview = function($form) {
   var mdText;
-  var markdownVersion;
-  var url;
   var preview = $form.find('.js-md-preview');
+  var url = preview.data('url');
   if (preview.hasClass('md-preview-loading')) {
     return;
   }
 
   mdText = $form.find('textarea.markdown-area').val();
-  markdownVersion = $form.attr('data-markdown-version');
-  url = this.versionedPreviewPath(preview.data('url'), markdownVersion);
 
   if (mdText.trim().length === 0) {
     preview.text(this.emptyMessage);
@@ -67,16 +64,6 @@ MarkdownPreview.prototype.showPreview = function($form) {
   }
 };
 
-MarkdownPreview.prototype.versionedPreviewPath = function(markdownPreviewPath, markdownVersion) {
-  if (typeof markdownVersion === 'undefined') {
-    return markdownPreviewPath;
-  }
-
-  return `${markdownPreviewPath}${
-    markdownPreviewPath.indexOf('?') === -1 ? '?' : '&'
-  }markdown_version=${markdownVersion}`;
-};
-
 MarkdownPreview.prototype.fetchMarkdownPreview = function(text, url, success) {
   if (!url) {
     return;
diff --git a/app/assets/javascripts/issue_show/components/app.vue b/app/assets/javascripts/issue_show/components/app.vue
index fea7f0d77a5..bd757a76ee7 100644
--- a/app/assets/javascripts/issue_show/components/app.vue
+++ b/app/assets/javascripts/issue_show/components/app.vue
@@ -108,11 +108,6 @@ export default {
       type: String,
       required: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     projectPath: {
       type: String,
       required: true,
@@ -313,7 +308,6 @@ export default {
         :issuable-templates="issuableTemplates"
         :markdown-docs-path="markdownDocsPath"
         :markdown-preview-path="markdownPreviewPath"
-        :markdown-version="markdownVersion"
         :project-path="projectPath"
         :project-namespace="projectNamespace"
         :show-delete-button="showDeleteButton"
diff --git a/app/assets/javascripts/issue_show/components/fields/description.vue b/app/assets/javascripts/issue_show/components/fields/description.vue
index 90258c0e044..299130e56ae 100644
--- a/app/assets/javascripts/issue_show/components/fields/description.vue
+++ b/app/assets/javascripts/issue_show/components/fields/description.vue
@@ -20,11 +20,6 @@ export default {
       type: String,
       required: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     canAttachFile: {
       type: Boolean,
       required: false,
@@ -48,7 +43,6 @@ export default {
     <markdown-field
       :markdown-preview-path="markdownPreviewPath"
       :markdown-docs-path="markdownDocsPath"
-      :markdown-version="markdownVersion"
       :can-attach-file="canAttachFile"
       :enable-autocomplete="enableAutocomplete"
     >
diff --git a/app/assets/javascripts/issue_show/components/form.vue b/app/assets/javascripts/issue_show/components/form.vue
index 45b60bc3392..eade31f1d14 100644
--- a/app/assets/javascripts/issue_show/components/form.vue
+++ b/app/assets/javascripts/issue_show/components/form.vue
@@ -39,11 +39,6 @@ export default {
       type: String,
       required: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     projectPath: {
       type: String,
       required: true,
@@ -101,7 +96,6 @@ export default {
       :form-state="formState"
       :markdown-preview-path="markdownPreviewPath"
       :markdown-docs-path="markdownDocsPath"
-      :markdown-version="markdownVersion"
       :can-attach-file="canAttachFile"
       :enable-autocomplete="enableAutocomplete"
     />
diff --git a/app/assets/javascripts/notes.js b/app/assets/javascripts/notes.js
index c3443c300e3..c9c01354333 100644
--- a/app/assets/javascripts/notes.js
+++ b/app/assets/javascripts/notes.js
@@ -1239,15 +1239,13 @@ export default class Notes {
     var postUrl = $originalContentEl.data('postUrl');
     var targetId = $originalContentEl.data('targetId');
     var targetType = $originalContentEl.data('targetType');
-    var markdownVersion = $originalContentEl.data('markdownVersion');
 
     this.glForm = new GLForm($editForm.find('form'), this.enableGFM);
 
     $editForm
       .find('form')
       .attr('action', `${postUrl}?html=true`)
-      .attr('data-remote', 'true')
-      .attr('data-markdown-version', markdownVersion);
+      .attr('data-remote', 'true');
     $editForm.find('.js-form-target-id').val(targetId);
     $editForm.find('.js-form-target-type').val(targetType);
     $editForm
diff --git a/app/assets/javascripts/notes/components/comment_form.vue b/app/assets/javascripts/notes/components/comment_form.vue
index d669ba5a8fa..1d6cb9485f7 100644
--- a/app/assets/javascripts/notes/components/comment_form.vue
+++ b/app/assets/javascripts/notes/components/comment_form.vue
@@ -39,11 +39,6 @@ export default {
       type: String,
       required: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
   },
   data() {
     return {
@@ -342,7 +337,6 @@ Please check your network connection and try again.`;
               :markdown-preview-path="markdownPreviewPath"
               :markdown-docs-path="markdownDocsPath"
               :quick-actions-docs-path="quickActionsDocsPath"
-              :markdown-version="markdownVersion"
               :add-spacing-classes="false"
             >
               <textarea
diff --git a/app/assets/javascripts/notes/components/note_body.vue b/app/assets/javascripts/notes/components/note_body.vue
index bcf5d334da4..ff303d0f55a 100644
--- a/app/assets/javascripts/notes/components/note_body.vue
+++ b/app/assets/javascripts/notes/components/note_body.vue
@@ -111,7 +111,6 @@ export default {
       :line="line"
       :note="note"
       :help-page-path="helpPagePath"
-      :markdown-version="note.cached_markdown_version"
       @handleFormUpdate="handleFormUpdate"
       @cancelForm="formCancelHandler"
     />
diff --git a/app/assets/javascripts/notes/components/note_form.vue b/app/assets/javascripts/notes/components/note_form.vue
index 269b4a4b117..92258a25438 100644
--- a/app/assets/javascripts/notes/components/note_form.vue
+++ b/app/assets/javascripts/notes/components/note_form.vue
@@ -26,11 +26,6 @@ export default {
       required: false,
       default: '',
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     saveButtonTitle: {
       type: String,
       required: false,
@@ -202,7 +197,6 @@ export default {
       <markdown-field
         :markdown-preview-path="markdownPreviewPath"
         :markdown-docs-path="markdownDocsPath"
-        :markdown-version="markdownVersion"
         :quick-actions-docs-path="quickActionsDocsPath"
         :line="line"
         :note="discussionNote"
diff --git a/app/assets/javascripts/notes/components/notes_app.vue b/app/assets/javascripts/notes/components/notes_app.vue
index f3fcfdfda05..5edceea043c 100644
--- a/app/assets/javascripts/notes/components/notes_app.vue
+++ b/app/assets/javascripts/notes/components/notes_app.vue
@@ -44,11 +44,6 @@ export default {
       required: false,
       default: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     helpPagePath: {
       type: String,
       required: false,
@@ -216,10 +211,6 @@ export default {
       </template>
     </ul>
 
-    <comment-form
-      v-if="!commentsDisabled"
-      :noteable-type="noteableType"
-      :markdown-version="markdownVersion"
-    />
+    <comment-form v-if="!commentsDisabled" :noteable-type="noteableType" />
   </div>
 </template>
diff --git a/app/assets/javascripts/notes/index.js b/app/assets/javascripts/notes/index.js
index 2f715c85fa6..4883266dae5 100644
--- a/app/assets/javascripts/notes/index.js
+++ b/app/assets/javascripts/notes/index.js
@@ -18,7 +18,6 @@ document.addEventListener('DOMContentLoaded', () => {
       const notesDataset = document.getElementById('js-vue-notes').dataset;
       const parsedUserData = JSON.parse(notesDataset.currentUserData);
       const noteableData = JSON.parse(notesDataset.noteableData);
-      const markdownVersion = parseInt(notesDataset.markdownVersion, 10);
       let currentUserData = {};
 
