From 4554cbedb26bdbe232a9cebaf4521a4c1afe987c Mon Sep 17 00:00:00 2001
From: imwh0im <soc06103@gmail.com>
Date: Tue, 6 Jul 2021 01:46:29 +0900
Subject: [PATCH] fix: advancedFormat plugin invalid date check

---
 src/plugin/advancedFormat/index.js | 7 ++++++-
 test/plugin/advancedFormat.test.js | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/plugin/advancedFormat/index.js b/src/plugin/advancedFormat/index.js
index 6ebd3f43b..5b1591071 100644
--- a/src/plugin/advancedFormat/index.js
+++ b/src/plugin/advancedFormat/index.js
@@ -1,4 +1,4 @@
-import { FORMAT_DEFAULT } from '../../constant'
+import { FORMAT_DEFAULT, INVALID_DATE_STRING } from '../../constant'
 
 export default (o, c, d) => { // locale needed later
   const proto = c.prototype
@@ -11,6 +11,11 @@ export default (o, c, d) => { // locale needed later
   // extend en locale here
   proto.format = function (formatStr) {
     const locale = this.$locale()
+
+    if (!this.isValid()) {
+      return locale.invalidDate || INVALID_DATE_STRING
+    }
+    
     const utils = this.$utils()
     const str = formatStr || FORMAT_DEFAULT
     const result = str.replace(/\[([^\]]+)]|Q|wo|ww|w|WW|W|zzz|z|gggg|GGGG|Do|X|x|k{1,2}|S/g, (match) => {
diff --git a/test/plugin/advancedFormat.test.js b/test/plugin/advancedFormat.test.js
index d9512e086..955f94032 100644
--- a/test/plugin/advancedFormat.test.js
+++ b/test/plugin/advancedFormat.test.js
@@ -24,6 +24,10 @@ afterEach(() => {
   MockDate.reset()
 })
 
+it('Format of invalid date', () => {
+  expect(dayjs(null).format('z').toLowerCase()).toEqual(moment(null).format('z').toLowerCase())
+})
+
 it('Format empty string', () => {
   expect(dayjs().format()).toBe(moment().format())
 })