Fixes the markdown toolbar buttons

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55618

app/assets/javascripts/lib/utils/text_markdown.js

@@ -82,7 +82,7 @@ export function insertMarkdownText({
   tag,
   cursorOffset,
   blockTag,
-  selected,
+  selected = '',
   wrap,
   select,
 }) {
@@ -212,7 +212,7 @@ export function addMarkdownListeners(form) {
         blockTag: $this.data('mdBlock'),
         wrap: !$this.data('mdPrepend'),
         select: $this.data('mdSelect'),
-        tagContent: $this.data('mdTagContent').toString(),
+        tagContent: $this.data('mdTagContent'),
       });
     });
 }

changelogs/unreleased/markdown-toolbar-btn-fix.yml

@@ -0,0 +1,5 @@
+---
+title: Fixed markdown toolbar buttons
+merge_request:
+author:
+type: fixed

spec/features/issues/user_creates_issue_spec.rb

@@ -14,7 +14,7 @@ describe "User creates issue" do
       visit(new_project_issue_path(project))
     end
 
-    it "creates issue" do
+    it "creates issue", :js do
       page.within(".issue-form") do
         expect(page).to have_no_content("Assign to")
         .and have_no_content("Labels")
@@ -27,11 +27,15 @@ describe "User creates issue" do
       issue_title = "500 error on profile"
 
       fill_in("Title", with: issue_title)
+      first('.js-md').click
+      first('.qa-issuable-form-description').native.send_keys('Description')
+
       click_button("Submit issue")
 
       expect(page).to have_content(issue_title)
         .and have_content(user.name)
         .and have_content(project.name)
+      expect(page).to have_selector('strong', text: 'Description')
     end
   end