       noteableData.noteableType = notesDataset.noteableType;
@@ -37,7 +36,6 @@ document.addEventListener('DOMContentLoaded', () => {
       return {
         noteableData,
         currentUserData,
-        markdownVersion,
         notesData: JSON.parse(notesDataset.notesData),
       };
     },
@@ -47,7 +45,6 @@ document.addEventListener('DOMContentLoaded', () => {
           noteableData: this.noteableData,
           notesData: this.notesData,
           userData: this.currentUserData,
-          markdownVersion: this.markdownVersion,
         },
       });
     },
diff --git a/app/assets/javascripts/vue_shared/components/markdown/field.vue b/app/assets/javascripts/vue_shared/components/markdown/field.vue
index cc07ef46064..3f607aa2a0a 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/field.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/field.vue
@@ -27,11 +27,6 @@ export default {
       type: String,
       required: true,
     },
-    markdownVersion: {
-      type: Number,
-      required: false,
-      default: 0,
-    },
     addSpacingClasses: {
       type: Boolean,
       required: false,
@@ -158,7 +153,7 @@ export default {
         this.markdownPreviewLoading = true;
         this.markdownPreview = __('Loading…');
         this.$http
-          .post(this.versionedPreviewPath(), { text })
+          .post(this.markdownPreviewPath, { text })
           .then(resp => resp.json())
           .then(data => this.renderMarkdown(data))
           .catch(() => new Flash(__('Error loading markdown preview')));
@@ -186,13 +181,6 @@ export default {
         .then(() => $(this.$refs['markdown-preview']).renderGFM())
         .catch(() => new Flash(__('Error rendering markdown preview')));
     },
-
-    versionedPreviewPath() {
-      const { markdownPreviewPath, markdownVersion } = this;
-      return `${markdownPreviewPath}${
-        markdownPreviewPath.indexOf('?') === -1 ? '?' : '&'
-      }markdown_version=${markdownVersion}`;
-    },
   },
 };
 </script>
diff --git a/app/controllers/concerns/preview_markdown.rb b/app/controllers/concerns/preview_markdown.rb
index 4b0f0b8255c..f72d25fc54c 100644
--- a/app/controllers/concerns/preview_markdown.rb
+++ b/app/controllers/concerns/preview_markdown.rb
@@ -16,8 +16,6 @@ module PreviewMarkdown
       else {}
       end
 
-    markdown_params[:markdown_engine] = result[:markdown_engine]
-
     render json: {
       body: view_context.markdown(result[:text], markdown_params),
       references: {
diff --git a/app/helpers/issuables_helper.rb b/app/helpers/issuables_helper.rb
index 0fee29bf7c7..1a471034972 100644
--- a/app/helpers/issuables_helper.rb
+++ b/app/helpers/issuables_helper.rb
@@ -268,7 +268,6 @@ module IssuablesHelper
       issuableRef: issuable.to_reference,
       markdownPreviewPath: preview_markdown_path(parent),
       markdownDocsPath: help_page_path('user/markdown'),
-      markdownVersion: issuable.cached_markdown_version,
       lockVersion: issuable.lock_version,
       issuableTemplates: issuable_templates(issuable),
       initialTitleHtml: markdown_field(issuable, :title),
diff --git a/app/helpers/markup_helper.rb b/app/helpers/markup_helper.rb
index 0d638b850b4..66f4b7b3f30 100644
--- a/app/helpers/markup_helper.rb
+++ b/app/helpers/markup_helper.rb
@@ -116,7 +116,6 @@ module MarkupHelper
 
   def markup(file_name, text, context = {})
     context[:project] ||= @project
-    context[:markdown_engine] ||= :redcarpet unless commonmark_for_repositories_enabled?
     html = context.delete(:rendered) || markup_unsafe(file_name, text, context)
     prepare_for_rendering(html, context)
   end
@@ -132,7 +131,6 @@ module MarkupHelper
       page_slug: wiki_page.slug,
       issuable_state_filter_enabled: true
     )
-    context[:markdown_engine] ||= :redcarpet unless commonmark_for_repositories_enabled?
 
     html =
       case wiki_page.format
@@ -187,10 +185,6 @@ module MarkupHelper
     end
   end
 
-  def commonmark_for_repositories_enabled?
-    Feature.enabled?(:commonmark_for_repositories, default_enabled: true)
-  end
-
   private
 
   # Return +text+, truncated to +max_chars+ characters, excluding any HTML
diff --git a/app/helpers/notes_helper.rb b/app/helpers/notes_helper.rb
index 293dd20ad49..aaf38cbfe70 100644
--- a/app/helpers/notes_helper.rb
+++ b/app/helpers/notes_helper.rb
@@ -171,7 +171,6 @@ module NotesHelper
       registerPath: new_session_path(:user, redirect_to_referer: 'yes', anchor: 'register-pane'),
       newSessionPath: new_session_path(:user, redirect_to_referer: 'yes'),
       markdownDocsPath: help_page_path('user/markdown'),
-      markdownVersion: issuable.cached_markdown_version,
       quickActionsDocsPath: help_page_path('user/project/quick_actions'),
       closePath: close_issuable_path(issuable),
       reopenPath: reopen_issuable_path(issuable),
diff --git a/app/helpers/projects_helper.rb b/app/helpers/projects_helper.rb
index 85248a16f50..e1d6e22b90b 100644
--- a/app/helpers/projects_helper.rb
+++ b/app/helpers/projects_helper.rb
@@ -265,10 +265,6 @@ module ProjectsHelper
     link_to 'BFG', 'https://rtyley.github.io/bfg-repo-cleaner/', target: '_blank', rel: 'noopener noreferrer'
   end
 
-  def legacy_render_context(params)
-    params[:legacy_render] ? { markdown_engine: :redcarpet } : {}
-  end
-
   def explore_projects_tab?
     current_page?(explore_projects_path) ||
       current_page?(trending_explore_projects_path) ||
diff --git a/app/models/concerns/cache_markdown_field.rb b/app/models/concerns/cache_markdown_field.rb
index 588204c7470..5fa6f79bdaa 100644
--- a/app/models/concerns/cache_markdown_field.rb
+++ b/app/models/concerns/cache_markdown_field.rb
@@ -13,7 +13,6 @@ module CacheMarkdownField
   extend ActiveSupport::Concern
 
   # Increment this number every time the renderer changes its output
-  CACHE_REDCARPET_VERSION         = 3
   CACHE_COMMONMARK_VERSION_START  = 10
   CACHE_COMMONMARK_VERSION        = 14
 
@@ -42,18 +41,6 @@ module CacheMarkdownField
     end
   end
 
-  class MarkdownEngine
-    def self.from_version(version = nil)
-      return :common_mark if version.nil? || version == 0
-
-      if version < CacheMarkdownField::CACHE_COMMONMARK_VERSION_START
-        :redcarpet
-      else
-        :common_mark
-      end
-    end
-  end
-
   def skip_project_check?
     false
   end
@@ -71,7 +58,7 @@ module CacheMarkdownField
     # Banzai is less strict about authors, so don't always have an author key
     context[:author] = self.author if self.respond_to?(:author)
 
-    context[:markdown_engine] = MarkdownEngine.from_version(latest_cached_markdown_version)
+    context[:markdown_engine] = :common_mark
 
     context
   end
@@ -128,17 +115,7 @@ module CacheMarkdownField
   end
 
   def latest_cached_markdown_version
-    return CacheMarkdownField::CACHE_COMMONMARK_VERSION unless cached_markdown_version
-
-    if legacy_markdown?
-      CacheMarkdownField::CACHE_REDCARPET_VERSION
-    else
-      CacheMarkdownField::CACHE_COMMONMARK_VERSION
-    end
-  end
-
-  def legacy_markdown?
-    cached_markdown_version && cached_markdown_version.between?(1, CacheMarkdownField::CACHE_COMMONMARK_VERSION_START - 1)
+    CacheMarkdownField::CACHE_COMMONMARK_VERSION
   end
 
   included do
diff --git a/app/models/repository.rb b/app/models/repository.rb
index e6ab3b484a2..9ae13fbaa80 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -614,7 +614,6 @@ class Repository
     return unless readme
 
     context = { project: project }
-    context[:markdown_engine] = :redcarpet unless MarkupHelper.commonmark_for_repositories_enabled?
 
     MarkupHelper.markup_unsafe(readme.name, readme.data, context)
   end
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index 842d59d26a0..ef991eaf234 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -270,9 +270,7 @@ class IssuableBaseService < BaseService
     tasklist_toggler = TaskListToggleService.new(issuable.description, issuable.description_html,
                                                  line_source: update_task_params[:line_source],
                                                  line_number: update_task_params[:line_number].to_i,
-                                                 toggle_as_checked: update_task_params[:checked],
-                                                 index: update_task_params[:index].to_i,
-                                                 sourcepos: !issuable.legacy_markdown?)
+                                                 toggle_as_checked: update_task_params[:checked])
 
     unless tasklist_toggler.execute
       # if we make it here, the data is much newer than we thought it was - fail fast
diff --git a/app/services/preview_markdown_service.rb b/app/services/preview_markdown_service.rb
index a449a5dc3e9..c1655c38095 100644
--- a/app/services/preview_markdown_service.rb
+++ b/app/services/preview_markdown_service.rb
@@ -10,8 +10,7 @@ class PreviewMarkdownService < BaseService
       text: text,
       users: users,
       suggestions: suggestions,
-      commands: commands.join(' '),
-      markdown_engine: markdown_engine
+      commands: commands.join(' ')
     )
   end
 
