fix: update devHelper add warning "passing Year as a Number will be parsed as a Unix timestamp"

src/plugin/devHelper/index.js

@@ -8,6 +8,9 @@ export default (o, c, d) => {
       if (typeof date === 'string' && date.length === 13) {
         console.warn(`To parse a Unix timestamp like ${date}, you should pass it as a Number. https://day.js.org/docs/en/parse/unix-timestamp-milliseconds`)
       }
+      if (typeof date === 'number' && String(date).length === 4) {
+        console.warn(`Guessing you may want to parse the Year ${date}, you should pass it as a String ${date}, not a Number. Otherwise, ${date} will be treated as a Unix timestamp`)
+      }
       if (cfg.args.length >= 2 && !d.p.customParseFormat) {
         console.warn(`To parse a date-time string like ${date} using the given format, you should enable customParseFormat plugin first. https://day.js.org/docs/en/parse/string-format`)
       }

test/plugin/devHelper.test.js

@@ -0,0 +1,34 @@
+import MockDate from 'mockdate'
+import dayjs from '../../src'
+import devHelper from '../../src/plugin/devHelper'
+
+dayjs.extend(devHelper)
+
+beforeEach(() => {
+  MockDate.set(new Date())
+})
+
+afterEach(() => {
+  MockDate.reset()
+})
+
+global.console.warn = jest.genMockFunction()
+
+
+it('Warning: passing Year as a Number will be parsed as a Unix timestamp', () => {
+  const consoleSpy = jest.spyOn(console, 'warn')
+  dayjs(2020)
+  expect(consoleSpy).toHaveBeenCalledWith('Guessing you may want to parse the Year 2020, you should pass it as a String 2020, not a Number. Otherwise, 2020 will be treated as a Unix timestamp')
+})
+
+it('Warning Passing Unix timestamp as a String not Number', () => {
+  const consoleSpy = jest.spyOn(console, 'warn')
+  dayjs('1231231231231')
+  expect(consoleSpy).toHaveBeenCalledWith('To parse a Unix timestamp like 1231231231231, you should pass it as a Number. https://day.js.org/docs/en/parse/unix-timestamp-milliseconds')
+})
+
+it('Warning Enable customParseFormat plugin while passing the second format parameter', () => {
+  const consoleSpy = jest.spyOn(console, 'warn')
+  dayjs('2020', 'YYYY')
+  expect(consoleSpy).toHaveBeenCalledWith('To parse a date-time string like 2020 using the given format, you should enable customParseFormat plugin first. https://day.js.org/docs/en/parse/string-format')
+})