fix(context): use null-prototype scope and register objects

Add createScope(); use for bottom scope, spawn default, getAll merge, ctx.push frames, filter loops, include/layout blocks registers, and cycle groups. registers uses Object.create(null) and getRegister uses ??.

For-loop continue register defaults to 0 (not {}): Array.slice coerces plain {} but not null-prototype objects.

Export createScope from the package entry.

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

src/context/context.spec.ts

@@ -216,4 +216,12 @@ describe('Context', function () {
       expect(ctx.getSync(['foo'])).toEqual('zoo')
     })
   })
+  describe('scope storage', function () {
+    it('should use null prototype for bottom scope', function () {
+      expect(Object.getPrototypeOf(new Context().bottom())).toBeNull()
+    })
+    it('should use null prototype for getAll() merge result', function () {
+      expect(Object.getPrototypeOf(new Context({ a: 1 }).getAll())).toBeNull()
+    })
+  })
 })

src/context/context.ts

@@ -2,7 +2,7 @@ import { getPerformance } from '../util/performance'
 import { Drop } from '../drop/drop'
 import { __assign } from 'tslib'
 import { NormalizedFullOptions, defaultOptions, RenderOptions } from '../liquid-options'
-import { Scope } from './scope'
+import { Scope, createScope } from './scope'
 import { hasOwnProperty, isArray, isNil, isUndefined, isString, isFunction, toLiquid, InternalUndefinedVariableError, toValueSync, isObject, Limiter, toValue } from '../util'
 
 type PropertyKey = string | number;
@@ -12,8 +12,8 @@ export class Context {
    * insert a Context-level empty scope,
    * for tags like `{% capture %}` `{% assign %}` to operate
    */
-  private scopes: Scope[] = [{}]
-  private registers = {}
+  private scopes: Scope[] = [createScope()]
+  private registers: Record<string, any> = Object.create(null)
   /**
    * user passed in scope
    * `{% increment %}`, `{% decrement %}` changes this scope,
@@ -49,7 +49,7 @@ export class Context {
     this.renderLimit = renderLimit ?? new Limiter('template render', getPerformance().now() + (renderOptions.renderLimit ?? opts.renderLimit))
   }
   public getRegister<T> (key: string, defaultValue: T = undefined as T): T {
-    return (this.registers[key] = this.registers[key] || defaultValue)
+    return (this.registers[key] = this.registers[key] ?? defaultValue)
   }
   public setRegister (key: string, value: any) {
     return (this.registers[key] = value)
@@ -62,7 +62,7 @@ export class Context {
   }
   public getAll () {
     return [this.globals, this.environments, ...this.scopes]
-      .reduce((ctx, val) => __assign(ctx, val), {})
+      .reduce((ctx, val) => __assign(ctx, val), createScope())
   }
   /**
    * @deprecated use `_get()` or `getSync()` instead
@@ -102,7 +102,7 @@ export class Context {
   public bottom () {
     return this.scopes[0]
   }
-  public spawn (scope = {}) {
+  public spawn (scope: object = createScope()) {
     return new Context(scope, this.opts, {
       sync: this.sync,
       globals: this.globals,

src/context/scope.ts

@@ -5,3 +5,13 @@ interface ScopeObject extends Record<string | number | symbol, any> {
 }
 
 export type Scope = ScopeObject | Drop
+
+/**
+ * Plain scope bag with a null prototype so lookups like `__proto__` are not the
+ * Object.prototype accessor unless explicitly assigned as an own property.
+ */
+export function createScope (props?: Record<PropertyKey, any>): ScopeObject {
+  return props == null
+    ? Object.create(null)
+    : Object.assign(Object.create(null), props)
+}