From 3af36ca02adecd4d1215fb814c7b1b34bef7b5b4 Mon Sep 17 00:00:00 2001
From: iamkun <kunhello@outlook.com>
Date: Fri, 6 Nov 2020 10:47:37 +0800
Subject: [PATCH] fix: fix utc plugin diff edge case

---
 src/plugin/utc/index.js | 2 +-
 test/display.test.js    | 4 ++++
 test/plugin/utc.test.js | 4 ++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/plugin/utc/index.js b/src/plugin/utc/index.js
index 5fb049793..b5b5f4e64 100644
--- a/src/plugin/utc/index.js
+++ b/src/plugin/utc/index.js
@@ -112,7 +112,7 @@ export default (option, Dayjs, dayjs) => {
   }
   const oldDiff = proto.diff
   proto.diff = function (input, units, float) {
-    if (this.$u === input.$u) {
+    if (input && this.$u === input.$u) {
       return oldDiff.call(this, input, units, float)
     }
     const localThis = this.local()
diff --git a/test/display.test.js b/test/display.test.js
index 42975c3cb..7eb48fe82 100644
--- a/test/display.test.js
+++ b/test/display.test.js
@@ -215,6 +215,10 @@ describe('Difference', () => {
     expect(dayjs('2018-08-08').diff(dayjs('2018-09-08'), 'month')).toEqual(-1)
     expect(dayjs('2018-01-01').diff(dayjs('2018-01-01'), 'month')).toEqual(0)
   })
+
+  it('undefined edge case', () => {
+    expect(dayjs().diff(undefined, 'seconds')).toBeDefined()
+  })
 })
 
 it('Unix Timestamp (milliseconds)', () => {
diff --git a/test/plugin/utc.test.js b/test/plugin/utc.test.js
index 7ef563cd9..af046cfea 100644
--- a/test/plugin/utc.test.js
+++ b/test/plugin/utc.test.js
@@ -266,3 +266,7 @@ it('utc keepLocalTime', () => {
   expect(dd).toEqual(dm)
   expect(vd).toEqual(vm)
 })
+
+it('utc diff undefined edge case', () => {
+  expect(dayjs().diff(undefined, 'seconds')).toBeDefined()
+})