@@ -49,12 +48,4 @@ class PreviewMarkdownService < BaseService
   def commands_target_id
     params[:quick_actions_target_id]
   end
-
-  def markdown_engine
-    if params[:legacy_render]
-      :redcarpet
-    else
-      CacheMarkdownField::MarkdownEngine.from_version(params[:markdown_version].to_i)
-    end
-  end
 end
diff --git a/app/services/task_list_toggle_service.rb b/app/services/task_list_toggle_service.rb
index 2717fc9035a..b5c4cd3235d 100644
--- a/app/services/task_list_toggle_service.rb
+++ b/app/services/task_list_toggle_service.rb
@@ -5,17 +5,13 @@
 # We don't care if the text has changed above or below the specific checkbox, as long
 # the checkbox still exists at exactly the same line number and the text is equal.
 # If successful, new values are available in `updated_markdown` and `updated_markdown_html`
-#
-# Note: once we've removed RedCarpet support, we can remove the `index` and `sourcepos`
-# parameters
 class TaskListToggleService
   attr_reader :updated_markdown, :updated_markdown_html
 
-  def initialize(markdown, markdown_html, line_source:, line_number:, toggle_as_checked:, index:, sourcepos: true)
+  def initialize(markdown, markdown_html, line_source:, line_number:, toggle_as_checked:)
     @markdown, @markdown_html  = markdown, markdown_html
     @line_source, @line_number = line_source, line_number
     @toggle_as_checked         = toggle_as_checked
-    @index, @use_sourcepos     = index, sourcepos
 
     @updated_markdown, @updated_markdown_html = nil
   end
@@ -28,8 +24,8 @@ class TaskListToggleService
 
   private
 
-  attr_reader :markdown, :markdown_html, :index, :toggle_as_checked
-  attr_reader :line_source, :line_number, :use_sourcepos
+  attr_reader :markdown, :markdown_html, :toggle_as_checked
+  attr_reader :line_source, :line_number
 
   def toggle_markdown
     source_lines      = markdown.split("\n")
@@ -68,17 +64,8 @@ class TaskListToggleService
   end
 
   # When using CommonMark, we should be able to use the embedded `sourcepos` attribute to
-  # target the exact line in the DOM.  For RedCarpet, we need to use the index of the checkbox
-  # that was checked and match it with what we think is the same checkbox.
-  # The reason `sourcepos` is slightly more reliable is the case where a line of text is
-  # changed from a regular line into a checkbox (or vice versa).  Then the checked index
-  # in the UI will be off from the list of checkboxes we've calculated locally.
-  # It's a rare circumstance, but since we can account for it, we do.
+  # target the exact line in the DOM.
   def get_html_checkbox(html)
-    if use_sourcepos
-      html.css(".task-list-item[data-sourcepos^='#{line_number}:'] > input.task-list-item-checkbox").first
-    else
-      html.css('.task-list-item-checkbox')[index - 1]
-    end
+    html.css(".task-list-item[data-sourcepos^='#{line_number}:'] > input.task-list-item-checkbox").first
   end
 end
diff --git a/app/views/projects/_wiki.html.haml b/app/views/projects/_wiki.html.haml
index 45e1d32980c..de4653dad2c 100644
--- a/app/views/projects/_wiki.html.haml
+++ b/app/views/projects/_wiki.html.haml
@@ -2,7 +2,7 @@
   %div{ class: container_class }
     .prepend-top-default.append-bottom-default
       .wiki
-        = render_wiki_content(@wiki_home, legacy_render_context(params))
+        = render_wiki_content(@wiki_home)
 - else
   - can_create_wiki = can?(current_user, :create_wiki, @project)
   .landing{ class: [('row-content-block row p-0 align-items-center' if can_create_wiki), ('content-block' unless can_create_wiki)] }
diff --git a/app/views/projects/blob/edit.html.haml b/app/views/projects/blob/edit.html.haml
index 3f2d96b70e5..4520cca8cf5 100644
--- a/app/views/projects/blob/edit.html.haml
+++ b/app/views/projects/blob/edit.html.haml
@@ -21,7 +21,7 @@
           Write
 
       %li
-        = link_to '#preview', 'data-preview-url' => project_preview_blob_path(@project, @id, legacy_render: params[:legacy_render]) do
+        = link_to '#preview', 'data-preview-url' => project_preview_blob_path(@project, @id) do
           = editing_preview_title(@blob.name)
 
     = form_tag(project_update_blob_path(@project, @id), method: :put, class: 'js-quick-submit js-requires-input js-edit-blob-form', data: blob_editor_paths(@project)) do
diff --git a/app/views/projects/blob/preview.html.haml b/app/views/projects/blob/preview.html.haml
index ff460a3831c..66687f087ff 100644
--- a/app/views/projects/blob/preview.html.haml
+++ b/app/views/projects/blob/preview.html.haml
@@ -2,7 +2,7 @@
   .diff-content
     - if markup?(@blob.name)
       .file-content.wiki.md{ class: ('use-csslab' if Feature.enabled?(:csslab)) }
-        = markup(@blob.name, @content, legacy_render_context(params))
+        = markup(@blob.name, @content)
     - else
       .file-content.code.js-syntax-highlight
         - unless @diff_lines.empty?
diff --git a/app/views/projects/blob/viewers/_markup.html.haml b/app/views/projects/blob/viewers/_markup.html.haml
index 6edbfd91b21..1a77eb078be 100644
--- a/app/views/projects/blob/viewers/_markup.html.haml
+++ b/app/views/projects/blob/viewers/_markup.html.haml
@@ -1,6 +1,4 @@
 - blob = viewer.blob
-- context = legacy_render_context(params)
-- unless context[:markdown_engine] == :redcarpet
-  - context[:rendered] = blob.rendered_markup if blob.respond_to?(:rendered_markup)
+- context = blob.respond_to?(:rendered_markup) ? { rendered: blob.rendered_markup } : {}
 .file-content.wiki.md{ class: ('use-csslab' if Feature.enabled?(:csslab)) }
   = markup(blob.name, blob.data, context)
diff --git a/app/views/projects/issues/_form.html.haml b/app/views/projects/issues/_form.html.haml
index 1e4e9450ffa..1be1087b36f 100644
--- a/app/views/projects/issues/_form.html.haml
+++ b/app/views/projects/issues/_form.html.haml
@@ -1,4 +1,3 @@
 = form_for [@project.namespace.becomes(Namespace), @project, @issue],
-           html: { class: 'issue-form common-note-form js-quick-submit js-requires-input' },
-           data: { markdown_version: @issue.cached_markdown_version } do |f|
+           html: { class: 'issue-form common-note-form js-quick-submit js-requires-input' } do |f|
   = render 'shared/issuable/form', f: f, issuable: @issue
diff --git a/app/views/projects/merge_requests/_form.html.haml b/app/views/projects/merge_requests/_form.html.haml
index 13b967beba1..a7c9e54506d 100644
--- a/app/views/projects/merge_requests/_form.html.haml
+++ b/app/views/projects/merge_requests/_form.html.haml
@@ -1,4 +1,3 @@
 = form_for [@project.namespace.becomes(Namespace), @project, @merge_request],
-           html: { class: 'merge-request-form common-note-form js-requires-input js-quick-submit' },
-           data: { markdown_version: @merge_request.cached_markdown_version } do |f|
+           html: { class: 'merge-request-form common-note-form js-requires-input js-quick-submit' } do |f|
   = render 'shared/issuable/form', f: f, issuable: @merge_request, presenter: @mr_presenter
diff --git a/app/views/projects/milestones/_form.html.haml b/app/views/projects/milestones/_form.html.haml
index 19f5bba75c4..5cc6b5a173b 100644
--- a/app/views/projects/milestones/_form.html.haml
+++ b/app/views/projects/milestones/_form.html.haml
@@ -1,6 +1,5 @@
 = form_for [@project.namespace.becomes(Namespace), @project, @milestone],
-           html: { class: 'milestone-form common-note-form js-quick-submit js-requires-input' },
-           data: { markdown_version: @milestone.cached_markdown_version } do |f|
+           html: { class: 'milestone-form common-note-form js-quick-submit js-requires-input' } do |f|
   = form_errors(@milestone)
   .row
     .col-md-6
diff --git a/app/views/projects/tags/releases/edit.html.haml b/app/views/projects/tags/releases/edit.html.haml
index 52c6c7ec424..e4efeed04f0 100644
--- a/app/views/projects/tags/releases/edit.html.haml
+++ b/app/views/projects/tags/releases/edit.html.haml
@@ -12,8 +12,7 @@
 
