Fix copy markdown w/ elements with no text content

Copying and pasting markdown content
wasn’t working for DOM elements which
have no text content, eg: image tag.

This commit will fix it.

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

@@ -327,7 +327,10 @@ export const getSelectedFragment = restrictToNode => {
       documentFragment.originalNodes.push(range.commonAncestorContainer);
     }
   }
-  if (documentFragment.textContent.length === 0) return null;
+
+  if (documentFragment.textContent.length === 0 && documentFragment.children.length === 0) {
+    return null;
+  }
 
   return documentFragment;
 };

changelogs/unreleased/24020-copy-markdown-from-comments.yml

+---
+title: Fix copy markdown with elements with no text content
+merge_request: 24020
+author:
+type: fixed

spec/javascripts/behaviors/shortcuts/shortcuts_issuable_spec.js

@@ -52,6 +52,7 @@ describe('ShortcutsIssuable', function() {
         return documentFragment;
       });
     };
+
     describe('with empty selection', () => {
       it('does not return an error', () => {
         ShortcutsIssuable.replyWithSelectedText(true);
@@ -297,5 +298,18 @@ describe('ShortcutsIssuable', function() {
         });
       });
     });
+
+    describe('with a valid selection with no text content', () => {
+      it('returns the proper markdown', done => {
+        stubSelection('<img src="foo" alt="image" />');
+        ShortcutsIssuable.replyWithSelectedText(true);
+
+        setTimeout(() => {
+          expect($(FORM_SELECTOR).val()).toBe('> ![image](http://localhost:9876/foo)\n\n');
+
+          done();
+        });
+      });
+    });
   });
 });