Escape autocomplete results for Markdown

app/assets/javascripts/gfm_auto_complete.js

@@ -54,6 +54,7 @@ class GfmAutoComplete {
       alias: 'commands',
       searchKey: 'search',
       skipSpecialCharacterTest: true,
+      skipMarkdownCharacterTest: true,
       data: GfmAutoComplete.defaultLoadingData,
       displayTpl(value) {
         if (GfmAutoComplete.isLoading(value)) return GfmAutoComplete.Loading.template;
@@ -376,15 +377,23 @@ class GfmAutoComplete {
         return $.fn.atwho.default.callbacks.filter(query, data, searchKey);
       },
       beforeInsert(value) {
-        let resultantValue = value;
+        let withoutAt = value.substring(1);
+        const at = value.charAt();
+
         if (value && !this.setting.skipSpecialCharacterTest) {
-          const withoutAt = value.substring(1);
-          const regex = value.charAt() === '~' ? /\W|^\d+$/ : /\W/;
+          const regex = at === '~' ? /\W|^\d+$/ : /\W/;
           if (withoutAt && regex.test(withoutAt)) {
-            resultantValue = `${value.charAt()}"${withoutAt}"`;
+            withoutAt = `"${withoutAt}"`;
           }
         }
-        return resultantValue;
+
+        // We can ignore this for quick actions because they are processed
+        // before Markdown.
+        if (!this.setting.skipMarkdownCharacterTest) {
+          withoutAt = withoutAt.replace(/([~\-_*`])/g, '\\$&');
+        }
+
+        return `${at}${withoutAt}`;
       },
       matcher(flag, subtext) {
         const match = GfmAutoComplete.defaultMatcher(flag, subtext, this.app.controllers);

changelogs/unreleased/escape-autocomplete-values-for-markdown.yml

+---
+title: Escape Markdown characters properly when using autocomplete
+merge_request:
+author:
+type: fixed

spec/javascripts/gfm_auto_complete_spec.js

@@ -81,13 +81,21 @@ describe('GfmAutoComplete', function () {
     });
 
     it('should quote if value contains any non-alphanumeric characters', () => {
-      expect(beforeInsert(atwhoInstance, '~label-20')).toBe('~"label-20"');
+      expect(beforeInsert(atwhoInstance, '~label-20')).toBe('~"label\\-20"');
       expect(beforeInsert(atwhoInstance, '~label 20')).toBe('~"label 20"');
     });
 
     it('should quote integer labels', () => {
       expect(beforeInsert(atwhoInstance, '~1234')).toBe('~"1234"');
     });
+
+    it('should escape Markdown emphasis characters, except in the first character', () => {
+      expect(beforeInsert(atwhoInstance, '@_group')).toEqual('@\\_group');
+      expect(beforeInsert(atwhoInstance, '~_bug')).toEqual('~\\_bug');
+      expect(beforeInsert(atwhoInstance, '~a `bug`')).toEqual('~"a \\`bug\\`"');
+      expect(beforeInsert(atwhoInstance, '~a ~bug')).toEqual('~"a \\~bug"');
+      expect(beforeInsert(atwhoInstance, '~a **bug')).toEqual('~"a \\*\\*bug"');
+    });
   });
 
   describe('DefaultOptions.matcher', function () {