Fix gfm pasting of custom emoji

app/assets/javascripts/behaviors/markdown/nodes/emoji.js

@@ -26,6 +26,18 @@ export default class Emoji extends Node {
             moji: el.textContent,
           }),
         },
+        {
+          tag: 'img.emoji',
+          getAttrs: (el) => {
+            const name = el.getAttribute('title').replace(/^:|:$/g, '');
+
+            return {
+              name,
+              title: name,
+              moji: name,
+            };
+          },
+        },
       ],
       toDOM: (node) => [
         'gl-emoji',

app/assets/javascripts/behaviors/markdown/nodes/image.js

@@ -29,7 +29,7 @@ export default class Image extends BaseImage {
         },
         // Matches HTML generated by Banzai::Filter::ImageLazyLoadFilter
         {
-          tag: 'img[src]',
+          tag: 'img[src]:not(.emoji)',
           getAttrs: (el) => {
             const imageSrc = el.src;
             const imageUrl =

spec/features/markdown/copy_as_gfm_spec.rb

@@ -201,6 +201,15 @@ RSpec.describe 'Copy as GFM', :js do
         GFM
       )
 
+      aggregate_failures('CustomEmojiFilter') do
+        gfm = ':custom_emoji:'
+
+        html = '<img class="emoji" src="custom_emoji.svg" title=":custom_emoji:" height="20" width="20">'
+
+        output_gfm = html_to_gfm(html)
+        expect(output_gfm.strip).to eq(gfm.strip)
+      end
+
       aggregate_failures('MathFilter: math as transformed from HTML to KaTeX') do
         gfm = '$`c = \pm\sqrt{a^2 + b^2}`$'