 
   = form_for(@release, method: :put, url: project_tag_release_path(@project, @tag.name),
-             html: { class: 'common-note-form release-form js-quick-submit' },
-             data: { markdown_version: @release.cached_markdown_version }) do |f|
+             html: { class: 'common-note-form release-form js-quick-submit' }) do |f|
     = render layout: 'projects/md_preview', locals: { url: preview_markdown_path(@project), referenced_users: true } do
       = render 'projects/zen', f: f, attr: :description, classes: 'note-textarea', placeholder: "Write your release notes or drag files here…"
       = render 'shared/notes/hints'
diff --git a/app/views/projects/wikis/_form.html.haml b/app/views/projects/wikis/_form.html.haml
index d1556dbd077..5bb69563b51 100644
--- a/app/views/projects/wikis/_form.html.haml
+++ b/app/views/projects/wikis/_form.html.haml
@@ -1,13 +1,9 @@
 - commit_message = @page.persisted? ? s_("WikiPageEdit|Update %{page_title}") : s_("WikiPageCreate|Create %{page_title}")
 - commit_message = commit_message % { page_title: @page.title }
-- if params[:legacy_render] || !commonmark_for_repositories_enabled?
-  - markdown_version = CacheMarkdownField::CACHE_REDCARPET_VERSION
-- else
-  - markdown_version = 0
 
 = form_for [@project.namespace.becomes(Namespace), @project, @page], method: @page.persisted? ? :put : :post,
            html: { class: 'wiki-form common-note-form prepend-top-default js-quick-submit' },
-           data: { markdown_version: markdown_version, uploads_path: uploads_path } do |f|
+           data: { uploads_path: uploads_path } do |f|
   = form_errors(@page)
 
   - if @page.persisted?
diff --git a/app/views/projects/wikis/_sidebar.html.haml b/app/views/projects/wikis/_sidebar.html.haml
index 02c5a6ea55c..28353927135 100644
--- a/app/views/projects/wikis/_sidebar.html.haml
+++ b/app/views/projects/wikis/_sidebar.html.haml
@@ -12,7 +12,7 @@
     .blocks-container
       .block.block-first
         - if @sidebar_page
-          = render_wiki_content(@sidebar_page, legacy_render_context(params))
+          = render_wiki_content(@sidebar_page)
         - else
           %ul.wiki-pages
             = render @sidebar_wiki_entries, context: 'sidebar'
diff --git a/app/views/projects/wikis/show.html.haml b/app/views/projects/wikis/show.html.haml
index 8b348bb4e4f..8e1c054b50c 100644
--- a/app/views/projects/wikis/show.html.haml
+++ b/app/views/projects/wikis/show.html.haml
@@ -27,6 +27,6 @@
 
 .prepend-top-default.append-bottom-default
   .wiki.md{ class: ('use-csslab' if Feature.enabled?(:csslab)) }
-    = render_wiki_content(@page, legacy_render_context(params))
+    = render_wiki_content(@page)
 
 = render 'sidebar'
diff --git a/app/views/search/results/_snippet_blob.html.haml b/app/views/search/results/_snippet_blob.html.haml
index e0130f9a4b5..a60a4501557 100644
--- a/app/views/search/results/_snippet_blob.html.haml
+++ b/app/views/search/results/_snippet_blob.html.haml
@@ -21,7 +21,7 @@
       .file-content.wiki
         - snippet_chunks.each do |chunk|
           - unless chunk[:data].empty?
-            = markup(snippet.file_name, chunk[:data], legacy_render_context(params))
+            = markup(snippet.file_name, chunk[:data])
           - else
             .file-content.code
               .nothing-here-block= _("Empty file")
diff --git a/app/views/shared/notes/_note.html.haml b/app/views/shared/notes/_note.html.haml
index cb5c64fb91d..41d6ae79c81 100644
--- a/app/views/shared/notes/_note.html.haml
+++ b/app/views/shared/notes/_note.html.haml
@@ -54,7 +54,7 @@
         .note-text.md
           = markdown_field(note, :note)
         = edited_time_ago_with_tooltip(note, placement: 'bottom', html_class: 'note_edited_ago')
-        .original-note-content.hidden{ data: { post_url: note_url(note), target_id: note.noteable.id, target_type: note.noteable.class.name.underscore, markdown_version: note.cached_markdown_version } }
+        .original-note-content.hidden{ data: { post_url: note_url(note), target_id: note.noteable.id, target_type: note.noteable.class.name.underscore } }
           #{note.note}
         - if note_editable
           = render 'shared/notes/edit', note: note
diff --git a/app/views/shared/snippets/_form.html.haml b/app/views/shared/snippets/_form.html.haml
index cf9c3055499..3007da0c189 100644
--- a/app/views/shared/snippets/_form.html.haml
+++ b/app/views/shared/snippets/_form.html.haml
@@ -3,8 +3,7 @@
 
 .snippet-form-holder
   = form_for @snippet, url: url,
-             html: { class: "snippet-form js-requires-input js-quick-submit common-note-form" },
-             data: { markdown_version: @snippet.cached_markdown_version } do |f|
+             html: { class: "snippet-form js-requires-input js-quick-submit common-note-form" } do |f|
     = form_errors(@snippet)
 
     .form-group.row
diff --git a/changelogs/unreleased/jprovazn-remove-redcarpet.yml b/changelogs/unreleased/jprovazn-remove-redcarpet.yml
new file mode 100644
index 00000000000..4e12de2d19b
--- /dev/null
+++ b/changelogs/unreleased/jprovazn-remove-redcarpet.yml
@@ -0,0 +1,5 @@
+---
+title: Removed deprecated Redcarpet markdown engine.
+merge_request:
+author:
+type: removed
diff --git a/doc/user/markdown.md b/doc/user/markdown.md
index f2448f240ca..9a01625f3ff 100644
--- a/doc/user/markdown.md
+++ b/doc/user/markdown.md
@@ -31,8 +31,10 @@ dependency to do so. Please see the [`github-markup` gem readme](https://github.
 > As of 11.1, GitLab uses the [CommonMark Ruby Library][commonmarker] for Markdown
 processing of all new issues, merge requests, comments, and other Markdown content
 in the GitLab system. As of 11.3, wiki pages and Markdown files (`.md`) in the
-repositories are also processed with CommonMark. Older content in issues/comments
-are still processed using the [Redcarpet Ruby library][redcarpet].
+repositories are also processed with CommonMark. As of 11.8, the [Redcarpet
+Ruby library][redcarpet] has been removed and all issues/comments, including
+those from pre-11.1, are now processed using [CommonMark Ruby
+Library][commonmarker].
 >
 > The documentation website had its [markdown engine migrated from Redcarpet to Kramdown](https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/108)
 in October 2018.
@@ -41,11 +43,11 @@ in October 2018.
 
 ### Transitioning to CommonMark
 
-You may have Markdown documents in your repository that were written using some
-of the nuances of RedCarpet's version of Markdown. Since CommonMark uses a
-slightly stricter syntax, these documents may now display a little strangely
-since we've transitioned to CommonMark. Numbered lists with nested lists in
-particular can be displayed incorrectly.
+You may have older issues/merge requests or Markdown documents in your
+repository that were written using some of the nuances of RedCarpet's version
+of Markdown. Since CommonMark uses a slightly stricter syntax, these documents
+may now display a little strangely since we've transitioned to CommonMark.
+Numbered lists with nested lists in particular can be displayed incorrectly.
 
 It is usually quite easy to fix.  In the case of a nested list such as this:
 
@@ -65,11 +67,6 @@ simply add a space to each nested item:
 
 In the documentation below, we try to highlight some of the differences.
 
-If you have a need to view a document using RedCarpet, you can add the token
-`legacy_render=1` to the end of the url, like this:
-
-https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/user/markdown.md?legacy_render=1
-
 If you have a large volume of Markdown files, it can be tedious to determine
 if they will be displayed correctly or not. You can use the
 [diff_redcarpet_cmark](https://gitlab.com/digitalmoksha/diff_redcarpet_cmark)
@@ -677,7 +674,7 @@ Becomes:
 + Or pluses
 
 If a list item contains multiple paragraphs,
-each subsequent paragraph should be indented to the same level as the start of the list item text (_Redcarpet: paragraph should be indented with four spaces._)
+each subsequent paragraph should be indented to the same level as the start of the list item text
 
 Example:
 
@@ -841,7 +838,7 @@ These details <em>will</em> remain <strong>hidden</strong> until expanded.
 </details>
 </p>
 
