fix: null date should return empty (#868) (#872)

Author: timbze

src/filters/date.ts

@@ -45,7 +45,9 @@ function parseDate (v: string | Date, opts: NormalizedFullOptions, timezoneOffse
   const defaultTimezoneOffset = timezoneOffset ?? opts.timezoneOffset
   const locale = opts.locale
   v = toValue(v)
-  if (v === 'now' || v === 'today') {
+  if (isNil(v)) {
+    return undefined
+  } else if (v === 'now' || v === 'today') {
     date = new LiquidDate(Date.now(), locale, defaultTimezoneOffset)
   } else if (isNumber(v)) {
     date = new LiquidDate(v * 1000, locale, defaultTimezoneOffset)

test/integration/filters/date.spec.ts

@@ -21,8 +21,12 @@ describe('filters/date', function () {
       const time = String(new Date('2017-03-07T12:00:00').getTime() / 1000)
       return test('{{ time | date: "%Y-%m-%dT%H:%M:%S" }}', { time }, '2017-03-07T12:00:00')
     })
-    it('should treat nil as 0', () => {
-      expect(liquid.parseAndRenderSync('{{ nil | date: "%Y-%m-%dT%H:%M:%S", "Asia/Shanghai" }}')).toEqual('1970-01-01T08:00:00')
+    it('should treat null as invalid', () => {
+      const time = null
+      return test('{{ time | date: "%Y-%m-%dT%H:%M:%S" }}', { time }, '')
+    })
+    it('should treat nil as invalid', () => {
+      expect(liquid.parseAndRenderSync('{{ nil | date: "%Y-%m-%dT%H:%M:%S", "Asia/Shanghai" }}')).toEqual('')
     })
     it('should treat undefined as invalid', () => {
       expect(liquid.parseAndRenderSync('{{ num | date: "%Y-%m-%dT%H:%M:%S", "Asia/Shanghai" }}', { num: undefined })).toEqual('')