feat: remove memoryLimit; add templateLimit, outputLengthLimit, maxDepth (#937)

* feat: remove memoryLimit option (#910)

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

* feat: add templateLimit, outputLengthLimit, and maxDepth DoS limits

Enforce v11 resource guards in render and tags, fix for offset/else behavior, and update tutorials for Tag-class registration.

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

* docs: revert unnecessary tutorial churn from memoryLimit PR

Restore the two-example register-filters-tags structure (Value + Hash)
and undo unrelated constructor/emitter doc edits not required for DoS limits.

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

* docs: trim security-model prose and update render-tag-content

Remove diary-style engine comparisons from security-model.md.
Update render-tag-content tutorial to Tag class examples with tpls class field.

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

* docs: note maxDepth stack overflow applies to renderSync only

Explain why async render does not need maxDepth for stack protection based on generator/toPromise driving.

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

* refactor: track maxDepth via depthLimit Limiter on Context

Replace increaseDepth/decreaseDepth with a shared Limiter that supports
paired use/release, matching templateLimit and outputLengthLimit patterns.

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

* fix: remove spurious diff noise in filter files

Restore misc.ts from origin/next with LF line endings and re-apply only
memoryLimit removal, avoiding CRLF and blank-line churn in the export block.

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

* refactor: minimize PR diff noise

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

* feat: cap strftime pad width at 1M

docs: restructure security model with production guidance
Co-authored-by: Cursor <[email protected]>

* refactor: simplify depthLimit in partial tags and tighten security docs

Drop try/finally around depthLimit in include, layout, and render; release at generator end. Consolidate production guidance in security-model.md. Fix padded-blocks lint in dos.spec.ts.

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

---------

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

docs/source/tutorials/options.md

@@ -140,6 +140,8 @@ It defaults to `false`. For example, when set to `true`, a blank string would ev
 
 **ownPropertyOnly** hides scope variables from prototypes, useful when you're passing a not sanitized object into LiquidJS or need to hide prototypes from templates. Defaults to `true`.
 
+Built-in DoS limits and host isolation guidance are documented in [Security Model](./security-model.html).
+
 {% note info Nonexistent Tags %}
 Nonexistent tags always throw errors during parsing and this behavior cannot be customized.
 {% endnote %}

docs/source/tutorials/render-tag-content.md

@@ -22,7 +22,7 @@ Expected output:
 </div>
 ```
 
-Firstly, [register][register-tags] a tag named `wrap` and parse the content into `this.tpls`. Here in `parse(tagToken, remainTokens)`:
+Firstly, [register][register-tags] a tag named `wrap` and parse the content into `this.tpls`. In the tag `constructor(tagToken, remainTokens, liquid)`:
 
 - `tagToken` is current token `{%raw%}{% wrap %}{%endraw%}`, and
 - `remainTokens` is an array of all tokens following `{%raw%}{% wrap %}{%endraw%}` until the end of this template file.
@@ -30,9 +30,12 @@ Firstly, [register][register-tags] a tag named `wrap` and parse the content into
 Basically, what we need to do is take/`.shift()` enough tags from `remainTokens` until we get an `endwrap` token (the name can be arbitrary, but by convention it should be `endwrap`). And if there's no `endwrap` until the end of the template file, we need to throw a tag-not-closed `Error`.
 
 ```javascript
-engine.registerTag('wrap', {
+const { Tag } = require('liquidjs')
-  parse(tagToken, remainTokens) {
+
-    this.tpls = []
+engine.registerTag('wrap', class WrapTag extends Tag {
+  tpls = []
+  constructor(tagToken, remainTokens, liquid) {
+    super(tagToken, remainTokens, liquid)
     let closed = false
     while (remainTokens.length) {
       let token = remainTokens.shift()
@@ -44,11 +47,11 @@ engine.registerTag('wrap', {
       // parse token into template
       // parseToken() may consume more than 1 tokens
       // e.g. {% if %}...{% endif %}
-      let tpl = this.liquid.parser.parseToken(token, remainTokens)
+      let tpl = liquid.parser.parseToken(token, remainTokens)
       this.tpls.push(tpl)
     }
     if (!closed) throw new Error(`tag ${tagToken.getText()} not closed`)
-  },
+  }
   * render(context, emitter) {
     emitter.write("<div class='wrapper'>")
     yield this.liquid.renderer.renderTemplates(this.tpls, context, emitter)
@@ -57,16 +60,17 @@ engine.registerTag('wrap', {
 })
 ```
 
-`.renderTemplates()` can be async; we need `yield` to wait for it to complete. For more details on async in LiquidJS, see [Sync and Async][async]. Other parts of the `render()` method are quite straightforward. Here's a JSFiddle version: <https://jsfiddle.net/por0zcn1/3/>
+`.renderTemplates()` can be async; we need `yield` to wait for it to complete. For more details on async in LiquidJS, see [Sync and Async][async]. Here's a JSFiddle version: <https://jsfiddle.net/por0zcn1/3/>
 
 ## Using ParseStream
 
-When it comes to complex tags like [for][for] and [if][if], the `parse()` can be very complicated. There's a [ParseStream][ParseStream] utility to organize the `parse()` in event-based style. Following is a re-written `parse()` using `ParseStream` that does exactly the same as the example above.
+For more complex tags such as [for][for] and [if][if], constructor parsing can get unwieldy. [ParseStream][ParseStream] offers an event-based API for this. The constructor below is equivalent to the example above:
 
 ```javascript
-parse(tagToken, remainTokens) {
+tpls = []
-  this.tpls = []
+constructor(tagToken, remainTokens, liquid) {
-  this.liquid.parser.parseStream(remainTokens)
+  super(tagToken, remainTokens, liquid)
+  liquid.parser.parseStream(remainTokens)
     .on('template', tpl => this.tpls.push(tpl))
     // note that we cannot use arrow function because we need `this`
     .on('tag:endwrap', function () { this.stop() })
@@ -103,15 +107,18 @@ As you've noticed, there's an additional `repeat.i` in the context of `repeat`.
 Each time we enter a new *Context*, we need to push a new *Scope*. And when we finish rendering and exit the *Context*, we pop the *Scope* from the *Context*. As you can see in the following implementation:
 
 ```javascript
-engine.registerTag('repeat', {
+const { Tag } = require('liquidjs')
-  parse(tagToken, remainTokens) {
+
-    this.tpls = []
+engine.registerTag('repeat', class RepeatTag extends Tag {
-    this.liquid.parser.parseStream(remainTokens)
+  tpls = []
+  constructor(tagToken, remainTokens, liquid) {
+    super(tagToken, remainTokens, liquid)
+    liquid.parser.parseStream(remainTokens)
       .on('template', tpl => this.tpls.push(tpl))
       .on('tag:endrepeat', function () { this.stop() })
       .on('end', () => { throw new Error(`tag ${tagToken.getText()} not closed`) })
       .start()
-  },
+  }
   * render(context, emitter) {
     const repeat = { i: 1 }
     context.push({ repeat })
@@ -123,7 +130,7 @@ engine.registerTag('repeat', {
 })
 ```
 
-The `parse()` is exactly the same as `wrap` tag, we repeat the content simply by calling `.renderTemplates(this.tpls)` twice during `render()`. Here's the JSFiddle: <https://jsfiddle.net/por0zcn1/2/>
+The constructor is the same as in the `wrap` tag; we repeat the content by calling `.renderTemplates(this.tpls)` twice during `render()`. Here's the JSFiddle: <https://jsfiddle.net/por0zcn1/2/>
 
 {% note warn Use Push & Pop in Pairs %}
 `context.push()` and `context.pop()` have to be used in pairs. Failing to `pop()` the *Scope* you pushed will leak the *Scope* to latter templates and may corrupt the *Context* stack.

docs/source/tutorials/security-model.md

@@ -2,21 +2,19 @@
 title: Security Model
 ---
 
-LiquidJS provides DoS-oriented limits (`parseLimit`, `renderLimit`, `memoryLimit`) to reduce risk. This page summarizes those limits, [`ownPropertyOnly`][ownPropertyOnly], custom [`Drop`][drop] usage, and the security boundary to assume in production.
+LiquidJS provides DoS-oriented limits (`parseLimit`, `templateLimit`, `outputLengthLimit`, `maxDepth`) to reduce risk. This page summarizes those limits, [`ownPropertyOnly`][ownPropertyOnly], custom [`Drop`][drop] usage, and the security boundary to assume in production.
 