-**Note:** Markdown inside these tags is supported, as long as you have a blank line after the `</summary>` tag and before the `</details>` tag, as shown in the example.  _Redcarpet does not support Markdown inside these tags.  You can work around this by using HTML, for example you can use `<pre><code>` tags instead of [code fences](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/user/markdown.md#code-and-syntax-highlighting)._
+**Note:** Markdown inside these tags is supported, as long as you have a blank line after the `</summary>` tag and before the `</details>` tag, as shown in the example.
 
 ```html
 <details>
diff --git a/lib/banzai/filter/markdown_engines/redcarpet.rb b/lib/banzai/filter/markdown_engines/redcarpet.rb
deleted file mode 100644
index 5b3f75096b1..00000000000
--- a/lib/banzai/filter/markdown_engines/redcarpet.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-# frozen_string_literal: true
-
-# `Redcarpet` markdown engine for GitLab's Banzai markdown filter.
-# This module is used in Banzai::Filter::MarkdownFilter.
-# Used gem is `redcarpet` which is a ruby library for markdown processing.
-# Homepage: https://github.com/vmg/redcarpet
-
-module Banzai
-  module Filter
-    module MarkdownEngines
-      class Redcarpet
-        OPTIONS = {
-          fenced_code_blocks:  true,
-          footnotes:           true,
-          lax_spacing:         true,
-          no_intra_emphasis:   true,
-          space_after_headers: true,
-          strikethrough:       true,
-          superscript:         true,
-          tables:              true
-        }.freeze
-
-        def initialize(context = nil)
-          html_renderer = Banzai::Renderer::Redcarpet::HTML.new
-          @renderer = ::Redcarpet::Markdown.new(html_renderer, OPTIONS)
-        end
-
-        def render(text)
-          @renderer.render(text)
-        end
-      end
-    end
-  end
-end
diff --git a/lib/banzai/filter/spaced_link_filter.rb b/lib/banzai/filter/spaced_link_filter.rb
index 00dbf2d3130..50bf823929c 100644
--- a/lib/banzai/filter/spaced_link_filter.rb
+++ b/lib/banzai/filter/spaced_link_filter.rb
@@ -45,8 +45,6 @@ module Banzai
       ]).freeze
 
       def call
-        return doc if context[:markdown_engine] == :redcarpet
-
         doc.xpath(TEXT_QUERY).each do |node|
           content = node.to_html
 
diff --git a/lib/banzai/filter/syntax_highlight_filter.rb b/lib/banzai/filter/syntax_highlight_filter.rb
index bcf77861f10..9ffde52b5f2 100644
--- a/lib/banzai/filter/syntax_highlight_filter.rb
+++ b/lib/banzai/filter/syntax_highlight_filter.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'rouge/plugins/common_mark'
-require 'rouge/plugins/redcarpet'
 
 # Generated HTML is transformed back to GFM by app/assets/javascripts/behaviors/markdown/nodes/code_block.js
 module Banzai
diff --git a/lib/banzai/renderer/redcarpet/html.rb b/lib/banzai/renderer/redcarpet/html.rb
deleted file mode 100644
index 84931fdc784..00000000000
--- a/lib/banzai/renderer/redcarpet/html.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module Banzai
-  module Renderer
-    module Redcarpet
-      class HTML < ::Redcarpet::Render::HTML
-        def block_code(code, lang)
-          lang_attr = lang ? %Q{ lang="#{lang}"} : ''
-
-          "\n<pre>" \
-            "<code#{lang_attr}>#{ERB::Util.html_escape(code)}</code>" \
-          "</pre>"
-        end
-      end
-    end
-  end
-end
diff --git a/spec/features/markdown/markdown_spec.rb b/spec/features/markdown/markdown_spec.rb
index 3b37ede8579..8815643ca96 100644
--- a/spec/features/markdown/markdown_spec.rb
+++ b/spec/features/markdown/markdown_spec.rb
@@ -13,7 +13,7 @@ require 'erb'
 #
 #   Raw Markdown
 #   -> `markdown` helper
-#     -> Redcarpet::Render::GitlabHTML converts Markdown to HTML
+#     -> CommonMark::Render::GitlabHTML converts Markdown to HTML
 #       -> Post-process HTML
 #         -> `gfm` helper
 #           -> HTML::Pipeline
@@ -324,31 +324,6 @@ describe 'GitLab Markdown', :aggregate_failures do
     end
   end
 
-  context 'Redcarpet documents' do
-    before do
-      allow_any_instance_of(Banzai::Filter::MarkdownFilter).to receive(:engine).and_return('Redcarpet')
-      @html = markdown(@feat.raw_markdown)
-    end
-
-    it 'processes certain elements differently' do
-      aggregate_failures 'parses superscript' do
-        expect(doc).to have_selector('sup', count: 3)
-      end
-
-      aggregate_failures 'permits style attribute in th elements' do
-        expect(doc.at_css('th:contains("Header")')['style']).to eq 'text-align: center'
-        expect(doc.at_css('th:contains("Row")')['style']).to eq 'text-align: right'
-        expect(doc.at_css('th:contains("Example")')['style']).to eq 'text-align: left'
-      end
-
-      aggregate_failures 'permits style attribute in td elements' do
-        expect(doc.at_css('td:contains("Foo")')['style']).to eq 'text-align: center'
-        expect(doc.at_css('td:contains("Bar")')['style']).to eq 'text-align: right'
-        expect(doc.at_css('td:contains("Baz")')['style']).to eq 'text-align: left'
-      end
-    end
-  end
-
   # Fake a `current_user` helper
   def current_user
     @feat.user
diff --git a/spec/features/projects/blobs/blob_show_spec.rb b/spec/features/projects/blobs/blob_show_spec.rb
index e2f9e7e9cc5..3edcc7ac2cd 100644
--- a/spec/features/projects/blobs/blob_show_spec.rb
+++ b/spec/features/projects/blobs/blob_show_spec.rb
@@ -5,8 +5,8 @@ describe 'File blob', :js do
 
   let(:project) { create(:project, :public, :repository) }
 
-  def visit_blob(path, anchor: nil, ref: 'master', legacy_render: nil)
-    visit project_blob_path(project, File.join(ref, path), anchor: anchor, legacy_render: legacy_render)
+  def visit_blob(path, anchor: nil, ref: 'master')
+    visit project_blob_path(project, File.join(ref, path), anchor: anchor)
 
     wait_for_requests
   end
@@ -171,21 +171,6 @@ describe 'File blob', :js do
         end
       end
     end
-
-    context 'when rendering legacy markdown' do
-      before do
-        visit_blob('files/commonmark/file.md', legacy_render: 1)
-
-        wait_for_requests
-      end
-
-      it 'renders using RedCarpet' do
-        aggregate_failures do
-          expect(page).to have_content("sublist")
-          expect(page).to have_xpath("//ol//li//ul")
-        end
-      end
-    end
   end
 
   context 'Markdown file (stored in LFS)' do
diff --git a/spec/features/projects/blobs/edit_spec.rb b/spec/features/projects/blobs/edit_spec.rb
index d5b20605860..6e6c299ee2e 100644
--- a/spec/features/projects/blobs/edit_spec.rb
+++ b/spec/features/projects/blobs/edit_spec.rb
@@ -81,17 +81,6 @@ describe 'Editing file blob', :js do
         expect(page).to have_content("sublist")
         expect(page).not_to have_xpath("//ol//li//ul")
       end
-
-      it 'renders content with RedCarpet when legacy_render is set' do
-        visit project_edit_blob_path(project, tree_join(branch, readme_file_path), legacy_render: 1)
-        fill_editor(content: "1. one\\n  - sublist\\n")
-        click_link 'Preview'
-        wait_for_requests
-
-        # the above generates a sublist list in RedCarpet
-        expect(page).to have_content("sublist")
-        expect(page).to have_xpath("//ol//li//ul")
-      end
     end
   end
 
diff --git a/spec/features/projects/wiki/markdown_preview_spec.rb b/spec/features/projects/wiki/markdown_preview_spec.rb
index f505023d1d0..3b469fee867 100644
--- a/spec/features/projects/wiki/markdown_preview_spec.rb
+++ b/spec/features/projects/wiki/markdown_preview_spec.rb
@@ -175,20 +175,6 @@ describe 'Projects > Wiki > User previews markdown changes', :js do
         expect(page).to have_content("sublist")
         expect(page).not_to have_xpath("//ol//li//ul")
       end
-
-      it 'renders content with RedCarpet when legacy_render is set' do
-        wiki_page = create(:wiki_page,
-                           wiki: project.wiki,
-                           attrs: { title: 'home', content: "Empty content" })
-        visit(project_wiki_edit_path(project, wiki_page, legacy_render: 1))
-
-        fill_in :wiki_content, with: "1. one\n  - sublist\n"
-        click_on "Preview"
-
-        # the above generates a sublist list in RedCarpet
-        expect(page).to have_content("sublist")
-        expect(page).to have_xpath("//ol//li//ul")
-      end
     end
   end
 
diff --git a/spec/features/snippets/show_spec.rb b/spec/features/snippets/show_spec.rb
index 367a479f62a..eb974c7c7fd 100644
--- a/spec/features/snippets/show_spec.rb
+++ b/spec/features/snippets/show_spec.rb
@@ -80,19 +80,6 @@ describe 'Snippet', :js do
           end
         end
 
-        context 'when rendering legacy markdown' do
-          before do
