Keep input data after creating existing tag

app/controllers/projects/tags_controller.rb

@@ -38,6 +38,8 @@ class Projects::TagsController < Projects::ApplicationController
       redirect_to namespace_project_tag_path(@project.namespace, @project, @tag.name)
     else
       @error = result[:message]
+      @message = params[:message]
+      @release_description = params[:release_description]
       render action: 'new'
     end
   end

app/views/projects/_zen.html.haml

 - @gfm_form = true
+- current_text ||= nil
 - supports_slash_commands = local_assigns.fetch(:supports_slash_commands, false)
 .zen-backdrop
   - classes << ' js-gfm-input js-autosize markdown-area'
   - if defined?(f) && f
     = f.text_area attr, class: classes, placeholder: placeholder, data: { supports_slash_commands: supports_slash_commands }
   - else
-    = text_area_tag attr, nil, class: classes, placeholder: placeholder
+    = text_area_tag attr, current_text, class: classes, placeholder: placeholder
   %a.zen-control.zen-control-leave.js-zen-leave{ href: "#" }
     = icon('compress')

app/views/projects/tags/new.html.haml

@@ -22,14 +22,14 @@
   .form-group
     = label_tag :message, nil, class: 'control-label'
     .col-sm-10
-      = text_area_tag :message, nil, required: false, tabindex: 3, class: 'form-control', rows: 5
+      = text_area_tag :message, @message, required: false, tabindex: 3, class: 'form-control', rows: 5
       .help-block Optionally, add a message to the tag.
   %hr
   .form-group
     = label_tag :release_description, 'Release notes', class: 'control-label'
     .col-sm-10
       = render layout: 'projects/md_preview', locals: { url: preview_markdown_path(@project), referenced_users: true } do
-        = render 'projects/zen', attr: :release_description, classes: 'note-textarea', placeholder: "Write your release notes or drag files here..."
+        = render 'projects/zen', attr: :release_description, classes: 'note-textarea', placeholder: "Write your release notes or drag files here...", current_text: @release_description
         = render 'shared/notes/hints'
       .help-block Optionally, add release notes to the tag. They will be stored in the GitLab database and displayed on the tags page.
   .form-actions

changelogs/unreleased/31625-tag-editor-loses-all-inputs-when-you-try-to-add-a-tag-that-already-exists.yml

+---
+title: Keep input data after creating a tag that already exists
+merge_request: 11155
+author: