feat: support allow_false for default filter, see #435

docs/source/filters/default.md

@@ -44,4 +44,23 @@ Output
 2.99
 ```
 
+## Allowing `false`
+
+{% since %}v9.32.0{% endsince %}
+
+To allow variables to return `false` instead of the default value, you can use the `allow_false` parameter.
+
+Input
+
+```liquid
+{% assign display_price = false %}
+{{ display_price | default: true, allow_false: true }}
+```
+
+Output
+
+```text
+false
+```
+
 [falsy]: ../tutorials/truthy-and-falsy.html

docs/source/zh-cn/filters/default.md

@@ -42,4 +42,23 @@ title: default
 2.99
 ```
 
+## 允许 `false`
+
+{% since %}v9.32.0{% endsince %}
+
+为了允许让 `false` 直接输出而不是用默认值，可以用 `allow_false` 参数。
+
+输入
+
+```liquid
+{% assign display_price = false %}
+{{ display_price | default: true, allow_false: true }}
+```
+
+输出
+
+```text
+false
+```
+
 [falsy]: ../tutorials/truthy-and-falsy.html

src/builtin/filters/object.ts

@@ -2,10 +2,13 @@ import { isFalsy } from '../../render/boolean'
 import { isArray, isString, toValue } from '../../util/underscore'
 import { FilterImpl } from '../../template/filter/filter-impl'
 
-export function Default<T1, T2> (this: FilterImpl, v: string | T1, arg: T2): string | T1 | T2 {
-  if (isArray(v) || isString(v)) return v.length ? v : arg
-  return isFalsy(toValue(v), this.context) ? arg : v
+export function Default<T1 extends boolean, T2> (this: FilterImpl, value: T1, defaultValue: T2, ...args: Array<[string, any]>): T1 | T2 {
+  if (isArray(value) || isString(value)) return value.length ? value : defaultValue
+  value = toValue(value)
+  if (value === false && (new Map(args)).get('allow_false')) return false as T1
+  return isFalsy(value, this.context) ? defaultValue : value
 }
-export function json (v: any) {
-  return JSON.stringify(v)
+
+export function json (value: any) {
+  return JSON.stringify(value)
 }

test/integration/builtin/filters/object.ts

@@ -12,6 +12,9 @@ describe('filters/object', function () {
     it('undefined should use default', async () => expect(await liquid.parseAndRender('{{not_defined | default: "a"}}')).to.equal('a'))
     it('true should not use default', async () => expect(await liquid.parseAndRender('{{true | default: "a"}}')).to.equal('true'))
     it('0 should not use default', async () => expect(await liquid.parseAndRender('{{0 | default: "a"}}')).to.equal('0'))
+    it('should output false when allow_false=true', async () => expect(await liquid.parseAndRender('{{false | default: true, allow_false: true}}')).to.equal('false'))
+    it('should output default without allow_false', async () => expect(await liquid.parseAndRender('{{false | default: true}}')).to.equal('true'))
+    it('should output default when allow_false=false', async () => expect(await liquid.parseAndRender('{{false | default: true, allow_false: false}}')).to.equal('true'))
   })
   describe('json', function () {
     it('should stringify string', async () => expect(await liquid.parseAndRender('{{"foo" | json}}')).to.equal('"foo"'))