-            visit snippet_path(snippet, legacy_render: 1)
-
-            wait_for_requests
-          end
-
-          it 'renders using RedCarpet' do
-            expect(page).to have_content("sublist")
-            expect(page).to have_xpath("//ol//li//ul")
-          end
-        end
-
         context 'with cached CommonMark html' do
           let(:snippet) { create(:personal_snippet, :public, file_name: file_name, content: content, cached_markdown_version: CacheMarkdownField::CACHE_COMMONMARK_VERSION) }
 
@@ -100,14 +87,6 @@ describe 'Snippet', :js do
             expect(page).not_to have_xpath("//ol//li//ul")
           end
         end
-
-        context 'with cached Redcarpet html' do
-          let(:snippet) { create(:personal_snippet, :public, file_name: file_name, content: content, cached_markdown_version: CacheMarkdownField::CACHE_REDCARPET_VERSION) }
-
-          it 'renders correctly' do
-            expect(page).to have_xpath("//ol//li//ul")
-          end
-        end
       end
 
       context 'switching to the simple viewer' do
diff --git a/spec/features/task_lists_spec.rb b/spec/features/task_lists_spec.rb
index b549f2b5c62..6fe840dccf6 100644
--- a/spec/features/task_lists_spec.rb
+++ b/spec/features/task_lists_spec.rb
@@ -36,19 +36,6 @@ describe 'Task Lists' do
     MARKDOWN
   end
 
-  let(:nested_tasks_markdown_redcarpet) do
-    <<-EOT.strip_heredoc
-    - [ ] Task a
-      - [x] Task a.1
-      - [ ] Task a.2
-    - [ ] Task b
-
-    1. [ ] Task 1
-      1. [ ] Task 1.1
-      1. [x] Task 1.2
-    EOT
-  end
-
   let(:nested_tasks_markdown) do
     <<-EOT.strip_heredoc
     - [ ] Task a
@@ -153,61 +140,6 @@ describe 'Task Lists' do
         expect(page).to have_content("1 of 1 task completed")
       end
     end
-
-    shared_examples 'shared nested tasks' do
-      before do
-        allow(Banzai::Filter::MarkdownFilter).to receive(:engine).and_return('Redcarpet')
-        visit_issue(project, issue)
-      end
-      it 'renders' do
-        expect(page).to have_selector('ul.task-list',      count: 2)
-        expect(page).to have_selector('li.task-list-item', count: 7)
-        expect(page).to have_selector('ul input[checked]', count: 1)
-        expect(page).to have_selector('ol input[checked]', count: 1)
-      end
-
-      it 'solves tasks' do
-        expect(page).to have_content("2 of 7 tasks completed")
-
-        page.find('li.task-list-item', text: 'Task b').find('input').click
-        wait_for_requests
-        page.find('li.task-list-item ul li.task-list-item', text: 'Task a.2').find('input').click
-        wait_for_requests
-        page.find('li.task-list-item ol li.task-list-item', text: 'Task 1.1').find('input').click
-        wait_for_requests
-
-        expect(page).to have_content("5 of 7 tasks completed")
-
-        visit_issue(project, issue) # reload to see new system notes
-
-        expect(page).to have_content('marked the task Task b as complete')
-        expect(page).to have_content('marked the task Task a.2 as complete')
-        expect(page).to have_content('marked the task Task 1.1 as complete')
-      end
-    end
-
-    describe 'nested tasks', :js do
-      let(:cache_version) { CacheMarkdownField::CACHE_COMMONMARK_VERSION }
-      let!(:issue) do
-        create(:issue, description: nested_tasks_markdown, author: user, project: project,
-                       cached_markdown_version: cache_version)
-      end
-
-      before do
-        visit_issue(project, issue)
-      end
-
-      context 'with Redcarpet' do
-        let(:cache_version) { CacheMarkdownField::CACHE_REDCARPET_VERSION }
-        let(:nested_tasks_markdown) { nested_tasks_markdown_redcarpet }
-
-        it_behaves_like 'shared nested tasks'
-      end
-
-      context 'with CommonMark' do
-        it_behaves_like 'shared nested tasks'
-      end
-    end
   end
 
   describe 'for Notes' do
diff --git a/spec/fixtures/markdown.md.erb b/spec/fixtures/markdown.md.erb
index e5d01c3bd03..bbeacf1707b 100644
--- a/spec/fixtures/markdown.md.erb
+++ b/spec/fixtures/markdown.md.erb
@@ -6,7 +6,7 @@ started.
 
 ## Markdown
 
-GitLab uses [Redcarpet](http://git.io/ld_NVQ) to parse all Markdown into
+GitLab uses [Commonmark](https://git.io/fhDag) to parse all Markdown into
 HTML.
 
 It has some special features. Let's try 'em out!
diff --git a/spec/helpers/issuables_helper_spec.rb b/spec/helpers/issuables_helper_spec.rb
index af319e5ebfe..8b82dea2524 100644
--- a/spec/helpers/issuables_helper_spec.rb
+++ b/spec/helpers/issuables_helper_spec.rb
@@ -188,7 +188,6 @@ describe IssuablesHelper do
         issuableRef: "##{issue.iid}",
         markdownPreviewPath: "/#{@project.full_path}/preview_markdown",
         markdownDocsPath: '/help/user/markdown',
-        markdownVersion: CacheMarkdownField::CACHE_COMMONMARK_VERSION,
         issuableTemplates: [],
         lockVersion: issue.lock_version,
         projectPath: @project.path,
diff --git a/spec/helpers/markup_helper_spec.rb b/spec/helpers/markup_helper_spec.rb
index a0c0af94fa5..c3956ba08fd 100644
--- a/spec/helpers/markup_helper_spec.rb
+++ b/spec/helpers/markup_helper_spec.rb
@@ -212,17 +212,6 @@ describe MarkupHelper do
       helper.render_wiki_content(@wiki)
     end
 
-    it 'uses Wiki pipeline for markdown files with RedCarpet if feature disabled' do
-      stub_feature_flags(commonmark_for_repositories: false)
-      allow(@wiki).to receive(:format).and_return(:markdown)
-
-      expect(helper).to receive(:markdown_unsafe).with('wiki content',
-        pipeline: :wiki, project: project, project_wiki: @wiki, page_slug: "nested/page",
-        issuable_state_filter_enabled: true, markdown_engine: :redcarpet)
-
-      helper.render_wiki_content(@wiki)
-    end
-
     it "uses Asciidoctor for asciidoc files" do
       allow(@wiki).to receive(:format).and_return(:asciidoc)
 
@@ -273,16 +262,6 @@ describe MarkupHelper do
     it 'defaults to CommonMark' do
       expect(helper.markup('foo.md', 'x^2')).to include('x^2')
     end
-
-    it 'honors markdown_engine for RedCarpet' do
-      expect(helper.markup('foo.md', 'x^2', { markdown_engine: :redcarpet })).to include('x<sup>2</sup>')
-    end
-
-    it 'uses RedCarpet if feature disabled' do
-      stub_feature_flags(commonmark_for_repositories: false)
-
-      expect(helper.markup('foo.md', 'x^2', { markdown_engine: :redcarpet })).to include('x<sup>2</sup>')
-    end
   end
 
   describe '#first_line_in_markdown' do
diff --git a/spec/helpers/projects_helper_spec.rb b/spec/helpers/projects_helper_spec.rb
index 10f61731206..098ccc1b5be 100644
--- a/spec/helpers/projects_helper_spec.rb
+++ b/spec/helpers/projects_helper_spec.rb
@@ -540,18 +540,6 @@ describe ProjectsHelper do
     end
   end
 
-  describe '#legacy_render_context' do
-    it 'returns the redcarpet engine' do
-      params = { legacy_render: '1' }
-
-      expect(helper.legacy_render_context(params)).to include(markdown_engine: :redcarpet)
-    end
-
-    it 'returns nothing' do
-      expect(helper.legacy_render_context({})).to be_empty
-    end
-  end
-
   describe '#explore_projects_tab?' do
     subject { helper.explore_projects_tab? }
 
diff --git a/spec/lib/banzai/filter/markdown_filter_spec.rb b/spec/lib/banzai/filter/markdown_filter_spec.rb
index 4c4e821deab..83fcda29680 100644
--- a/spec/lib/banzai/filter/markdown_filter_spec.rb
+++ b/spec/lib/banzai/filter/markdown_filter_spec.rb
@@ -10,12 +10,6 @@ describe Banzai::Filter::MarkdownFilter do
       filter('test')
     end
 
-    it 'uses Redcarpet' do
-      expect_any_instance_of(Banzai::Filter::MarkdownEngines::Redcarpet).to receive(:render).and_return('test')
-
-      filter('test', { markdown_engine: :redcarpet })
-    end
-
     it 'uses CommonMark' do
       expect_any_instance_of(Banzai::Filter::MarkdownEngines::CommonMark).to receive(:render).and_return('test')
 
@@ -47,24 +41,6 @@ describe Banzai::Filter::MarkdownFilter do
         expect(result).to start_with('<pre><code lang="日">')
       end
     end
-
-    context 'using Redcarpet' do
-      before do
-        stub_const('Banzai::Filter::MarkdownFilter::DEFAULT_ENGINE', :redcarpet)
-      end
-
-      it 'adds language to lang attribute when specified' do
-        result = filter("```html\nsome code\n```")
-
-        expect(result).to start_with("\n<pre><code lang=\"html\">")
-      end
-
-      it 'does not add language to lang attribute when not specified' do
-        result = filter("```\nsome code\n```")
-
-        expect(result).to start_with("\n<pre><code>")
-      end
-    end
   end
 
   describe 'source line position' do
@@ -85,18 +61,6 @@ describe Banzai::Filter::MarkdownFilter do
         expect(result).to eq '<p>test</p>'
       end
     end
-