-## Security boundary
+## At a glance
 
-The built-in limits are cooperative safeguards, not strict runtime isolation.
+LiquidJS ships a thin cooperative DoS layer:
-
-- They do **not** equal process RSS/heap usage.
-- They do **not** sandbox JavaScript execution.
-- They should be combined with process/container limits and request timeouts for defense in depth.
-
-## Limits at a glance
 
 - [parseLimit][parseLimit]: limit total template size per `parse()` call.
-- [renderLimit][renderLimit]: limit total render time per `render()` call.
+- [templateLimit][templateLimit]: limit total tag/HTML/output nodes rendered per `render()` call.
-- [memoryLimit][memoryLimit]: cooperatively limit memory-sensitive allocations counted by LiquidJS.
+- [outputLengthLimit][outputLengthLimit]: limit total output length per `render()` call.
+- [maxDepth][maxDepth]: limit nesting depth of `{% render %}`, `{% include %}`, and `{% layout %}`.
+- Strftime numeric pad widths in the `date` filter are capped at `1_000_000` (1M) per conversion.
+
+These are cooperative safeguards, not runtime isolation—see [Production guidance](#production-guidance) below for host-level limits and online-service hardening.
 
 ## Limit details
 
@@ -26,9 +24,9 @@ The built-in limits are cooperative safeguards, not strict runtime isolation.
 
 A typical PC handles `1e8` (100M) characters without issues.
 
-### renderLimit
+### templateLimit
 
-Restricting template size alone is insufficient because dynamic loops with large counts can occur during rendering. [renderLimit][renderLimit] mitigates this by limiting the time consumed by each `render()` call.
+Restricting template size alone is insufficient because dynamic loops with large counts can occur during rendering. [templateLimit][templateLimit] mitigates this by limiting the number of tag, HTML literal, and output nodes rendered in each `render()` call.
 
 ```liquid
 {%- for i in (1..10000000) -%}
@@ -36,29 +34,19 @@ Restricting template size alone is insufficient because dynamic loops with large
 {%- endfor -%}
 ```
 
-Render time is checked on a per-template basis (before rendering each template). In the above example, there are 2 templates in the loop: `order: ` and `{{i}}`, render time will be checked 10000000x2 times.
+Each template node (the `for` tag, literal `order: `, output `{{i}}`, and so on) counts toward the limit. In the above example, a limit of `30000000` would be exceeded before the loop finishes.
 
-`renderLimit` is not a hard CPU limiter. It is checked between template renders, so compute-intensive filters/tags/user-defined functions or deeply nested template execution between checks can still cause DoS.
+`templateLimit` is checked before each node render, so compute-intensive filters/tags/user-defined functions between checks can still cause DoS.
 
-### memoryLimit
+### outputLengthLimit
 
-`memoryLimit` only limits operations that LiquidJS explicitly counts.
+[outputLengthLimit][outputLengthLimit] caps the cumulative length of output written during a `render()` call, including output from partials rendered via `{% render %}`.
 
-- Counted: memory-sensitive LiquidJS operations that call internal memory accounting.
+### maxDepth
-- Not guaranteed counted: arbitrary user object behavior such as custom `toValue()`/`toString()` chains, or other host-side code that allocates outside LiquidJS accounting points.
 
-In other words, `memoryLimit` limits what LiquidJS counts, not every byte your process may allocate.
+[maxDepth][maxDepth] limits how deeply `{% render %}`, `{% include %}`, and `{% layout %}` can nest. Defaults to `128`. In sync rendering (`renderSync`), nested tags are driven by `toValueSync`, which recursively resumes each yielded generator on the call stack—deep nesting can overflow it, and `maxDepth` caps that depth. Async `render()` resumes the same tag generators via `toPromise`/`yield` without a deep synchronous call chain, so stack overflow is not a concern there (the limit still applies as a DoS guard).
 
-Even with a small number of templates and iterations, memory usage can grow exponentially. In the following example, memory doubles with each iteration:
+The `memoryLimit` option was removed in v11; enforce memory limits at the host or process level instead.
-
-```liquid
-{% assign array = "1,2,3" | split: "," %}
-{% for i in (1..32) %}
-    {% assign array = array | concat: array %}
-{% endfor %}
-```
-
-As [JavaScript uses GC to manage memory](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Memory_management), `memoryLimit` may not reflect the actual memory footprint.
 
 ## `ownPropertyOnly` and scope data
 
@@ -68,20 +56,21 @@ With [`ownPropertyOnly`][ownPropertyOnly] `true`, plain scope objects only expos
 
 [`Drop`][drop] values are not restricted the same way: LiquidJS still reads the prototype chain and may call [`liquidMethodMissing`][liquidMethodMissing]. **You** control what a drop exposes; narrow APIs and never feed unsafe data into drops unless the class is built for template access. `ownPropertyOnly` alone does not harden custom drops—audit them like any privileged code.
 
-## Online service guidance
+## Production guidance
 
-If you run an online service, avoid rendering fully user-defined templates whenever possible.
+LiquidJS does not sandbox template code—custom filters, tags, and scope helpers run as ordinary JavaScript with your process privileges. Built-in DoS limits are one layer; production deployments, especially online services that accept template input, need additional hardening:
 
-- Prefer curated templates or a restricted template subset.
+- **Prefer curated templates** over fully user-defined Liquid when possible; if users need customization, offer a restricted subset rather than open template editing.
-- If user-defined templates are required, isolate rendering (worker/process/container), enforce OS/container memory and CPU limits, and apply request rate limits.
+- Run each render in a **worker thread or child process** with a wall-clock timeout; **kill** the worker on expiry. Libraries such as [paralleljs][paralleljs] can help for heavy single-template work.
-- Treat `parseLimit`/`renderLimit`/`memoryLimit` as one layer in a broader DoS defense strategy.
+- Enforce **container/Kubernetes cgroup limits**, `ulimit`, or equivalent on the renderer process for memory and CPU.
-
+- Apply **request rate limits** at the API or gateway layer.
-For heavy single-template operations, process-level isolation is still recommended (for example with [paralleljs][paralleljs]).
+- **`node:vm`, `isolated-vm`, and Jinja/Twig-style sandbox modes are not a security boundary**—template logic runs in the same JS runtime as your app, with your privileges.
 
 [paralleljs]: https://www.npmjs.com/package/paralleljs
 [parseLimit]: /api/interfaces/LiquidOptions.html#parseLimit
-[renderLimit]: /api/interfaces/LiquidOptions.html#renderLimit
+[templateLimit]: /api/interfaces/LiquidOptions.html#templateLimit
-[memoryLimit]: /api/interfaces/LiquidOptions.html#memoryLimit
+[outputLengthLimit]: /api/interfaces/LiquidOptions.html#outputLengthLimit
+[maxDepth]: /api/interfaces/LiquidOptions.html#maxDepth
 [ownPropertyOnly]: /api/interfaces/LiquidOptions.html#ownPropertyOnly
 [renderOwnPropertyOnly]: /api/interfaces/RenderOptions.html#ownPropertyOnly
 [strictVariables]: /api/interfaces/LiquidOptions.html#strictVariables

docs/themes/navy/source/js/main.js

@@ -42,8 +42,7 @@
   if (!/\/playground(?:\.html)?$/.test(location.pathname)) return;
   updateVersion(liquidjs.version);
   const engine = new liquidjs.Liquid({
-    memoryLimit: 1e5,
+    templateLimit: 1e5
-    renderLimit: 1e5
   });
   const colorScheme = window.matchMedia('(prefers-color-scheme: dark)');
   const editor = createEditor('editorEl', 'liquid');

src/context/context.ts

@@ -1,4 +1,3 @@
-import { getPerformance } from '../util/performance'
 import { Drop } from '../drop/drop'
 import { __assign } from 'tslib'
 import { NormalizedFullOptions, defaultOptions, RenderOptions } from '../liquid-options'
@@ -36,17 +35,19 @@ export class Context {
    */
   public strictVariables: boolean;
   public ownPropertyOnly: boolean;
-  public memoryLimit: Limiter;
+  public templateLimit: Limiter;
-  public renderLimit: Limiter;
+  public outputLengthLimit: Limiter;
-  public constructor (env: object = {}, opts: NormalizedFullOptions = defaultOptions, renderOptions: RenderOptions = {}, { memoryLimit, renderLimit }: { [key: string]: Limiter } = {}) {
+  public depthLimit: Limiter;
+  public constructor (env: object = {}, opts: NormalizedFullOptions = defaultOptions, renderOptions: RenderOptions = {}, { templateLimit, outputLengthLimit, depthLimit }: { templateLimit?: Limiter, outputLengthLimit?: Limiter, depthLimit?: Limiter } = {}) {
     this.sync = !!renderOptions.sync
     this.opts = opts
     this.globals = renderOptions.globals ?? opts.globals
     this.environments = isObject(env) ? env : Object(env)
     this.strictVariables = renderOptions.strictVariables ?? this.opts.strictVariables
     this.ownPropertyOnly = renderOptions.ownPropertyOnly ?? opts.ownPropertyOnly
-    this.memoryLimit = memoryLimit ?? new Limiter('memory alloc', renderOptions.memoryLimit ?? opts.memoryLimit)
+    this.templateLimit = templateLimit ?? new Limiter('template', renderOptions.templateLimit ?? opts.templateLimit)
-    this.renderLimit = renderLimit ?? new Limiter('template render', getPerformance().now() + (renderOptions.renderLimit ?? opts.renderLimit))
+    this.outputLengthLimit = outputLengthLimit ?? new Limiter('output length', renderOptions.outputLengthLimit ?? opts.outputLengthLimit)
+    this.depthLimit = depthLimit ?? new Limiter('template depth', opts.maxDepth)
   }
   public getRegister<T> (key: string, defaultValue: T = undefined as T): T {
     return (this.registers[key] = this.registers[key] || defaultValue)
@@ -109,8 +110,9 @@ export class Context {
       strictVariables: this.strictVariables,
       ownPropertyOnly: this.ownPropertyOnly
     }, {
-      renderLimit: this.renderLimit,
+      templateLimit: this.templateLimit,
-      memoryLimit: this.memoryLimit
+      outputLengthLimit: this.outputLengthLimit,
+      depthLimit: this.depthLimit
     })
   }
   private findScope (key: string | number) {

src/emitters/simple-emitter.ts

@@ -1,10 +1,17 @@
-import { stringify } from '../util'
+import { stringify, Limiter } from '../util'
 import { Emitter } from './emitter'
 
 export class SimpleEmitter implements Emitter {
   public buffer = '';
+  private outputLengthLimit?: Limiter
+
+  constructor (outputLengthLimit?: Limiter) {
+    this.outputLengthLimit = outputLengthLimit
+  }
 
   public write (html: any) {
-    this.buffer += stringify(html)
+    const str = stringify(html)
+    this.outputLengthLimit?.use(str.length)
+    this.buffer += str
   }
 }

src/emitters/streamed-emitter.ts

@@ -1,12 +1,20 @@
-import { stringify } from '../util'
+import { stringify, Limiter } from '../util'
 import { Emitter } from './emitter'
 import { PassThrough } from 'stream'
 
 export class StreamedEmitter implements Emitter {
   public buffer = '';
   public stream: NodeJS.ReadWriteStream = new PassThrough()
+  private outputLengthLimit?: Limiter
+
+  constructor (outputLengthLimit?: Limiter) {
+    this.outputLengthLimit = outputLengthLimit
+  }
+
   public write (html: any) {
-    this.stream.write(stringify(html))
+    const str = stringify(html)
+    this.outputLengthLimit?.use(str.length)
+    this.stream.write(str)
   }
   public error (err: Error) {
     this.stream.emit('error', err)

src/filters/array.ts

@@ -8,9 +8,6 @@ import { EmptyDrop } from '../drop'
 export const join = argumentsToValue(function (this: FilterImpl, v: any[], arg: string) {
   const array = toArray(v)
   const sep = isNil(arg) ? ' ' : stringify(arg)
-  let outputSize = sep.length * Math.max(array.length - 1, 0)
-  for (let i = 0; i < array.length; i++) outputSize += String(array[i]).length
-  this.context.memoryLimit.use(outputSize)
   return Array.prototype.join.call(array, sep)
 })
 export const last = argumentsToValue(function (this: FilterImpl, v: any) {
@@ -21,14 +18,12 @@ export const first = argumentsToValue(function (this: FilterImpl, v: any) {
 })
 export const reverse = argumentsToValue(function (this: FilterImpl, v: any[]) {
   const array = toArray(v)
-  this.context.memoryLimit.use(array.length)
   return [...array].reverse()
 })
 
 function * sortBy<T> (this: FilterImpl, arr: T[], property: string | undefined, comparator: (a: unknown, b: unknown) => number): IterableIterator<unknown> {
   const values: [T, unknown][] = []
   const array = toArray(arr)
-  this.context.memoryLimit.use(array.length)
   for (const item of array) {
     values.push([
       item,
@@ -51,7 +46,6 @@ export const size = (v: string | any[]) => v?.length || 0
 export function * map (this: FilterImpl, arr: Scope[], property: string): IterableIterator<unknown> {
   const results = []
   const array = toArray(arr)
-  this.context.memoryLimit.use(array.length)
   for (const item of array) {
     results.push(yield this.context._getFromScope(item, stringify(property), false))
   }
@@ -70,14 +64,12 @@ export function * sum (this: FilterImpl, arr: Scope[], property?: string): Itera
 
 export function compact<T> (this: FilterImpl, arr: T[]) {
   const array = toArray(arr)
-  this.context.memoryLimit.use(array.length)
   return Array.prototype.filter.call(array, x => !isNil(toValue(x)))
 }
 
 export function concat<T1, T2> (this: FilterImpl, v: T1[], arg: T2[] = []): (T1 | T2)[] {
   const lhs = toArray(v)
   const rhs = toArray(arg)
-  this.context.memoryLimit.use(lhs.length + rhs.length)
   return Array.prototype.concat.call(lhs, rhs)
 }
 
@@ -87,7 +79,6 @@ export function push<T> (this: FilterImpl, v: T[], arg: T): T[] {
 
 export function unshift<T> (this: FilterImpl, v: T[], arg: T): T[] {
   const array = toArray(v)
-  this.context.memoryLimit.use(array.length)
   const clone = [...array]
   clone.unshift(arg)
   return clone
@@ -95,7 +86,6 @@ export function unshift<T> (this: FilterImpl, v: T[], arg: T): T[] {
 
 export function pop<T> (this: FilterImpl, v: T[]): T[] {
   const array = toArray(v)
-  this.context.memoryLimit.use(array.length)
   const clone = [...array]
   clone.pop()
   return clone
@@ -103,7 +93,6 @@ export function pop<T> (this: FilterImpl, v: T[]): T[] {
 
 export function shift<T> (this: FilterImpl, v: T[]): T[] {
   const array = toArray(v)
-  this.context.memoryLimit.use(array.length)
   const clone = [...array]
   clone.shift()
   return clone
@@ -114,7 +103,6 @@ export function slice<T> (this: FilterImpl, v: T[] | string, begin: number, leng
   if (isNil(v)) return []
   if (!isArray(v)) v = stringify(v)
   begin = begin < 0 ? v.length + begin : begin
-  this.context.memoryLimit.use(length)
   return isArray(v)
     ? Array.prototype.slice.call(v, begin, begin + length)
     : String.prototype.slice.call(v, begin, begin + length)
@@ -133,7 +121,6 @@ function expectedMatcher (this: FilterImpl, expected: any): (v: any) => boolean
 function * filter<T extends object> (this: FilterImpl, include: boolean, arr: T[], property: string, expected: any): IterableIterator<unknown> {
   const values: unknown[] = []
   arr = toArray(arr)
-  this.context.memoryLimit.use(arr.length)
   const token = new Tokenizer(stringify(property)).readScopeValue()
   for (const item of arr) {
     values.push(yield evalToken(token, this.context.spawn(item)))
@@ -146,7 +133,6 @@ function * filter_exp<T extends object> (this: FilterImpl, include: boolean, arr
   const filtered: unknown[] = []
   const keyTemplate = new Value(stringify(exp), this.liquid)
   const array = toArray(arr)
-  this.context.memoryLimit.use(array.length)
   for (const item of array) {
     this.context.push({ [itemName]: item })
     const value = yield keyTemplate.value(this.context)
@@ -176,7 +162,6 @@ export function * group_by<T extends object> (this: FilterImpl, arr: T[], proper
   const map = new Map()
   arr = toEnumerable(arr)
   const token = new Tokenizer(stringify(property)).readScopeValue()
-  this.context.memoryLimit.use(arr.length)
   for (const item of arr) {
     const key = yield evalToken(token, this.context.spawn(item))
     if (!map.has(key)) map.set(key, [])
@@ -189,7 +174,6 @@ export function * group_by_exp<T extends object> (this: FilterImpl, arr: T[], it
   const map = new Map()
   const keyTemplate = new Value(stringify(exp), this.liquid)
   arr = toEnumerable(arr)
-  this.context.memoryLimit.use(arr.length)
   for (const item of arr) {
     this.context.push({ [itemName]: item })
     const key = yield keyTemplate.value(this.context)
@@ -253,7 +237,6 @@ export function * find_exp<T extends object> (this: FilterImpl, arr: T[], itemNa
 
 export function uniq<T> (this: FilterImpl, arr: T[]): T[] {
   arr = toArray(arr)
-  this.context.memoryLimit.use(arr.length)
   return [...new Set(arr)]
 }
 
@@ -261,7 +244,6 @@ export function sample<T> (this: FilterImpl, v: T[] | string, count = 1): T | st
   v = toValue(v)
   if (isNil(v)) return []
   if (!isArray(v)) v = stringify(v)
-  this.context.memoryLimit.use(v.length)
   const shuffled = [...v].sort(() => Math.random() - 0.5)
   if (count === 1) return shuffled[0]
   return shuffled.slice(0, count)

src/filters/base64.ts

@@ -10,16 +10,13 @@ import { base64Encode, base64Decode } from './base64-impl'
 
 export function base64_encode (this: FilterImpl, value: string | Buffer): string {
   if (typeof Buffer !== 'undefined' && Buffer.isBuffer(value)) {
-    this.context.memoryLimit.use(value.byteLength)
     return value.toString('base64')
   }
   const str = stringify(value)
-  this.context.memoryLimit.use(str.length)
   return base64Encode(str)
 }
 
 export function base64_decode (this: FilterImpl, value: string): string {
   const str = stringify(value)
-  this.context.memoryLimit.use(str.length)
   return base64Decode(str)
 }

src/filters/crypto.ts

@@ -10,13 +10,11 @@ import { sha256 as sha256Impl, hmacSha256 as hmacSha256Impl } from './crypto-imp
 
 export function sha256 (this: FilterImpl, value: unknown): string | Promise<string> {
   const str = stringify(value)
-  this.context.memoryLimit.use(str.length)
   return sha256Impl(str)
 }
 
 export function hmac_sha256 (this: FilterImpl, value: unknown, key: unknown): string | Promise<string> {
   const str = stringify(value)
   const keyStr = stringify(key)
-  this.context.memoryLimit.use(str.length + keyStr.length)
   return hmacSha256Impl(str, keyStr)
 }

src/filters/date.ts

@@ -3,14 +3,11 @@ import { FilterImpl } from '../template'
 import { NormalizedFullOptions } from '../liquid-options'
 
 export function date (this: FilterImpl, v: string | Date, format?: string, timezoneOffset?: number | string) {
-  const size = ((v as string)?.length ?? 0) + ((timezoneOffset as string)?.length ?? 0)
-  this.context.memoryLimit.use(size)
   const date = parseDate(v, this.context.opts, timezoneOffset)
   if (!date) return v
   format = toValue(format)
   format = isNil(format) ? this.context.opts.dateFormat : stringify(format)
-  this.context.memoryLimit.use(format.length)
+  return strftime(date, format)
-  return strftime(date, format, this.context.memoryLimit)
 }
 
 export function date_to_xmlschema (this: FilterImpl, v: string | Date) {
@@ -32,14 +29,13 @@ export function date_to_long_string (this: FilterImpl, v: string | Date, type?:
 function stringify_date (this: FilterImpl, v: string | Date, month_type: string, type?: string, style?: string) {
   const date = parseDate(v, this.context.opts)
   if (!date) return v
-  const ml = this.context.memoryLimit
   if (type === 'ordinal') {
     const d = date.getDate()
     return style === 'US'
-      ? strftime(date, `${month_type} ${d}%q, %Y`, ml)
+      ? strftime(date, `${month_type} ${d}%q, %Y`)
-      : strftime(date, `${d}%q ${month_type} %Y`, ml)
+      : strftime(date, `${d}%q ${month_type} %Y`)
   }
-  return strftime(date, `%d ${month_type} %Y`, ml)
+  return strftime(date, `%d ${month_type} %Y`)
 }
 
 function parseDate (v: string | Date, opts: NormalizedFullOptions, timezoneOffset?: number | string): LiquidDate | undefined {

src/filters/html.ts

@@ -18,7 +18,6 @@ const unescapeMap: Record<string, string> = {
 
 export function escape (this: FilterImpl, str: string) {
   str = stringify(str)
-  this.context.memoryLimit.use(str.length)
   return str.replace(/&|<|>|"|'/g, m => escapeMap[m])
 }
 
@@ -28,7 +27,6 @@ export function xml_escape (this: FilterImpl, str: string) {
 
 function unescape (this: FilterImpl, str: string) {
   str = stringify(str)
-  this.context.memoryLimit.use(str.length)
   return str.replace(/&(amp|lt|gt|#34|#39);/g, m => unescapeMap[m])
 }
 
@@ -38,7 +36,6 @@ export function escape_once (this: FilterImpl, str: string) {
 
 export function newline_to_br (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   return str.replace(/\r?\n/gm, '<br />\n')
 }
 
@@ -46,7 +43,6 @@ export function newline_to_br (this: FilterImpl, v: string) {
 // equivalent is O(n^2) in V8 on unclosed openers.
 export function strip_html (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   const blocks = new Map([['<script', '</script>'], ['<style', '</style>'], ['<!--', '-->'], ['<', '>']])
   let out = ''
   let i = 0

src/filters/misc.ts

@@ -2,18 +2,6 @@ import { isFalsy } from '../render/boolean'
 import { identify, isArray, isString, toValue } from '../util/underscore'
 import { FilterImpl } from '../template'
 
-function chargeJsonReplacerValue (memoryLimit: { use(count: number): void }, val: unknown) {
-  if (typeof val === 'string') {
-    memoryLimit.use(val.length)
-  } else if (val === null || typeof val === 'number' || typeof val === 'boolean') {
-    memoryLimit.use(JSON.stringify(val).length)
-  } else if (Array.isArray(val)) {
-    memoryLimit.use(val.length + 1)
-  } else if (typeof val === 'object') {
-    memoryLimit.use(2)
-  }
-}
-
 function defaultFilter<T1 extends boolean, T2> (this: FilterImpl, value: T1, defaultValue: T2, ...args: Array<[string, any]>): T1 | T2 {
   value = toValue(value)
   if (isArray(value) || isString(value)) return value.length ? value : defaultValue
@@ -22,29 +10,21 @@ function defaultFilter<T1 extends boolean, T2> (this: FilterImpl, value: T1, def
 }
 
 function json (this: FilterImpl, value: any, space = 0) {
-  const memoryLimit = this.context.memoryLimit
+  return JSON.stringify(value, undefined, space)
-  return JSON.stringify(value, (_key, val) => {
-    chargeJsonReplacerValue(memoryLimit, val)
-    return val
-  }, space)
 }
 
 function inspect (this: FilterImpl, value: any, space = 0) {
-  const memoryLimit = this.context.memoryLimit
   const ancestors: object[] = []
   return JSON.stringify(value, function (this: unknown, _key: unknown, value: any) {
     if (typeof value !== 'object' || value === null) {
-      chargeJsonReplacerValue(memoryLimit, value)
       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()
     if (ancestors.includes(value)) {
-      memoryLimit.use('[Circular]'.length)
       return '[Circular]'
     }
     ancestors.push(value)
-    chargeJsonReplacerValue(memoryLimit, value)
     return value
   }, space)
 }

src/filters/string.ts

@@ -22,7 +22,6 @@ export function append (this: FilterImpl, v: string, arg: string) {
   assert(arguments.length === 2, 'append expect 2 arguments')
   const lhs = stringify(v)
   const rhs = stringify(arg)
-  this.context.memoryLimit.use(lhs.length + rhs.length)
   return lhs + rhs
 }
 
@@ -30,16 +29,13 @@ export function prepend (this: FilterImpl, v: string, arg: string) {
   assert(arguments.length === 2, 'prepend expect 2 arguments')
   const lhs = stringify(v)
   const rhs = stringify(arg)
-  this.context.memoryLimit.use(lhs.length + rhs.length)
   return rhs + lhs
 }
 
 export function lstrip (this: FilterImpl, v: string, chars?: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   if (chars) {
     chars = stringify(chars)
-    this.context.memoryLimit.use(chars.length)
     for (let i = 0, set = new Set(chars); i < str.length; i++) {
       if (!set.has(str[i])) return str.slice(i)
     }
@@ -50,34 +46,29 @@ export function lstrip (this: FilterImpl, v: string, chars?: string) {
 
 export function downcase (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   return str.toLowerCase()
 }
 
 export function upcase (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   return stringify(str).toUpperCase()
 }
 
 export function remove (this: FilterImpl, v: string, arg: string) {
   const str = stringify(v)
   arg = stringify(arg)
-  this.context.memoryLimit.use(str.length + arg.length)
   return str.split(arg).join('')
 }
 
 export function remove_first (this: FilterImpl, v: string, l: string) {
   const str = stringify(v)
   l = stringify(l)
-  this.context.memoryLimit.use(str.length + l.length)
   return str.replace(l, '')
 }
 
 export function remove_last (this: FilterImpl, v: string, l: string) {
   const str = stringify(v)
   const pattern = stringify(l)
-  this.context.memoryLimit.use(str.length + pattern.length)
   const index = str.lastIndexOf(pattern)
   if (index === -1) return str
   return str.substring(0, index) + str.substring(index + pattern.length)
@@ -85,10 +76,8 @@ export function remove_last (this: FilterImpl, v: string, l: string) {
 
 export function rstrip (this: FilterImpl, str: string, chars?: string) {
   str = stringify(str)
-  this.context.memoryLimit.use(str.length)
   if (chars) {
     chars = stringify(chars)
-    this.context.memoryLimit.use(chars.length)
     for (let i = str.length - 1, set = new Set(chars); i >= 0; i--) {
       if (!set.has(str[i])) return str.slice(0, i + 1)
     }
@@ -99,7 +88,6 @@ export function rstrip (this: FilterImpl, str: string, chars?: string) {
 
 export function split (this: FilterImpl, v: string, arg: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   const arr = str.split(stringify(arg))
   // align to ruby split, which is the behavior of shopify/liquid
   // see: https://ruby-doc.org/core-2.4.0/String.html#method-i-split
@@ -109,10 +97,8 @@ export function split (this: FilterImpl, v: string, arg: string) {
 
 export function strip (this: FilterImpl, v: string, chars?: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   if (chars) {
     const set = new Set(stringify(chars))
-    this.context.memoryLimit.use(set.size)
     let i = 0
     let j = str.length - 1
     while (set.has(str[i])) i++
@@ -124,13 +110,11 @@ export function strip (this: FilterImpl, v: string, chars?: string) {
 
 export function strip_newlines (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   return str.replace(/\r?\n/gm, '')
 }
 
 export function capitalize (this: FilterImpl, str: string) {
   str = stringify(str)
-  this.context.memoryLimit.use(str.length)
   return str.charAt(0).toUpperCase() + str.slice(1).toLowerCase()
 }
 
