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Oxc linker rejects parenthesized resolveMetadata return in deferred class metadata

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
angular, typescript
Domain
build-system, tooling

Research direction

Run the minimal reproduction with npm run build and compare it with npm run build:babel. Start at OxcAstHost.parseReturnValue() and PartialClassMetadataAsyncLinkerVersion1.linkPartialDeclaration, using fixture/index.mjs to compare the parenthesized concise arrow body with the working block-body form. Done means both equivalent callback forms link successfully with the default Oxc linker.

Written by the indexing model from the issue text.

Description

area: @angular/build gemini-triaged
Command

build

Description

With @angular/build@22.2.0-rc.0, the default Oxc linker fails to process a partial ɵɵngDeclareClassMetadataAsync declaration whose resolveMetadata callback returns a parenthesized object literal. The same input builds successfully with NG_BUILD_BABEL_LINKER=1.

The fixture below is hand-reduced from Angular 22.1.7 output for a library component containing @defer; it removes the original application's dependencies and UI. It exercises the real ng build pipeline, not a mock linker.

Is this a regression?

The original library artifact passes our stable Angular 20/21/22 CI matrix and fails the 22.2.0-rc.0 canary. I have not bisected the first affected version using this reduced reproduction.

Minimal Reproduction

Create an empty directory with the following files, then run:

npm install
npm run build
# Fails: Unsupported syntax, expected an object literal.

npm run build:babel
# Succeeds: same input, Babel linker.

The build cache is disabled in this reproduction.

Complete minimal project files

package.json

{
  "name": "angular-oxc-deferred-metadata-repro",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "scripts": {
    "build": "ng build",
    "build:babel": "NG_BUILD_BABEL_LINKER=1 ng build"
  },
  "dependencies": {
    "@angular/core": "22.2.0-rc.0",
    "@angular/common": "22.2.0-rc.0",
    "@angular/compiler": "22.2.0-rc.0",
    "@angular/platform-browser": "22.2.0-rc.0",
    "rxjs": "7.8.2",
    "tslib": "2.8.1",
    "deferred-metadata-fixture": "file:./fixture"
  },
  "devDependencies": {
    "@angular/build": "22.2.0-rc.0",
    "@angular/cli": "22.2.0-rc.0",
    "@angular/compiler-cli": "22.2.0-rc.0",
    "typescript": "6.0.3"
  }
}

angular.json

{
  "version": 1,
  "cli": {
    "cache": {
      "enabled": false
    },
    "analytics": false
  },
  "projects": {
    "repro": {
      "projectType": "application",
      "root": "",
      "architect": {
        "build": {
          "builder": "@angular/build:application",
          "options": {
            "browser": "src/main.ts",
            "tsConfig": "tsconfig.json",
            "index": "src/index.html",
            "outputPath": "dist",
            "optimization": false
          }
        }
      }
    }
  }
}

tsconfig.json

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "preserve",
    "moduleResolution": "bundler",
    "experimentalDecorators": true,
    "skipLibCheck": true,
    "strict": true,
    "lib": [
      "ES2022",
      "DOM"
    ]
  },
  "files": [
    "src/main.ts"
  ]
}

src/main.ts

import { Component } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';
import { DeferredFixture } from 'deferred-metadata-fixture';

@Component({ selector: 'app-root', template: 'Linker reproduction' })
class App {
  constructor() { console.log(DeferredFixture); }
}

bootstrapApplication(App).catch(console.error);

src/index.html

<!doctype html><html><head><title>Reproduction</title><base href="/"></head><body><app-root></app-root></body></html>

fixture/package.json

{
  "name": "deferred-metadata-fixture",
  "version": "1.0.0",
  "type": "module",
  "main": "index.mjs",
  "types": "index.d.ts"
}

fixture/index.mjs

import * as i0 from '@angular/core';

export class DeferredFixture {}

// Reduced from Angular 22.1.7 output for a component containing @defer.
// The parenthesized object returned by resolveMetadata triggers the failure.
i0.ɵɵngDeclareClassMetadataAsync({
  minVersion: '18.0.0',
  version: '22.1.7',
  ngImport: i0,
  type: DeferredFixture,
  resolveDeferredDeps: () => [],
  resolveMetadata: () => ({
    decorators: [],
    ctorParameters: null,
    propDecorators: null,
  }),
});

fixture/index.d.ts

export declare class DeferredFixture {}

Additional control: in fixture/index.mjs, replace resolveMetadata: () => ({ ... }) with the equivalent resolveMetadata: () => { return { ... }; }. Running npm run build then succeeds with the default Oxc linker. This was verified locally, in addition to the Babel comparison.

Expected: both equivalent callback forms link successfully with the default builder.

Actual: only the parenthesized expression form fails.

Exception or Error
Unsupported syntax, expected an object literal. [plugin angular-compiler]

at OxcAstHost.parseObjectLiteral (.../oxc-ast-host.js:95:19)
at _AstObject.parse
at _AstValue.getObject
at PartialClassMetadataAsyncLinkerVersion1.linkPartialDeclaration
at FileLinker.linkPartialDeclaration
at OxcLinker.linkCallExpression
Your Environment
Angular CLI: 22.2.0-rc.0
Angular: 22.2.0-rc.0
@angular/build: 22.2.0-rc.0
@angular/compiler-cli: 22.2.0-rc.0
TypeScript: 6.0.3
Node.js: 26.5.0
npm: 11.17.0
OS: darwin arm64

The original failure also occurs on Ubuntu CI with Node 24.17.0.

Anything else relevant?

The parser represents the concise arrow body as ParenthesizedExpression(ObjectExpression). OxcAstHost.parseReturnValue() returns the body unchanged; the subsequent object-literal check only accepts ObjectExpression. Unwrapping the parenthesized return expression before interpreting the metadata appears to be the required fix.

Related PR #33769 addresses parentheses when emitting JavaScript, whereas this failure occurs when reading the callback's return value.

Dominant language
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