-    context 'using Redcarpet' do
-      before do
-        stub_const('Banzai::Filter::MarkdownFilter::DEFAULT_ENGINE', :redcarpet)
-      end
-
-      it 'does not support data-sourcepos' do
-        result = filter('test')
-
-        expect(result).to eq '<p>test</p>'
-      end
-    end
   end
 
   describe 'footnotes in tables' do
diff --git a/spec/lib/banzai/filter/spaced_link_filter_spec.rb b/spec/lib/banzai/filter/spaced_link_filter_spec.rb
index 1ad7f3ff567..76d7644d76c 100644
--- a/spec/lib/banzai/filter/spaced_link_filter_spec.rb
+++ b/spec/lib/banzai/filter/spaced_link_filter_spec.rb
@@ -26,11 +26,6 @@ describe Banzai::Filter::SpacedLinkFilter do
       expect(doc.at_css('p')).to be_nil
     end
 
-    it 'does nothing when markdown_engine is redcarpet' do
-      exp = act = link
-      expect(filter(act, markdown_engine: :redcarpet).to_html).to eq exp
-    end
-
     it 'does nothing with empty text' do
       link = '[](page slug)'
       doc  = filter("See #{link}")
diff --git a/spec/models/concerns/cache_markdown_field_spec.rb b/spec/models/concerns/cache_markdown_field_spec.rb
index 925e2ab0955..29197ef372e 100644
--- a/spec/models/concerns/cache_markdown_field_spec.rb
+++ b/spec/models/concerns/cache_markdown_field_spec.rb
@@ -73,6 +73,7 @@ describe CacheMarkdownField do
   let(:updated_html)     { '<p dir="auto"><code>Bar</code></p>' }
 
   let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: CacheMarkdownField::CACHE_COMMONMARK_VERSION) }
+  let(:cache_version) { CacheMarkdownField::CACHE_COMMONMARK_VERSION }
 
   before do
     stub_commonmark_sourcepos_disabled
@@ -97,20 +98,15 @@ describe CacheMarkdownField do
   end
 
   context 'a changed markdown field' do
-    shared_examples 'with cache version' do |cache_version|
-      let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
+    let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
 
-      before do
-        thing.foo = updated_markdown
-        thing.save
-      end
-
-      it { expect(thing.foo_html).to eq(updated_html) }
-      it { expect(thing.cached_markdown_version).to eq(cache_version) }
+    before do
+      thing.foo = updated_markdown
+      thing.save
     end
 
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_REDCARPET_VERSION
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_COMMONMARK_VERSION
+    it { expect(thing.foo_html).to eq(updated_html) }
+    it { expect(thing.cached_markdown_version).to eq(cache_version) }
   end
 
   context 'when a markdown field is set repeatedly to an empty string' do
@@ -143,22 +139,17 @@ describe CacheMarkdownField do
   end
 
   context 'a non-markdown field changed' do
-    shared_examples 'with cache version' do |cache_version|
-      let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
-
-      before do
-        thing.bar = 'OK'
-        thing.save
-      end
+    let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
 
-      it { expect(thing.bar).to eq('OK') }
-      it { expect(thing.foo).to eq(markdown) }
-      it { expect(thing.foo_html).to eq(html) }
-      it { expect(thing.cached_markdown_version).to eq(cache_version) }
+    before do
+      thing.bar = 'OK'
+      thing.save
     end
 
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_REDCARPET_VERSION
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_COMMONMARK_VERSION
+    it { expect(thing.bar).to eq('OK') }
+    it { expect(thing.foo).to eq(markdown) }
+    it { expect(thing.foo_html).to eq(html) }
+    it { expect(thing.cached_markdown_version).to eq(cache_version) }
   end
 
   context 'version is out of date' do
@@ -173,73 +164,63 @@ describe CacheMarkdownField do
   end
 
   describe '#cached_html_up_to_date?' do
-    shared_examples 'with cache version' do |cache_version|
-      let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
+    let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
 
-      subject { thing.cached_html_up_to_date?(:foo) }
+    subject { thing.cached_html_up_to_date?(:foo) }
 
-      it 'returns false when the version is absent' do
-        thing.cached_markdown_version = nil
+    it 'returns false when the version is absent' do
+      thing.cached_markdown_version = nil
 
-        is_expected.to be_falsy
-      end
+      is_expected.to be_falsy
+    end
 
-      it 'returns false when the version is too early' do
-        thing.cached_markdown_version -= 1
+    it 'returns false when the version is too early' do
+      thing.cached_markdown_version -= 1
 
-        is_expected.to be_falsy
-      end
+      is_expected.to be_falsy
+    end
 
-      it 'returns false when the version is too late' do
-        thing.cached_markdown_version += 1
+    it 'returns false when the version is too late' do
+      thing.cached_markdown_version += 1
 
-        is_expected.to be_falsy
-      end
+      is_expected.to be_falsy
+    end
 
-      it 'returns true when the version is just right' do
-        thing.cached_markdown_version = cache_version
+    it 'returns true when the version is just right' do
+      thing.cached_markdown_version = cache_version
 
-        is_expected.to be_truthy
-      end
+      is_expected.to be_truthy
+    end
 
-      it 'returns false if markdown has been changed but html has not' do
-        thing.foo = updated_html
+    it 'returns false if markdown has been changed but html has not' do
+      thing.foo = updated_html
 
-        is_expected.to be_falsy
-      end
+      is_expected.to be_falsy
+    end
 
-      it 'returns true if markdown has not been changed but html has' do
-        thing.foo_html = updated_html
+    it 'returns true if markdown has not been changed but html has' do
+      thing.foo_html = updated_html
 
-        is_expected.to be_truthy
-      end
+      is_expected.to be_truthy
+    end
 
-      it 'returns true if markdown and html have both been changed' do
-        thing.foo = updated_markdown
-        thing.foo_html = updated_html
+    it 'returns true if markdown and html have both been changed' do
+      thing.foo = updated_markdown
+      thing.foo_html = updated_html
 
-        is_expected.to be_truthy
-      end
+      is_expected.to be_truthy
+    end
 
-      it 'returns false if the markdown field is set but the html is not' do
-        thing.foo_html = nil
+    it 'returns false if the markdown field is set but the html is not' do
+      thing.foo_html = nil
 
-        is_expected.to be_falsy
-      end
+      is_expected.to be_falsy
     end
-
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_REDCARPET_VERSION
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_COMMONMARK_VERSION
   end
 
   describe '#latest_cached_markdown_version' do
     subject { thing.latest_cached_markdown_version }
 
-    it 'returns redcarpet version' do
-      thing.cached_markdown_version = CacheMarkdownField::CACHE_COMMONMARK_VERSION_START - 1
-      is_expected.to eq(CacheMarkdownField::CACHE_REDCARPET_VERSION)
-    end
-
     it 'returns commonmark version' do
       thing.cached_markdown_version = CacheMarkdownField::CACHE_COMMONMARK_VERSION_START + 1
       is_expected.to eq(CacheMarkdownField::CACHE_COMMONMARK_VERSION)
@@ -251,30 +232,6 @@ describe CacheMarkdownField do
     end
   end
 
-  describe '#legacy_markdown?' do
-    subject { thing.legacy_markdown? }
-
-    it 'returns true for redcarpet versions' do
-      thing.cached_markdown_version = CacheMarkdownField::CACHE_COMMONMARK_VERSION_START - 1
-      is_expected.to be_truthy
-    end
-
-    it 'returns false for commonmark versions' do
-      thing.cached_markdown_version = CacheMarkdownField::CACHE_COMMONMARK_VERSION_START
-      is_expected.to be_falsey
-    end
-
-    it 'returns false if nil' do
-      thing.cached_markdown_version = nil
-      is_expected.to be_falsey
-    end
-
-    it 'returns false if 0' do
-      thing.cached_markdown_version = 0
-      is_expected.to be_falsey
-    end
-  end
-
   describe '#refresh_markdown_cache' do
     before do
       thing.foo = updated_markdown
@@ -303,39 +260,34 @@ describe CacheMarkdownField do
   end
 
   describe '#refresh_markdown_cache!' do
-    shared_examples 'with cache version' do |cache_version|
-      let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
+    let(:thing) { ThingWithMarkdownFields.new(foo: markdown, foo_html: html, cached_markdown_version: cache_version) }
 
-      before do
-        thing.foo = updated_markdown
-      end
+    before do
+      thing.foo = updated_markdown
+    end
 
-      it 'fills all html fields' do
-        thing.refresh_markdown_cache!
+    it 'fills all html fields' do
+      thing.refresh_markdown_cache!
 
-        expect(thing.foo_html).to eq(updated_html)
-        expect(thing.foo_html_changed?).to be_truthy