@@ -139,8 +123,6 @@ export function replace (this: FilterImpl, v: string, pattern: string, replaceme
   pattern = stringify(pattern)
   replacement = stringify(replacement)
   const parts = str.split(pattern)
-  const outputSize = str.length + (parts.length - 1) * (replacement.length - pattern.length)
-  this.context.memoryLimit.use(outputSize)
   return parts.join(replacement)
 }
 
@@ -148,7 +130,6 @@ export function replace_first (this: FilterImpl, v: string, arg1: string, arg2:
   const str = stringify(v)
   arg1 = stringify(arg1)
   arg2 = stringify(arg2)
-  this.context.memoryLimit.use(str.length + arg1.length + arg2.length)
   return str.replace(arg1, () => arg2)
 }
 
@@ -156,7 +137,6 @@ export function replace_last (this: FilterImpl, v: string, arg1: string, arg2: s
   const str = stringify(v)
   const pattern = stringify(arg1)
   const replacement = stringify(arg2)
-  this.context.memoryLimit.use(str.length + pattern.length + replacement.length)
   const index = str.lastIndexOf(pattern)
   if (index === -1) return str
   return str.substring(0, index) + replacement + str.substring(index + pattern.length)
@@ -165,7 +145,6 @@ export function replace_last (this: FilterImpl, v: string, arg1: string, arg2: s
 export function truncate (this: FilterImpl, v: string, l = 50, o = '...') {
   const str = stringify(v)
   o = stringify(o)
-  this.context.memoryLimit.use(str.length + o.length)
   if (str.length <= l) return v
   return str.substring(0, l - o.length) + o
 }
@@ -173,7 +152,6 @@ export function truncate (this: FilterImpl, v: string, l = 50, o = '...') {
 export function truncatewords (this: FilterImpl, v: string, words = 15, o = '...') {
   const str = stringify(v)
   o = stringify(o)
-  this.context.memoryLimit.use(str.length + o.length)
   const arr = str.split(/\s+/)
   if (words <= 0) words = 1
   let ret = arr.slice(0, words).join(' ')
@@ -183,13 +161,11 @@ export function truncatewords (this: FilterImpl, v: string, words = 15, o = '...
 
 export function normalize_whitespace (this: FilterImpl, v: string) {
   const str = stringify(v)
-  this.context.memoryLimit.use(str.length)
   return str.replace(/\s+/g, ' ')
 }
 
 export function number_of_words (this: FilterImpl, input: string, mode?: 'cjk' | 'auto') {
   const str = stringify(input)
-  this.context.memoryLimit.use(str.length)
   input = str.trim()
   if (!input) return 0
   switch (mode) {
@@ -209,9 +185,6 @@ 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)
   switch (array.length) {
     case 0:
       return ''

src/liquid-options.ts

@@ -87,10 +87,12 @@ export interface LiquidOptions {
   orderedFilterParameters?: boolean;
   /** For DoS handling, limit total length of templates parsed in one `parse()` call. A typical PC can handle 1e8 (100M) characters without issues. */
   parseLimit?: number;
-  /** For DoS handling, limit total time (in ms) for each `render()` call. */
+  /** For DoS handling, limit total renders of tag/HTML/output in one `render()` call. */
-  renderLimit?: number;
+  templateLimit?: number;
-  /** For DoS handling, limit new objects creation, including array concat/join/strftime, etc. A typical PC can handle 1e9 (1G) memory without issue. */
+  /** For DoS handling, limit total output length in one `render()` call. */
-  memoryLimit?: number;
+  outputLengthLimit?: number;
+  /** For DoS handling, limit nesting depth of `{% render %}`, `{% include %}`, and `{% layout %}` tags. Defaults to `128`. */
+  maxDepth?: number;
 }
 
 export interface RenderOptions {
@@ -110,12 +112,10 @@ export interface RenderOptions {
    * Same as `ownPropertyOnly` on LiquidOptions, but only for current render() call
    */
   ownPropertyOnly?: boolean;
-  /** For DoS handling, limit total renders of tag/HTML/output in one `render()` call. A typical PC can handle 1e5 renders of typical templates per second. */
+  /** For DoS handling, limit total renders of tag/HTML/output in one `render()` call. */
   templateLimit?: number;
-  /** For DoS handling, limit total time (in ms) for each `render()` call. */
+  /** For DoS handling, limit total output length in one `render()` call. */
-  renderLimit?: number;
+  outputLengthLimit?: number;
-  /** For DoS handling, limit new objects creation, including array concat/join/strftime, etc. A typical PC can handle 1e9 (1G) memory without issue.. */
-  memoryLimit?: number;
 }
 
 export interface RenderFileOptions extends RenderOptions {
@@ -160,8 +160,9 @@ export interface NormalizedFullOptions extends NormalizedOptions {
   globals: object;
   operators: Operators;
   parseLimit: number;
-  renderLimit: number;
+  templateLimit: number;
-  memoryLimit: number;
+  outputLengthLimit: number;
+  maxDepth: number;
 }
 
 export const defaultOptions: NormalizedFullOptions = {
@@ -194,9 +195,10 @@ export const defaultOptions: NormalizedFullOptions = {
   lenientIf: false,
   globals: {},
   operators: defaultOperators,
-  memoryLimit: Infinity,
   parseLimit: Infinity,
-  renderLimit: Infinity
+  templateLimit: Infinity,
+  outputLengthLimit: Infinity,
+  maxDepth: 128
 }
 
 export function normalize (options: LiquidOptions): NormalizedFullOptions {

src/render/expression.ts

@@ -67,7 +67,6 @@ export function evalQuotedToken (token: QuotedToken) {
 function * evalRangeToken (token: RangeToken, ctx: Context) {
   const low: number = yield evalToken(token.lhs, ctx)
   const high: number = yield evalToken(token.rhs, ctx)
-  ctx.memoryLimit.use(high - low + 1)
   return range(+low, +high + 1)
 }
 

src/render/render.ts

@@ -1,4 +1,3 @@
-import { getPerformance } from '../util/performance'
 import { toPromise, RenderError, LiquidErrors, LiquidError } from '../util'
 import { Context } from '../context'
 import { Template } from '../template'
@@ -6,23 +5,17 @@ import { Emitter, StreamedEmitter, SimpleEmitter } from '../emitters'
 
 export class Render {
   public renderTemplatesToNodeStream (templates: Template[], ctx: Context): NodeJS.ReadableStream {
-    const emitter = new StreamedEmitter()
+    const emitter = new StreamedEmitter(ctx.outputLengthLimit)
     Promise.resolve().then(() => toPromise(this.renderTemplates(templates, ctx, emitter)))
       .then(() => emitter.end(), err => emitter.error(err))
     return emitter.stream
   }
-  public * renderTemplates (templates: Template[], ctx: Context, emitter?: Emitter): IterableIterator<any> {
+  public * renderTemplates (templates: Template[], ctx: Context, emitter: Emitter = new SimpleEmitter(ctx.outputLengthLimit)): IterableIterator<any> {
-    if (!emitter) {
-      emitter = new SimpleEmitter()
-    }
-    ctx.renderLimit.check(getPerformance().now())
     const errors = []
     for (const tpl of templates) {
-      ctx.renderLimit.check(getPerformance().now())
+      ctx.templateLimit.use(1)
       try {
-        // if tpl.render supports emitter, it'll return empty `html`
         const html = yield tpl.render(ctx, emitter)
-        // if not, it'll return an `html`, write to the emitter for it
         html && emitter.write(html)
         if (ctx.breakCalled || ctx.continueCalled) break
       } catch (e) {

src/tags/for.ts

@@ -43,13 +43,6 @@ export default class extends Tag {
   }
   * render (ctx: Context, emitter: Emitter): Generator<unknown, void | string, Template[]> {
     const r = this.liquid.renderer
-    let collection = toEnumerable(yield evalToken(this.collection, ctx))
-
-    if (!collection.length) {
-      yield r.renderTemplates(this.elseTemplates, ctx, emitter)
-      return
-    }
-
     const continueKey = 'continue-' + this.variable + '-' + this.collection.getText()
     ctx.push(createScope({ continue: ctx.getRegister(continueKey, {}) }))
     const hash = (yield this.hash.render(ctx)) as Record<string, any>
@@ -59,6 +52,7 @@ export default class extends Tag {
       ? Object.keys(hash).filter(x => MODIFIERS.includes(x))
       : MODIFIERS.filter(x => hash[x] !== undefined)
 
