Resolve "When editing a comment in an issue, the preview mode is toggled in the main textarea"

app/assets/javascripts/vue_shared/components/markdown/header.vue

@@ -27,20 +27,22 @@
       $(document).off('markdown-preview:hide.vue', this.writeMarkdownTab);
     },
     methods: {
-      isMarkdownForm(form) {
-        return form && !form.find('.js-vue-markdown-field').length;
+      isValid(form) {
+        return !form ||
+          form.find('.js-vue-markdown-field').length ||
+          $(this.$el).closest('form') === form[0];
       },
 
       previewMarkdownTab(event, form) {
         if (event.target.blur) event.target.blur();
-        if (this.isMarkdownForm(form)) return;
+        if (!this.isValid(form)) return;
 
         this.$emit('preview-markdown');
       },
 
       writeMarkdownTab(event, form) {
         if (event.target.blur) event.target.blur();
-        if (this.isMarkdownForm(form)) return;
+        if (!this.isValid(form)) return;
 
         this.$emit('write-markdown');
       },

changelogs/unreleased/44697-prevue.yml

+---
+title: Make toggle markdown preview shortcut only toggle selected field
+merge_request:
+author:
+type: fixed

spec/javascripts/vue_shared/components/markdown/header_spec.js

 import Vue from 'vue';
+import $ from 'jquery';
 import headerComponent from '~/vue_shared/components/markdown/header.vue';
 
 describe('Markdown field header component', () => {
   let vm;
 
-  beforeEach((done) => {
+  beforeEach(done => {
     const Component = Vue.extend(headerComponent);
 
     vm = new Component({
@@ -17,24 +18,18 @@ describe('Markdown field header component', () => {
   });
 
   it('renders markdown buttons', () => {
-    expect(
-      vm.$el.querySelectorAll('.js-md').length,
-    ).toBe(7);
+    expect(vm.$el.querySelectorAll('.js-md').length).toBe(7);
   });
 
   it('renders `write` link as active when previewMarkdown is false', () => {
-    expect(
-      vm.$el.querySelector('li:nth-child(1)').classList.contains('active'),
-    ).toBeTruthy();
+    expect(vm.$el.querySelector('li:nth-child(1)').classList.contains('active')).toBeTruthy();
   });
 
-  it('renders `preview` link as active when previewMarkdown is true', (done) => {
+  it('renders `preview` link as active when previewMarkdown is true', done => {
     vm.previewMarkdown = true;
 
     Vue.nextTick(() => {
-      expect(
-        vm.$el.querySelector('li:nth-child(2)').classList.contains('active'),
-      ).toBeTruthy();
+      expect(vm.$el.querySelector('li:nth-child(2)').classList.contains('active')).toBeTruthy();
 
       done();
     });
@@ -52,16 +47,24 @@ describe('Markdown field header component', () => {
     expect(vm.$emit).toHaveBeenCalledWith('write-markdown');
   });
 
-  it('blurs preview link after click', (done) => {
+  it('does not emit toggle markdown event when triggered from another form', () => {
+    spyOn(vm, '$emit');
+
+    $(document).triggerHandler('markdown-preview:show', [
+      $('<form><textarea class="markdown-area"></textarea></textarea></form>'),
+    ]);
+
+    expect(vm.$emit).not.toHaveBeenCalled();
+  });
+
+  it('blurs preview link after click', done => {
     const link = vm.$el.querySelector('li:nth-child(2) a');
     spyOn(HTMLElement.prototype, 'blur');
 
     link.click();
 
     setTimeout(() => {
-      expect(
-        link.blur,
-      ).toHaveBeenCalled();
+      expect(link.blur).toHaveBeenCalled();
 
       done();
     });