fix: Fix WeekOfYear plugin bug while using BadMutable plugin (#884)

src/plugin/weekOfYear/index.js

@@ -1,24 +1,25 @@
 import { MS, Y, D, W } from '../../constant'
 
-export default (o, c) => {
+export default (o, c, d) => {
   const proto = c.prototype
   proto.week = function (week = null) {
     if (week !== null) {
       return this.add((week - this.week()) * 7, D)
     }
     const yearStart = this.$locale().yearStart || 1
     if (this.month() === 11 && this.date() > 25) {
-      const nextYearStartDay = this.startOf(Y).add(1, Y).date(yearStart)
-      const thisEndOfWeek = this.endOf(W)
+      // d(this) is for badMutable
+      const nextYearStartDay = d(this).startOf(Y).add(1, Y).date(yearStart)
+      const thisEndOfWeek = d(this).endOf(W)
       if (nextYearStartDay.isBefore(thisEndOfWeek)) {
         return 1
       }
     }
-    const yearStartDay = this.startOf(Y).date(yearStart)
+    const yearStartDay = d(this).startOf(Y).date(yearStart)
     const yearStartWeek = yearStartDay.startOf(W).subtract(1, MS)
     const diffInWeek = this.diff(yearStartWeek, W, true)
     if (diffInWeek < 0) {
-      return this.startOf('week').week()
+      return d(this).startOf('week').week()
     }
     return Math.ceil(diffInWeek)
   }

test/plugin/badMutable.test.js

@@ -2,9 +2,11 @@ import MockDate from 'mockdate'
 import moment from 'moment'
 import dayjs from '../../src'
 import badMutable from '../../src/plugin/badMutable'
+import weekOfYear from '../../src/plugin/weekOfYear'
 import '../../src/locale/zh-cn'
 
 dayjs.extend(badMutable)
+dayjs.extend(weekOfYear)
 
 beforeEach(() => {
   MockDate.set(new Date())
@@ -175,3 +177,10 @@ it('isAfter isBefore isSame', () => {
   expect(d.format()).toBe(format)
   expect(d.isAfter()).toBe(false)
 })
+
+it('WeekOfYear get week won"t change instance', () => {
+  const d = dayjs()
+  const format = d.format()
+  d.week()
+  expect(d.format()).toBe(format)
+})