Changes for review comments

app/services/issuable_base_service.rb

@@ -266,18 +266,18 @@ class IssuableBaseService < BaseService
     update_task_params = params.delete(:update_task)
     return unless update_task_params
 
-    toggler = TaskListToggleService.new(issuable.description, issuable.description_html,
+    tasklist_toggler = TaskListToggleService.new(issuable.description, issuable.description_html,
                                                  line_source: update_task_params[:line_source],
                                                  line_number: update_task_params[:line_number],
-                                        currently_checked: !update_task_params[:checked],
+                                                 toggle_as_checked: update_task_params[:checked],
                                                  index: update_task_params[:index],
                                                  sourcepos: !issuable.legacy_markdown?)
 
-    if toggler.execute
+    if tasklist_toggler.execute
       # by updating the description_html field at the same time,
       # the markdown cache won't be considered invalid
-      params[:description]      = toggler.updated_markdown
-      params[:description_html] = toggler.updated_markdown_html
+      params[:description]      = tasklist_toggler.updated_markdown
+      params[:description_html] = tasklist_toggler.updated_markdown_html
 
       # since we're updating a very specific line, we don't care whether
       # the `lock_version` sent from the FE is the same or not.  Just

app/services/task_list_toggle_service.rb

@@ -11,10 +11,10 @@
 class TaskListToggleService
   attr_reader :updated_markdown, :updated_markdown_html
 
-  def initialize(markdown, markdown_html, line_source:, line_number:, currently_checked:, index:, sourcepos: true)
+  def initialize(markdown, markdown_html, line_source:, line_number:, toggle_as_checked:, index:, sourcepos: true)
     @markdown, @markdown_html  = markdown, markdown_html
     @line_source, @line_number = line_source, line_number
-    @currently_checked         = currently_checked
+    @toggle_as_checked         = toggle_as_checked
     @index, @use_sourcepos     = index, sourcepos
 
     @updated_markdown, @updated_markdown_html = nil
@@ -23,40 +23,45 @@ class TaskListToggleService
   def execute
     return false unless markdown && markdown_html
 
-    !!(toggle_markdown && toggle_html)
+    !!(toggle_markdown && toggle_markdown_html)
   end
 
   private
 
-  attr_reader :markdown, :markdown_html, :index, :currently_checked
+  attr_reader :markdown, :markdown_html, :index, :toggle_as_checked
   attr_reader :line_source, :line_number, :use_sourcepos
 
   def toggle_markdown
     source_lines      = markdown.split("\n")
-    markdown_task = source_lines[line_number - 1]
+    source_line_index = line_number - 1
+    markdown_task     = source_lines[source_line_index]
 
     return unless markdown_task == line_source
     return unless source_checkbox = Taskable::ITEM_PATTERN.match(markdown_task)
 
-    if TaskList::Item.new(source_checkbox[1]).complete?
-      markdown_task.sub!(Taskable::COMPLETE_PATTERN, '[ ]') if currently_checked
+    currently_checked = TaskList::Item.new(source_checkbox[1]).complete?
+
+    # Check `toggle_as_checked` to make sure we don't accidentally replace
+    # any `[ ]` or `[x]` in the middle of the text
+    if currently_checked
+      markdown_task.sub!(Taskable::COMPLETE_PATTERN, '[ ]') unless toggle_as_checked
     else
-      markdown_task.sub!(Taskable::INCOMPLETE_PATTERN, '[x]') unless currently_checked
+      markdown_task.sub!(Taskable::INCOMPLETE_PATTERN, '[x]') if toggle_as_checked
     end
 
-    source_lines[line_number - 1] = markdown_task
+    source_lines[source_line_index] = markdown_task
     @updated_markdown = source_lines.join("\n")
   end
 
-  def toggle_html
+  def toggle_markdown_html
     html          = Nokogiri::HTML.fragment(markdown_html)
     html_checkbox = get_html_checkbox(html)
     return unless html_checkbox
 
-    if currently_checked
-      html_checkbox.remove_attribute('checked')
-    else
+    if toggle_as_checked
       html_checkbox[:checked] = 'checked'
+    else
+      html_checkbox.remove_attribute('checked')
     end
 
     @updated_markdown_html = html.to_html

changelogs/unreleased/19745-forms-with-task-lists-can-be-overwritten-when-editing-simultaneously.yml

 ---
-title: Increase reliability and performance of clicking task items
+title: Increase reliability and performance of toggling task items
 merge_request: 23938
 author:
 type: fixed