Fix duplicate related issue reference inserted when using autocomplete

Fix https://gitlab.com/gitlab-org/gitlab-ee/issues/2914

app/assets/javascripts/issuable/related_issues/components/add_issuable_form.vue

@@ -85,12 +85,12 @@ export default {
   mounted() {
     const $input = $(this.$refs.input);
-    new GfmAutoComplete(this.autoCompleteSources).setup($input, {
+    this.gfmAutoComplete = new GfmAutoComplete(this.autoCompleteSources);
+    this.gfmAutoComplete.setup($input, {
       issues: true,
     });
     $input.on('shown-issues.atwho', this.onAutoCompleteToggled.bind(this, true));
     $input.on('hidden-issues.atwho', this.onAutoCompleteToggled.bind(this, false));
-    $input.on('inserted-issues.atwho', this.onInput);
     this.$refs.input.focus();
   },

spec/javascripts/issuable/related_issues/components/add_issuable_form_spec.js

@@ -198,6 +198,32 @@ describe('AddIssuableForm', () => {
       });
     });
+    it('when using the autocomplete', (done) => {
+      const $input = $(vm.$refs.input);
+
+      vm.gfmAutoComplete.loadData($input, '#', [{
+        id: 1,
+        iid: 111,
+        title: 'foo',
+      }]);
+
+      $input
+        .val('#')
+        .trigger('input')
+        .trigger('click');
+
+      $('.atwho-container li').trigger('click');
+
+      setTimeout(() => {
+        Vue.nextTick(() => {
+          expect(vm.$refs.input.value).toEqual('');
+          expect(addIssuableFormInputSpy.calls.count()).toEqual(1);
+
+          done();
+        });
+      });
+    });
+
     it('when submitting pending issues', () => {
       expect(addIssuableFormSubmitSpy).not.toHaveBeenCalled();