From 344bdc0eed6843edb05723dc7853a41833d88f08 Mon Sep 17 00:00:00 2001
From: iamkun <kunhello@outlook.com>
Date: Thu, 7 Jan 2021 00:09:22 +0800
Subject: [PATCH] fix: fix weekYear plugin missing locale bug (#1319)

* fix: fix weekYear plugin missing locale bug

fix #1304
---
 src/plugin/weekYear/index.js |  3 +++
 test/plugin/weekYear.test.js | 23 +++++++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/plugin/weekYear/index.js b/src/plugin/weekYear/index.js
index 1fa7577b7..b7a93e0d5 100644
--- a/src/plugin/weekYear/index.js
+++ b/src/plugin/weekYear/index.js
@@ -7,6 +7,9 @@ export default (o, c) => {
     if (weekOfYear === 1 && month === 11) {
       return year + 1
     }
+    if (month === 0 && weekOfYear >= 52) {
+      return year - 1
+    }
     return year
   }
 }
diff --git a/test/plugin/weekYear.test.js b/test/plugin/weekYear.test.js
index a23709e50..30955d267 100644
--- a/test/plugin/weekYear.test.js
+++ b/test/plugin/weekYear.test.js
@@ -3,6 +3,7 @@ import MockDate from 'mockdate'
 import dayjs from '../../src'
 import weekYear from '../../src/plugin/weekYear'
 import weekOfYear from '../../src/plugin/weekOfYear'
+import '../../src/locale/en-gb'
 
 dayjs.extend(weekYear)
 dayjs.extend(weekOfYear)
@@ -24,7 +25,25 @@ it('Week Year', () => {
   ]
   daySet.forEach((d) => {
     const [day, result] = d
-    expect(dayjs(day).weekYear()).toBe(result)
-    expect(dayjs(day).weekYear()).toBe(moment(day).weekYear())
+    const dResult = dayjs(day).weekYear()
+    expect(dResult).toBe(result)
+    expect(dResult).toBe(moment(day).weekYear())
+  })
+})
+
+it('yearStart: 4', () => {
+  const daySet = [
+    ['2020-12-31', 2020],
+    ['2021-01-01', 2020],
+    ['2021-01-02', 2020],
+    ['2021-01-03', 2020],
+    ['2021-01-04', 2021],
+    ['2021-01-05', 2021]
+  ]
+  daySet.forEach((d) => {
+    const [day, result] = d
+    const dResult = dayjs(day).locale('en-gb').weekYear()
+    expect(dResult).toBe(result)
+    expect(dResult).toBe(moment(day).locale('en-gb').weekYear())
   })
 })