fix: nested block for layout (#883)

src/context/context.ts

@@ -48,8 +48,8 @@ export class Context {
     this.memoryLimit = memoryLimit ?? new Limiter('memory alloc', renderOptions.memoryLimit ?? opts.memoryLimit)
     this.renderLimit = renderLimit ?? new Limiter('template render', getPerformance().now() + (renderOptions.renderLimit ?? opts.renderLimit))
   }
-  public getRegister (key: string) {
-    return (this.registers[key] = this.registers[key] || {})
+  public getRegister<T> (key: string, defaultValue: T = undefined as T): T {
+    return (this.registers[key] = this.registers[key] || defaultValue)
   }
   public setRegister (key: string, value: any) {
     return (this.registers[key] = value)

src/tags/block.ts

@@ -23,20 +23,25 @@ export default class extends Tag {
   * render (ctx: Context, emitter: Emitter) {
     const blockRender = this.getBlockRender(ctx)
     if (ctx.getRegister('blockMode') === BlockMode.STORE) {
-      ctx.getRegister('blocks')[this.block] = blockRender
+      ctx.getRegister('blocks', {} as Record<string, any>)[this.block] = blockRender
     } else {
       yield blockRender(new BlockDrop(), emitter)
     }
   }
 
   private getBlockRender (ctx: Context) {
+    const self = this as Tag
     const { liquid, templates } = this
-    const renderChild = ctx.getRegister('blocks')[this.block]
+    const renderChild = ctx.getRegister('blocks', {} as Record<string, any>)[this.block]
     const renderCurrent = function * (superBlock: BlockDrop, emitter: Emitter) {
-      // add {{ block.super }} support when rendering
+      const stack: Tag[] = ctx.getRegister('blockStack', [])
+      if (stack.includes(self)) throw new Error('block tag cannot be nested')
+
+      stack.push(self)
       ctx.push({ block: superBlock })
       yield liquid.renderer.renderTemplates(templates, ctx, emitter)
       ctx.pop()
+      stack.pop()
     }
     return renderChild
       ? (superBlock: BlockDrop, emitter: Emitter) => renderChild(

src/tags/cycle.ts

@@ -27,7 +27,7 @@ export default class extends Tag {
   * render (ctx: Context, emitter: Emitter): Generator<unknown, unknown, unknown> {
     const group = (yield evalToken(this.group, ctx)) as ValueToken
     const fingerprint = `cycle:${group}:` + this.candidates.join(',')
-    const groups = ctx.getRegister('cycle')
+    const groups = ctx.getRegister('cycle', {} as Record<string, number>)
     let idx = groups[fingerprint]
 
     if (idx === undefined) {

src/tags/for.ts

@@ -50,7 +50,7 @@ export default class extends Tag {
     }
 
     const continueKey = 'continue-' + this.variable + '-' + this.collection.getText()
-    ctx.push({ continue: ctx.getRegister(continueKey) })
+    ctx.push({ continue: ctx.getRegister(continueKey, {}) })
     const hash = yield this.hash.render(ctx)
     ctx.pop()
 

src/tags/layout.ts

@@ -32,7 +32,7 @@ export default class extends Tag {
     // render remaining contents and store rendered results
     ctx.setRegister('blockMode', BlockMode.STORE)
     const html = yield renderer.renderTemplates(this.templates, ctx)
-    const blocks = ctx.getRegister('blocks')
+    const blocks = ctx.getRegister('blocks', {} as Record<string, any>)
 
     // set whole content to anonymous block if anonymous doesn't specified
     if (blocks[''] === undefined) blocks[''] = (parent: BlankDrop, emitter: Emitter) => emitter.write(html)