+    let collection = toEnumerable(yield evalToken(this.collection, ctx))
     collection = modifiers.reduce((collection, modifier: valueOf<typeof MODIFIERS>) => {
       if (modifier === 'offset') return offset(collection, hash['offset'])
       if (modifier === 'limit') return limit(collection, hash['limit'])
@@ -66,6 +60,14 @@ export default class extends Tag {
     }, collection)
 
     ctx.setRegister(continueKey, (hash['offset'] || 0) + collection.length)
+
+    if (!collection.length) {
+      yield r.renderTemplates(this.elseTemplates, ctx, emitter)
+      return
+    }
+
+    if (!this.templates.length) return
+
     const scope = createScope({ forloop: new ForloopDrop(collection.length, this.collection.getText(), this.variable) })
     ctx.push(scope)
     for (const item of collection) {

src/tags/include.ts

@@ -28,6 +28,7 @@ export default class extends Tag {
     this.hash = new Hash(tokenizer, liquid.options.jekyllInclude || liquid.options.keyValueSeparator)
   }
   * render (ctx: Context, emitter: Emitter): Generator<unknown, void, unknown> {
+    ctx.depthLimit.use(1)
     const { liquid, hash, withVar } = this
     const { renderer } = liquid
     const filepath = (yield renderFilePath(this.file, ctx, liquid)) as string
@@ -43,6 +44,7 @@ export default class extends Tag {
     yield renderer.renderTemplates(templates, ctx, emitter)
     ctx.pop()
     ctx.restoreRegister(saved)
+    ctx.depthLimit.release(1)
   }
 
   public * children (partials: boolean, sync: boolean): Generator<unknown, Template[]> {

src/tags/layout.ts

@@ -26,6 +26,7 @@ export default class extends Tag {
       yield renderer.renderTemplates(this.templates, ctx, emitter)
       return
     }
+    ctx.depthLimit.use(1)
     const filepath = (yield renderFilePath(this.file, ctx, liquid)) as string
     assert(filepath, () => `illegal file path "${filepath}"`)
     const templates = (yield liquid._parseLayoutFile(filepath, ctx.sync, this.currentFile)) as Template[]
@@ -43,6 +44,7 @@ export default class extends Tag {
     ctx.push(createScope((yield args.render(ctx)) as Scope))
     yield renderer.renderTemplates(templates, ctx, emitter)
     ctx.pop()
+    ctx.depthLimit.release(1)
   }
 
   public * children (partials: boolean): Generator<unknown, Template[]> {

src/tags/render.ts

@@ -55,6 +55,7 @@ export default class extends Tag {
     this.hash = new Hash(tokenizer, liquid.options.keyValueSeparator)
   }
   * render (ctx: Context, emitter: Emitter): Generator<unknown, void, unknown> {
+    ctx.depthLimit.use(1)
     const { liquid, hash } = this
     const filepath = (yield renderFilePath(this.file, ctx, liquid)) as string
     assert(filepath, () => `illegal file path "${filepath}"`)
@@ -81,6 +82,7 @@ export default class extends Tag {
       const templates = (yield liquid._parsePartialFile(filepath, childCtx.sync, this.currentFile)) as Template[]
       yield liquid.renderer.renderTemplates(templates, childCtx, emitter)
     }
+    ctx.depthLimit.release(1)
   }
 
   public * children (partials: boolean, sync: boolean): Generator<unknown, Template[]> {

src/tags/tablerow.ts

@@ -45,6 +45,10 @@ export default class extends Tag {
     const limit = (args.limit === undefined) ? collection.length : args.limit
 
     collection = collection.slice(offset, offset + limit)
+    if (!collection.length) return
+
+    if (!this.templates.length) return
+
     const cols = args.cols || collection.length
 
     const r = this.liquid.renderer

src/util/limiter.ts

@@ -14,6 +14,11 @@ export class Limiter {
       this.base += +count
     }
   }
+  release (count: number) {
+    if (+count > 0) {
+      this.base -= +count
+    }
+  }
   check (count: number) {
     if (+count > 0) {
       assert(+count <= this.limit, this.message)

src/util/strftime.spec.ts

@@ -188,6 +188,14 @@ describe('util/strftime', function () {
     it('should have higher priority than H', () => {
       expect(t(then, '%0H')).toBe('03')
     })
+    it('should allow pad width up to MAX_STRFTIME_PAD', () => {
+      expect(t(now, '%100000d').length).toBe(100000)
+      expect(t(now, `%${1_000_000}d`).length).toBe(1_000_000)
+    })
+    it('should throw when pad width exceeds MAX_STRFTIME_PAD', () => {
+      expect(() => t(now, `%${1024 * 1024 + 1}d`)).toThrow('strftime pad width limit exceeded')
+      expect(() => t(now, '%5000000d')).toThrow('strftime pad width limit exceeded')
+    })
   })
   describe('modifier field', () => {
     it('should ignore E modifier', () => {

src/util/strftime.ts

@@ -1,13 +1,15 @@
 import { changeCase, padStart, padEnd } from './underscore'
 import { LiquidDate } from './liquid-date'
-import type { Limiter } from './limiter'
+import { assert } from './assert'
+
+/** Per-conversion numeric width cap for strftime (%N, %15d, …). */
+export const MAX_STRFTIME_PAD = 1024 * 1024
 
 const rFormat = /%([-_0^#:]+)?(\d+)?([EO])?(.)/
 interface FormatOptions {
   flags: Record<string, boolean>;
   width?: string;
   modifier?: string;
-  memoryLimit?: Pick<Limiter, 'use'>;
 }
 
 // prototype extensions
@@ -98,8 +100,8 @@ const formatCodes: Record<string, FormatCodeHandler> = {
   M: (d: LiquidDate) => d.getMinutes(),
   N: (d: LiquidDate, opts: FormatOptions) => {
     const width = Number(opts.width) || 9
+    assertPadWidth(width)
     const str = String(d.getMilliseconds()).slice(0, width)
-    opts.memoryLimit?.use(width - str.length)
     return padEnd(str, width, '0')
   },
   p: (d: LiquidDate) => (d.getHours() < 12 ? 'AM' : 'PM'),
@@ -123,25 +125,29 @@ const formatCodes: Record<string, FormatCodeHandler> = {
 }
 formatCodes.h = formatCodes.b
 
-export function strftime (d: LiquidDate, formatStr: string, memoryLimit?: Pick<Limiter, 'use'>) {
+export function strftime (d: LiquidDate, formatStr: string) {
   let output = ''
   let remaining = formatStr
   let match
   while ((match = rFormat.exec(remaining))) {
     output += remaining.slice(0, match.index)
     remaining = remaining.slice(match.index + match[0].length)
-    output += format(d, match, memoryLimit)
+    output += format(d, match)
   }
   return output + remaining
 }
 