-        expect(thing.baz_html_changed?).to be_truthy
-      end
+      expect(thing.foo_html).to eq(updated_html)
+      expect(thing.foo_html_changed?).to be_truthy
+      expect(thing.baz_html_changed?).to be_truthy
+    end
 
-      it 'skips saving if not persisted' do
-        expect(thing).to receive(:persisted?).and_return(false)
-        expect(thing).not_to receive(:update_columns)
+    it 'skips saving if not persisted' do
+      expect(thing).to receive(:persisted?).and_return(false)
+      expect(thing).not_to receive(:update_columns)
 
-        thing.refresh_markdown_cache!
-      end
+      thing.refresh_markdown_cache!
+    end
 
-      it 'saves the changes using #update_columns' do
-        expect(thing).to receive(:persisted?).and_return(true)
-        expect(thing).to receive(:update_columns)
-          .with("foo_html" => updated_html, "baz_html" => "", "cached_markdown_version" => cache_version)
+    it 'saves the changes using #update_columns' do
+      expect(thing).to receive(:persisted?).and_return(true)
+      expect(thing).to receive(:update_columns)
+        .with("foo_html" => updated_html, "baz_html" => "", "cached_markdown_version" => cache_version)
 
-        thing.refresh_markdown_cache!
-      end
+      thing.refresh_markdown_cache!
     end
-
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_REDCARPET_VERSION
-    it_behaves_like 'with cache version', CacheMarkdownField::CACHE_COMMONMARK_VERSION
   end
 
   describe '#banzai_render_context' do
@@ -408,20 +360,4 @@ describe CacheMarkdownField do
       end
     end
   end
-
-  describe CacheMarkdownField::MarkdownEngine do
-    subject { lambda { |version| CacheMarkdownField::MarkdownEngine.from_version(version) } }
-
-    it 'returns :common_mark as a default' do
-      expect(subject.call(nil)).to eq :common_mark
-    end
-
-    it 'returns :common_mark' do
-      expect(subject.call(CacheMarkdownField::CACHE_COMMONMARK_VERSION)).to eq :common_mark
-    end
-
-    it 'returns :redcarpet' do
-      expect(subject.call(CacheMarkdownField::CACHE_REDCARPET_VERSION)).to eq :redcarpet
-    end
-  end
 end
diff --git a/spec/services/preview_markdown_service_spec.rb b/spec/services/preview_markdown_service_spec.rb
index 458cb8f1f31..85515d548a7 100644
--- a/spec/services/preview_markdown_service_spec.rb
+++ b/spec/services/preview_markdown_service_spec.rb
@@ -114,23 +114,4 @@ describe PreviewMarkdownService do
       expect(result[:commands]).to eq 'Tags this commit to v1.2.3 with "Stable release".'
     end
   end
-
-  it 'sets correct markdown engine' do
-    service = described_class.new(project, user, { markdown_version: CacheMarkdownField::CACHE_REDCARPET_VERSION })
-    result  = service.execute
-
-    expect(result[:markdown_engine]).to eq :redcarpet
-
-    service = described_class.new(project, user, { markdown_version: CacheMarkdownField::CACHE_COMMONMARK_VERSION })
-    result  = service.execute
-
-    expect(result[:markdown_engine]).to eq :common_mark
-  end
-
-  it 'honors the legacy_render parameter' do
-    service = described_class.new(project, user, { legacy_render: '1' })
-    result  = service.execute
-
-    expect(result[:markdown_engine]).to eq :redcarpet
-  end
 end
diff --git a/spec/services/task_list_toggle_service_spec.rb b/spec/services/task_list_toggle_service_spec.rb
index 750ac4c40ba..cc64dd25085 100644
--- a/spec/services/task_list_toggle_service_spec.rb
+++ b/spec/services/task_list_toggle_service_spec.rb
@@ -3,7 +3,6 @@
 require 'spec_helper'
 
 describe TaskListToggleService do
-  let(:sourcepos) { true }
   let(:markdown) do
     <<-EOT.strip_heredoc
       * [ ] Task 1
@@ -40,87 +39,47 @@ describe TaskListToggleService do
     EOT
   end
 
-  shared_examples 'task lists' do
-    it 'checks Task 1' do
-      toggler = described_class.new(markdown, markdown_html,
-                                    index: 1, toggle_as_checked: true,
-                                    line_source: '* [ ] Task 1', line_number: 1,
-                                    sourcepos: sourcepos)
+  it 'checks Task 1' do
+    toggler = described_class.new(markdown, markdown_html,
+                                  toggle_as_checked: true,
+                                  line_source: '* [ ] Task 1', line_number: 1)
 
-      expect(toggler.execute).to be_truthy
-      expect(toggler.updated_markdown.lines[0]).to eq "* [x] Task 1\n"
-      expect(toggler.updated_markdown_html).to include('disabled checked> Task 1')
-    end
-
-    it 'unchecks Item 1' do
-      toggler = described_class.new(markdown, markdown_html,
-                                    index: 3, toggle_as_checked: false,
-                                    line_source: '1. [X] Item 1', line_number: 6,
-                                    sourcepos: sourcepos)
-
-      expect(toggler.execute).to be_truthy
-      expect(toggler.updated_markdown.lines[5]).to eq "1. [ ] Item 1\n"
-      expect(toggler.updated_markdown_html).to include('disabled> Item 1')
-    end
-
-    it 'returns false if line_source does not match the text' do
-      toggler = described_class.new(markdown, markdown_html,
-                                    index: 2, toggle_as_checked: false,
-                                    line_source: '* [x] Task Added', line_number: 2,
-                                    sourcepos: sourcepos)
-
-      expect(toggler.execute).to be_falsey
-    end
+    expect(toggler.execute).to be_truthy
+    expect(toggler.updated_markdown.lines[0]).to eq "* [x] Task 1\n"
+    expect(toggler.updated_markdown_html).to include('disabled checked> Task 1')
+  end
 
-    it 'returns false if markdown is nil' do
-      toggler = described_class.new(nil, markdown_html,
-                                    index: 2, toggle_as_checked: false,
-                                    line_source: '* [x] Task Added', line_number: 2,
-                                    sourcepos: sourcepos)
+  it 'unchecks Item 1' do
+    toggler = described_class.new(markdown, markdown_html,
+                                  toggle_as_checked: false,
+                                  line_source: '1. [X] Item 1', line_number: 6)
 
-      expect(toggler.execute).to be_falsey
-    end
+    expect(toggler.execute).to be_truthy
+    expect(toggler.updated_markdown.lines[5]).to eq "1. [ ] Item 1\n"
+    expect(toggler.updated_markdown_html).to include('disabled> Item 1')
+  end
 
-    it 'returns false if markdown_html is nil' do
-      toggler = described_class.new(markdown, nil,
-                                    index: 2, toggle_as_checked: false,
-                                    line_source: '* [x] Task Added', line_number: 2,
-                                    sourcepos: sourcepos)
+  it 'returns false if line_source does not match the text' do
+    toggler = described_class.new(markdown, markdown_html,
+                                  toggle_as_checked: false,
+                                  line_source: '* [x] Task Added', line_number: 2)
 
-      expect(toggler.execute).to be_falsey
-    end
+    expect(toggler.execute).to be_falsey
   end
 
-  context 'when using sourcepos' do
-    it_behaves_like 'task lists'
+  it 'returns false if markdown is nil' do
+    toggler = described_class.new(nil, markdown_html,
+                                  toggle_as_checked: false,
+                                  line_source: '* [x] Task Added', line_number: 2)
+
+    expect(toggler.execute).to be_falsey
   end
 
-  context 'when using checkbox indexing' do
-    let(:sourcepos) { false }
-    let(:markdown_html) do
-      <<-EOT.strip_heredoc
-      <ul class="task-list" dir="auto">
-        <li class="task-list-item">
-          <input type="checkbox" class="task-list-item-checkbox" disabled> Task 1
-        </li>
-        <li class="task-list-item">
-          <input type="checkbox" class="task-list-item-checkbox" disabled checked> Task 2
-        </li>
-      </ul>
-      <p dir="auto">A paragraph</p>
-      <ol class="task-list" dir="auto">
-        <li class="task-list-item">
-          <input type="checkbox" class="task-list-item-checkbox" disabled checked> Item 1
-          <ul class="task-list">
-            <li class="task-list-item">
-              <input type="checkbox" class="task-list-item-checkbox" disabled> Sub-item 1
-            </li>
-          </ul>
-        </li>
-      </ol>
-      EOT
-    end
+  it 'returns false if markdown_html is nil' do
+    toggler = described_class.new(markdown, nil,
+                                  toggle_as_checked: false,
+                                  line_source: '* [x] Task Added', line_number: 2)
 
-    it_behaves_like 'task lists'
+    expect(toggler.execute).to be_falsey
   end
 end