fix: avoid blocking first input event in IE when it shouldn't (#9297)

- the original bug in #7138 only happens for `<textarea>`
- the bug doesn't happen if placeholder has empty value

fix #9042, fix #9383

src/platforms/web/runtime/modules/attrs.js

@@ -98,8 +98,8 @@ function baseSetAttr (el, key, value) {
     /* istanbul ignore if */
     if (
       isIE && !isIE9 &&
-      (el.tagName === 'TEXTAREA' || el.tagName === 'INPUT') &&
-      key === 'placeholder' && !el.__ieph
+      el.tagName === 'TEXTAREA' &&
+      key === 'placeholder' && value !== '' && !el.__ieph
     ) {
       const blocker = e => {
         e.stopImmediatePropagation()

test/unit/features/directives/model-text.spec.js

@@ -437,8 +437,8 @@ describe('Directive v-model text', () => {
     })
   }
 
-  // #7138
   if (isIE && !isIE9) {
+    // #7138
     it('should not fire input on initial render of textarea with placeholder in IE10/11', done => {
       const el = document.createElement('div')
       document.body.appendChild(el)
@@ -452,5 +452,21 @@ describe('Directive v-model text', () => {
         done()
       }, 17)
     })
+
+    // #9042
+    it('should not block the first input event when placeholder is empty', done => {
+      const el = document.createElement('div')
+      document.body.appendChild(el)
+      const vm = new Vue({
+        el,
+        data: { evtCount: 0 },
+        template: `<textarea placeholder="" @input="evtCount++"></textarea>`,
+      })
+      triggerEvent(vm.$el, 'input')
+      setTimeout(() => {
+        expect(vm.evtCount).toBe(1)
+        done()
+      }, 17)
+    })
   }
 })