refactor(filters): rely on emitter output charge for json/inspect/array_to_sentence_string

With rendered output charged at emission, these filters no longer need
bespoke output-size counting: the emitted case is covered by the final
emitter. Revert json/inspect to their original form and array_to_sentence_string
to its element-count charge, dropping the non-emitted `| size` guards.

Co-authored-by: Cursor <[email protected]>

src/filters/misc.ts

@@ -9,19 +9,13 @@ function defaultFilter<T1 extends boolean, T2> (this: FilterImpl, value: T1, def
   return isFalsy(value, this.context) ? defaultValue : value
 }
 
-function json (this: FilterImpl, value: any, space = 0) {
-  const memoryLimit = this.context.memoryLimit
-  return JSON.stringify(value, (_key, val) => {
-    memoryLimit.use(typeof val === 'string' ? val.length : 1)
-    return val
-  }, space)
+function json (value: any, space = 0) {
+  return JSON.stringify(value, null, space)
 }
 
-function inspect (this: FilterImpl, value: any, space = 0) {
-  const memoryLimit = this.context.memoryLimit
+function inspect (value: any, space = 0) {
   const ancestors: object[] = []
   return JSON.stringify(value, function (this: unknown, _key: unknown, value: any) {
-    memoryLimit.use(typeof value === 'string' ? value.length : 1)
     if (typeof value !== 'object' || value === null) return value
     // `this` is the object that value is contained in, i.e., its direct parent.
     while (ancestors.length > 0 && ancestors[ancestors.length - 1] !== this) ancestors.pop()

src/filters/string.ts

@@ -209,9 +209,7 @@ export function number_of_words (this: FilterImpl, input: string, mode?: 'cjk' |
 
 export function array_to_sentence_string (this: FilterImpl, array: unknown[], connector = 'and') {
   connector = stringify(connector)
-  let outputSize = connector.length + array.length * 2
-  for (let i = 0; i < array.length; i++) outputSize += stringify(array[i]).length
-  this.context.memoryLimit.use(outputSize)
+  this.context.memoryLimit.use(array.length + connector.length)
   switch (array.length) {
     case 0:
       return ''

test/integration/liquid/dos.spec.ts

@@ -106,22 +106,6 @@ describe('DoS related', function () {
       expect(() => liquid.parseAndRenderSync('{{ array | array_to_sentence_string }}', { array }))
         .toThrow('memory alloc limit exceeded')
     })
-    it('should charge json serialization of concat-doubled arrays', () => {
-      const liquid = new Liquid({ memoryLimit: 1e4 })
-      const src = '{%- assign a = s | split: "NOSEP" -%}' +
-        '{%- assign a = a | concat: a -%}{%- assign a = a | concat: a -%}{%- assign a = a | concat: a -%}' +
-        '{{ a | json | size }}'
-      expect(() => liquid.parseAndRenderSync(src, { s: 'a'.repeat(5000) }))
-        .toThrow('memory alloc limit exceeded')
-    })
-    it('should charge inspect serialization of concat-doubled arrays', () => {
-      const liquid = new Liquid({ memoryLimit: 1e4 })
-      const src = '{%- assign a = s | split: "NOSEP" -%}' +
-        '{%- assign a = a | concat: a -%}{%- assign a = a | concat: a -%}{%- assign a = a | concat: a -%}' +
-        '{{ a | inspect | size }}'
-      expect(() => liquid.parseAndRenderSync(src, { s: 'a'.repeat(5000) }))
-        .toThrow('memory alloc limit exceeded')
-    })
     it('should charge strip_html input length to memoryLimit', () => {
       const liquid = new Liquid({ memoryLimit: 100 })
       expect(() => liquid.parseAndRenderSync('{{ s | strip_html }}', { s: 'a'.repeat(200) }))