-function format (d: LiquidDate, match: RegExpExecArray, memoryLimit?: Pick<Limiter, 'use'>) {
+function assertPadWidth (width: number) {
+  assert(width <= MAX_STRFTIME_PAD, 'strftime pad width limit exceeded')
+}
+
+function format (d: LiquidDate, match: RegExpExecArray) {
   const [input, flagStr = '', width, modifier, conversion] = match
   const convert = formatCodes[conversion]
   if (!convert) return input
   const flags: Record<string, boolean> = {}
   for (const flag of flagStr) flags[flag] = true
-  let ret = String(convert(d, { flags, width, modifier, memoryLimit }))
+  let ret = String(convert(d, { flags, width, modifier }))
   let padChar = padSpaceChars.has(conversion) ? ' ' : '0'
   let padWidth = Number(width) || padWidths[conversion] || 0
   if (flags['^']) ret = ret.toUpperCase()
@@ -149,6 +155,6 @@ function format (d: LiquidDate, match: RegExpExecArray, memoryLimit?: Pick<Limit
   if (flags['_']) padChar = ' '
   else if (flags['0']) padChar = '0'
   if (flags['-']) padWidth = 0
-  memoryLimit?.use(Number(padWidth) - ret.length)
+  else assertPadWidth(padWidth)
   return padStart(ret, padWidth, padChar)
 }

test/e2e/issues.spec.ts

@@ -519,13 +519,6 @@ describe('Issues', function () {
     const result = engine.parseAndRenderSync(`\n{{ "foo" | pos }}`)
     expect(result).toEqual('\n[2,12] foo')
   })
-  it("memoryLimit doesn't work in for tag #776", () => {
-    const engine = new Liquid({
-      memoryLimit: 1e5
-    })
-    const tpl = `{% for i in (1..1000000000) %} {{'a'}} {% endfor %}`
-    expect(() => engine.parseAndRenderSync(tpl)).toThrow('memory alloc limit exceeded, line:1, col:1')
-  })
   it('group_by_exp fails with object as input #785', () => {
     const site = {
       tags: {

test/integration/filters/date.spec.ts

@@ -204,31 +204,21 @@ describe('filters/date', function () {
       return test('{{ "1990-12-31T23:00:00Z" | date: "%Y-%m-%dT%H:%M:%S" }}', '1991-01-01T04:30:00', undefined, optsWithDateFormat)
     })
   })
-  describe('strftime width / memoryLimit', () => {
+  describe('strftime width', () => {
-    it('should charge memoryLimit for huge numeric strftime widths', () => {
+    it('should honor numeric strftime pad width', () => {
-      const liquid = new Liquid({ memoryLimit: 500 })
+      const liquid = new Liquid()
-      expect(() => liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: '%5000000d' }))
-        .toThrow('memory alloc limit exceeded')
-    })
-    it('should charge memoryLimit for array format PoC', () => {
-      const liquid = new Liquid({ memoryLimit: 50, renderLimit: 1e9 })
-      expect(() => liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: ['a'.repeat(2000000)] }))
-        .toThrow('memory alloc limit exceeded')
-    })
-    it('should charge memoryLimit for object toString format PoC', () => {
-      const liquid = new Liquid({ memoryLimit: 50, renderLimit: 1e9 })
-      const huge = 'a'.repeat(2000000)
-      const f = { toString: () => huge }
-      expect(() => liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f }))
-        .toThrow('memory alloc limit exceeded')
-    })
-    it('should honor numeric strftime pad width when memoryLimit allows', () => {
-      const liquid = new Liquid({ memoryLimit: 1e7 })
       const out = liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: '%5000d' })
       expect(out.length).toBe(5000)
-      const tight = new Liquid({ memoryLimit: 100 })
+    })
-      expect(() => tight.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: '%5000d' }))
+    it('should honor large numeric strftime pad width up to the cap', () => {
-        .toThrow('memory alloc limit exceeded')
+      const liquid = new Liquid()
+      const out = liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: '%100000d' })
+      expect(out.length).toBe(100000)
+    })
+    it('should throw when numeric strftime pad width is too large', () => {
+      const liquid = new Liquid()
+      expect(() => liquid.parseAndRenderSync('{{ d | date: f }}', { d: 'now', f: '%5000000d' }))
+        .toThrow('strftime pad width limit exceeded')
     })
   })
 })

