Fix( unit ): using the. exact modifier error when all system modifiers

src/compiler/codegen/events.js

@@ -130,12 +130,17 @@ function genHandler (handler: ASTElementHandler | Array<ASTElementHandler>): str
         }
       } else if (key === 'exact') {
         const modifiers: ASTModifiers = (handler.modifiers: any)
-        genModifierCode += genGuard(
-          ['ctrl', 'shift', 'alt', 'meta']
-            .filter(keyModifier => !modifiers[keyModifier])
-            .map(keyModifier => `$event.${keyModifier}Key`)
-            .join('||')
+        const modifiersKey = ['ctrl', 'shift', 'alt', 'meta'].filter(
+          keyModifier => !modifiers[keyModifier]
         )
+
+        if (modifiersKey.length) {
+          genModifierCode += genGuard(
+            modifiersKey
+              .map(keyModifier => `$event.${keyModifier}Key`)
+              .join('||')
+          )
+        }
       } else {
         keys.push(key)
       }

test/unit/features/directives/on.spec.js

@@ -307,6 +307,29 @@ describe('Directive v-on', () => {
     expect(spy.calls.count()).toBe(1)
   })
 
+  it('should support exact modifier when use all modifers', () => {
+    vm = new Vue({
+      el,
+      template: `
+        <div>
+          <input ref="ctrl" @keyup.ctrl.alt.shift.meta.exact="foo">
+        </div>
+      `,
+      methods: { foo: spy }
+    })
+
+    triggerEvent(vm.$refs.ctrl, 'keyup')
+    expect(spy.calls.count()).toBe(0)
+
+    triggerEvent(vm.$refs.ctrl, 'keyup', e => {
+      e.ctrlKey = true
+      e.altKey = true
+      e.shiftKey = true
+      e.metaKey = true
+    })
+    expect(spy.calls.count()).toBe(1)
+  })
+
   it('should support number keyCode', () => {
     vm = new Vue({
       el,