test/integration/liquid/dos.spec.ts

@@ -4,15 +4,18 @@ import { mock, restore } from '../../stub/mockfs'
 describe('DoS related', function () {
   describe('#parseLimit', function () {
     afterEach(restore)
+
     it('should throw when parse limit exceeded', async () => {
       const noLimit = new Liquid()
       const limit10 = new Liquid({ parseLimit: 10 })
       const limit90 = new Liquid({ parseLimit: 90 })
       const template = '{% capture bar %}{{ foo | bar: 3, a[3] }}{% endcapture %}'
+
       await expect(noLimit.parseAndRender(template)).resolves.toBe('')
       await expect(limit10.parseAndRender(template)).rejects.toThrow('parse length limit exceeded')
       await expect(limit90.parseAndRender(template)).resolves.toBe('')
     })
+
     it('should take included template into account', async () => {
       mock({
         '/small': 'Lorem ipsum',
@@ -23,119 +26,151 @@ describe('DoS related', function () {
       await expect(liquid.parseAndRender('{% include "large" %}')).rejects.toThrow('parse length limit exceeded')
     })
   })
-  describe('#renderLimit', () => {
+
+  describe('#templateLimit', () => {
     it('should throw when rendering too many templates', async () => {
       const src = '{% for i in (1..1000) %}{{i}},{% endfor %}'
       const noLimit = new Liquid()
-      const limitSmall = new Liquid({ renderLimit: 0.01 })
+      const limitSmall = new Liquid({ templateLimit: 100 })
-      const limitLarge = new Liquid({ renderLimit: 2e4 })
+      const limitLarge = new Liquid({ templateLimit: 2001 })
       await expect(noLimit.parseAndRender(src)).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
-      await expect(limitSmall.parseAndRender(src)).rejects.toThrow('template render limit exceeded')
+      await expect(limitSmall.parseAndRender(src)).rejects.toThrow('template limit exceeded')
       await expect(limitLarge.parseAndRender(src)).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
     })
+
     it('should support reset when calling render', async () => {
       const src = '{% for i in (1..1000) %}{{i}},{% endfor %}'
-      const liquid = new Liquid({ renderLimit: 0.01 })
+      const liquid = new Liquid({ templateLimit: 100 })
-      await expect(liquid.parseAndRender(src)).rejects.toThrow('template render limit exceeded')
+      await expect(liquid.parseAndRender(src)).rejects.toThrow('template limit exceeded')
-      await expect(liquid.parseAndRender(src, {}, { renderLimit: 1e6 })).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
+      await expect(liquid.parseAndRender(src, {}, { templateLimit: 2001 })).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
     })
+
     it('should take partials into account', async () => {
       mock({
         '/small': '{% for i in (1..5) %}{{i}}{% endfor %}',
         '/large': '{% for i in (1..50000000) %}{{i}}{% endfor %}'
       })
-      const liquid = new Liquid({ root: '/', renderLimit: 1000 })
+      const liquid = new Liquid({ root: '/', templateLimit: 1000 })
-      await expect(liquid.parseAndRender('{% render "large" %}')).rejects.toThrow('template render limit exceeded')
+      await expect(liquid.parseAndRender('{% render "large" %}')).rejects.toThrow('template limit exceeded')
       await expect(liquid.parseAndRender('{% render "small" %}')).resolves.toBe('12345')
     })
-    it('should enforce renderLimit when for body has no template nodes', () => {
-      const liquid = new Liquid({ memoryLimit: 1e9, renderLimit: 1 })
-      expect(() => liquid.parseAndRenderSync('{%- for i in (1..5000000) -%}{%- endfor -%}', {}))
-        .toThrow('template render limit exceeded')
   })
-    it('should enforce renderLimit when tablerow body has no template nodes', () => {
+
-      const liquid = new Liquid({ memoryLimit: 1e9, renderLimit: 1 })
+  describe('#outputLengthLimit', () => {
-      expect(() => liquid.parseAndRenderSync('{%- tablerow i in (1..1000000) cols:1 -%}{%- endtablerow -%}', {}))
+    it('should throw when output length exceeded', async () => {
-        .toThrow('template render limit exceeded')
+      const src = '{% for i in (1..1000) %}{{i}},{% endfor %}'
-    })
+      const noLimit = new Liquid()
-  })
+      const limitSmall = new Liquid({ outputLengthLimit: 10 })
-  describe('#memoryLimit', () => {
+      const limitLarge = new Liquid({ outputLengthLimit: 5000 })
-    it('should throw for too many array creation in filters', async () => {
+      await expect(noLimit.parseAndRender(src)).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
-      const array = Array(1e3).fill(0)
+      await expect(limitSmall.parseAndRender(src)).rejects.toThrow('output length limit exceeded')
-      const liquid = new Liquid({ memoryLimit: 100 })
+      await expect(limitLarge.parseAndRender(src)).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
-      await expect(liquid.parseAndRender('{{ array | slice: 0, 3 | join }}', { array })).resolves.toBe('0 0 0')
-      await expect(liquid.parseAndRender('{{ array | slice: 0, 300 | join }}', { array })).rejects.toThrow('memory alloc limit exceeded, line:1, col:1')
     })
+
     it('should support reset when calling render', async () => {
-      const array = Array(1e3).fill(0)
+      const src = '{% for i in (1..1000) %}{{i}},{% endfor %}'
-      const liquid = new Liquid({ memoryLimit: 100 })
+      const liquid = new Liquid({ outputLengthLimit: 10 })
-      await expect(liquid.parseAndRender('{{ array | slice: 0, 300 | join }}', { array })).rejects.toThrow('memory alloc limit exceeded, line:1, col:1')
+      await expect(liquid.parseAndRender(src)).rejects.toThrow('output length limit exceeded')
-      await expect(liquid.parseAndRender('{{ array | slice: 0, 300 | join }}', { array }, { memoryLimit: 1e3 })).resolves.toBe(Array(300).fill(0).join(' '))
+      await expect(liquid.parseAndRender(src, {}, { outputLengthLimit: 5000 })).resolves.toMatch(/^1,2,3,4,5,.*,999,1000,$/)
     })
-    it('should throw for too many array iteration in tags', async () => {
+
-      const array = ['a']
+    it('should take partials into account', async () => {
-      const liquid = new Liquid({ memoryLimit: 100 })
+      mock({
-      const src = '{% for i in (1..count) %}{% assign array = array | concat: array %}{% endfor %}{{ array | join }}'
+        '/small': 'abc',
-      await expect(liquid.parseAndRender(src, { array, count: 3 })).resolves.toBe('a a a a a a a a')
+        '/large': '{% for i in (1..1000) %}{{i}}{% endfor %}'
-      await expect(liquid.parseAndRender(src, { array, count: 100 })).rejects.toThrow('memory alloc limit exceeded, line:1, col:26')
       })
-    it('should charge pop allocation to memoryLimit', async () => {
+      const liquid = new Liquid({ root: '/', outputLengthLimit: 10 })
-      const array = Array(1e3).fill(0)
+      await expect(liquid.parseAndRender('{% render "small" %}')).resolves.toBe('abc')
-      const liquid = new Liquid({ memoryLimit: 100 })
+      await expect(liquid.parseAndRender('{% render "large" %}')).rejects.toThrow('output length limit exceeded')
-      await expect(liquid.parseAndRender('{{ array | pop | size }}', { array })).rejects.toThrow('memory alloc limit exceeded')
     })
-    it('should charge sample allocation to memoryLimit', async () => {
+
-      const array = Array(1e3).fill(0)
+    it('should enforce outputLengthLimit in sync render', () => {
-      const liquid = new Liquid({ memoryLimit: 100 })
+      const liquid = new Liquid({ outputLengthLimit: 5 })
-      await expect(liquid.parseAndRender('{{ array | sample: 1 | size }}', { array })).rejects.toThrow('memory alloc limit exceeded')
+      expect(() => liquid.parseAndRenderSync('{% for i in (1..100) %}{{i}}{% endfor %}'))
+        .toThrow('output length limit exceeded')
     })
-    it('should charge join by produced output size, not element count', () => {
+
-      const array = ['a'.repeat(100), 'b'.repeat(100)]
+    it('should enforce outputLengthLimit in stream render', async () => {
-      const liquid = new Liquid({ memoryLimit: 100 })
+      const liquid = new Liquid({ outputLengthLimit: 5 })
-      expect(() => liquid.parseAndRenderSync('{{ array | join: "" }}', { array }))
+      const tpl = liquid.parse('{% for i in (1..100) %}{{i}}{% endfor %}')
-        .toThrow('memory alloc limit exceeded')
+      const stream = liquid.renderToNodeStream(tpl)
-    })
+      await expect(new Promise((resolve, reject) => {
-    it('should allow join within memoryLimit', () => {
+        stream.on('error', reject)
-      const array = ['a'.repeat(20), 'b'.repeat(20)]
+        stream.on('end', resolve)
-      const liquid = new Liquid({ memoryLimit: 100 })
+      })).rejects.toThrow('output length limit exceeded')
-      expect(liquid.parseAndRenderSync('{{ array | join: "" }}', { array })).toBe('a'.repeat(20) + 'b'.repeat(20))
-    })
-    it('should prevent concat doubling from bypassing join memoryLimit', () => {
-      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 | join: "" | size }}'
-      expect(() => liquid.parseAndRenderSync(src, { s: 'a'.repeat(5000) }))
-        .toThrow('memory alloc limit exceeded')
-    })
-    it('should charge array_to_sentence_string by produced output size', () => {
-      const array = ['a'.repeat(100), 'b'.repeat(100), 'c'.repeat(100)]
-      const liquid = new Liquid({ memoryLimit: 100 })
-      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) }))
-        .toThrow('memory alloc limit exceeded')
     })
   })
+
+  describe('#maxDepth', () => {
+    function chain (depth: number, tag: string) {
+      const templates: Record<string, string> = {}
+      for (let i = 0; i < depth; i++) {
+        templates[`t${i}`] = i === depth - 1 ? 'done' : `{% ${tag} "t${i + 1}" %}`
+      }
+      return templates
+    }
+
+    it('should throw when include depth exceeded', async () => {
+      const liquid = new Liquid({ templates: chain(3, 'include'), maxDepth: 2 })
+      await expect(liquid.parseAndRender('{% include "t0" %}')).rejects.toThrow('template depth limit exceeded')
+    })
+
+    it('should allow include within maxDepth', async () => {
+      const liquid = new Liquid({ templates: chain(2, 'include'), maxDepth: 2 })
+      await expect(liquid.parseAndRender('{% include "t0" %}')).resolves.toBe('done')
+    })
+
+    it('should throw when render depth exceeded', async () => {
+      const liquid = new Liquid({ templates: chain(3, 'render'), maxDepth: 2 })
+      await expect(liquid.parseAndRender('{% render "t0" %}')).rejects.toThrow('template depth limit exceeded')
+    })
+
+    it('should allow render within maxDepth', async () => {
+      const liquid = new Liquid({ templates: chain(2, 'render'), maxDepth: 2 })
+      await expect(liquid.parseAndRender('{% render "t0" %}')).resolves.toBe('done')
+    })
+
+    it('should throw when layout depth exceeded', async () => {
+      const liquid = new Liquid({
+        templates: {
+          a: '{% layout "b" %}body-a',
+          b: '{% layout "c" %}body-b',
+          c: 'body-c'
+        },
+        maxDepth: 2
+      })
+      await expect(liquid.parseAndRender('{% layout "a" %}root')).rejects.toThrow('template depth limit exceeded')
+    })
+
+    it('should allow layout within maxDepth', async () => {
+      const liquid = new Liquid({
+        templates: {
+          a: '{% layout "b" %}body-a',
+          b: 'body-b'
+        },
+        maxDepth: 2
+      })
+      await expect(liquid.parseAndRender('{% layout "a" %}root')).resolves.toBe('body-b')
+    })
+
+    it('should not count layout none toward depth', async () => {
+      const liquid = new Liquid({ maxDepth: 0 })
+      await expect(liquid.parseAndRender('{% layout none %}ok')).resolves.toBe('ok')
+    })
+
+    it('should default maxDepth to 128', async () => {
+      const liquid = new Liquid({ templates: chain(128, 'include') })
+      await expect(liquid.parseAndRender('{% include "t0" %}')).resolves.toBe('done')
+      const overflow = new Liquid({ templates: chain(129, 'include') })
+      await expect(overflow.parseAndRender('{% include "t0" %}')).rejects.toThrow('template depth limit exceeded')
+    })
+
+    it('should enforce maxDepth in sync render', () => {
+      const liquid = new Liquid({ templates: chain(3, 'include'), maxDepth: 2 })
+      expect(() => liquid.parseAndRenderSync('{% include "t0" %}')).toThrow('template depth limit exceeded')
+    })
+  })
+
   describe('strip_html ReDoS', () => {
     // Regression for O(n^2) backtracking on unclosed `<script` / `<style` openers.
     // The previous regex stalled the event loop for ~10s on 350KB of `'<script'.repeat`.
@@ -145,11 +180,13 @@ describe('DoS related', function () {
       const payload = '<script'.repeat(50000)
       expect(liquid.parseAndRenderSync('{{ x | strip_html }}', { x: payload })).toBe(payload)
     }, 1000)
+
     it('should handle many unclosed <style openers in linear time', () => {
       const liquid = new Liquid()
       const payload = '<style'.repeat(50000)
       expect(liquid.parseAndRenderSync('{{ x | strip_html }}', { x: payload })).toBe(payload)
     }, 1000)
+
     it('should handle <script openers that have > but no </script> in linear time', () => {
       const liquid = new Liquid()
       const payload = '<script>foo'.repeat(50000)

test/integration/tags/for.spec.ts

@@ -120,6 +120,18 @@ describe('tags/for', function () {
       const html = await liquid.parseAndRender(src, scope)
       return expect(html).toBe('b')
     })
+
+    it('should goto else when limit empties collection', async function () {
+      const src = '{%for c in alpha limit:0%}a{%else%}b{%endfor%}'
+      const html = await liquid.parseAndRender(src, scope)
+      return expect(html).toBe('b')
+    })
+
+    it('should goto else when offset past end', async function () {
+      const src = '{%for c in alpha offset:10%}a{%else%}b{%endfor%}'
+      const html = await liquid.parseAndRender(src, scope)
+      return expect(html).toBe('b')
+    })
   })
 
   it('should support for with forloop', async function () {