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ErrorsNEXUS_LEGACY_DECORATORS

This page documents the 0.4 release candidates of @nexusdi/core. The newest on npm is 0.4.0-rc.1. The documentation for 0.3.2, the current release, is at nexus.js.org. Try the release candidate.

NEXUS_LEGACY_DECORATORS

Every decorator that @nexusdi/decorators exports throws NEXUS_LEGACY_DECORATORS when TypeScript calls it as a legacy decorator, which it does when tsconfig.json sets experimentalDecorators. @Injectable and @Module fail on a class, and @Inject fails on an accessor. The decorators are standard (TC39) decorators, and each one checks the arguments it receives before it records anything. The check runs when the decorator is applied, so the error ends the import of the module that declares the class. It is thrown bare, because no container exists yet, and NEXUS_BLUEPRINT_INVALID never wraps it. @UseInterceptors from @nexusdi/interceptors reports the same flag as NEXUS_INTERCEPTOR_INVALID with the reason legacy-decorators.

Reproduce NEXUS_LEGACY_DECORATORS

@Injectable throws NEXUS_LEGACY_DECORATORS when it receives the class alone, the call TypeScript emits for a class decorator under experimentalDecorators. The region makes that call by hand, so it runs under any compiler setting. @nexusdi/decorators writes this message itself, so it carries its full text and fix line with no text pack and no errors() plugin.

import { Token, isNexusError } from '@nexusdi/core';
import { Injectable } from '@nexusdi/decorators';
 
interface IReactorCore {
  readonly output: number;
}
const REACTOR = new Token<IReactorCore>('ReactorCore');
 
class QuantumComputer {
  constructor(readonly reactor: IReactorCore) {}
}
 
// Under experimentalDecorators, TypeScript calls a class decorator with the
// class alone. This line makes the same call by hand.
const legacyCall = Injectable({ deps: [REACTOR] }) as unknown as (
  target: unknown,
) => void;
 
let code = '';
let message = '';
try {
  legacyCall(QuantumComputer);
} catch (error) {
  if (!isNexusError(error, 'NEXUS_LEGACY_DECORATORS')) throw error;
  code = error.code;
  message = error.message;
}
const thrown = code; // -> 'NEXUS_LEGACY_DECORATORS'
console.log(thrown);
const lines = message.split('\n'); // -> ["[NEXUS_LEGACY_DECORATORS] @Injectable was called as a legacy decorator, and NexusDI's decorators are standard (TC39) decorators.", '  Fix: remove experimentalDecorators from tsconfig, or register the class with provide() and defineModule().']
console.log(lines.join('\n'));

Try it: run npm install @nexusdi/core@next @nexusdi/decorators@next, save the region as legacy.ts and run npx tsx legacy.ts. It prints the code, NEXUS_LEGACY_DECORATORS, then the two-line message: [NEXUS_LEGACY_DECORATORS] @Injectable was called as a legacy decorator, and NexusDI's decorators are standard (TC39) decorators. and its Fix: line.

The second region declares a class with a real @Injectable:

import { Nexus, Token, provide } from '@nexusdi/core';
import { Injectable } from '@nexusdi/decorators';
 
interface IReactorCore {
  readonly output: number;
}
interface IShipComputer {
  readonly reactor: IReactorCore;
}
const REACTOR = new Token<IReactorCore>('ReactorCore');
const COMPUTER = new Token<IShipComputer>('ShipComputer');
 
class FusionReactor implements IReactorCore {
  readonly output = 1.21;
}
 
@Injectable({ deps: [REACTOR] })
class QuantumComputer implements IShipComputer {
  constructor(readonly reactor: IReactorCore) {}
}
 
await using ship = await Nexus.create([
  provide(REACTOR, { useClass: FusionReactor }),
  provide(COMPUTER, { useClass: QuantumComputer }),
]);
const output = ship.get(COMPUTER).reactor.output; // -> 1.21
console.log(output);

Try it: save the region as decorated.ts and run npx tsx decorated.ts with the tsconfig.json from Getting Started. It prints 1.21. Add the flag to the compilerOptions:

Not run

{
  "compilerOptions": {
    "target": "es2022",
    "module": "nodenext",
    "strict": true,
    "noEmit": true,
    "lib": ["es2022"],
    "types": ["node"],
    "experimentalDecorators": true
  }
}

npx tsc now reports TS1238 on the @Injectable line, and says the runtime will invoke the decorator with 1 arguments where it expects 2. npx tsx decorated.ts throws an uncaught LegacyDecoratorsError and prints a stack trace headed LegacyDecoratorsError: [NEXUS_LEGACY_DECORATORS] @Injectable was called as a legacy decorator, with no 1.21. Remove the flag and the program prints 1.21 again.

Fix NEXUS_LEGACY_DECORATORS

NEXUS_LEGACY_DECORATORS has two fixes. Remove experimentalDecorators from tsconfig.json, so TypeScript compiles every decorator as a standard decorator, as the last step above shows. When the project keeps the flag for another library, declare the class without decorators: static deps on the class and provide() in the list passed to Nexus.create, or in a module, work under every compiler setting.

import { Nexus, Token, provide } from '@nexusdi/core';
 
interface IReactorCore {
  readonly output: number;
}
interface IShipComputer {
  readonly reactor: IReactorCore;
}
const REACTOR = new Token<IReactorCore>('ReactorCore');
const COMPUTER = new Token<IShipComputer>('ShipComputer');
 
class FusionReactor implements IReactorCore {
  readonly output = 1.21;
}
class QuantumComputer implements IShipComputer {
  static deps = [REACTOR] as const;
  constructor(readonly reactor: IReactorCore) {}
}
 
await using ship = await Nexus.create([
  provide(REACTOR, { useClass: FusionReactor }),
  provide(COMPUTER, { useClass: QuantumComputer }),
]);
const output = ship.get(COMPUTER).reactor.output; // -> 1.21
console.log(output);

Try it: save the region as fixed.ts, set "experimentalDecorators": true in tsconfig.json and run npx tsx fixed.ts. npx tsc reports nothing, and the program prints 1.21. Using NexusDI with experimentalDecorators covers the second fix in full.

Fields of LegacyDecoratorsError

  • code: 'NEXUS_LEGACY_DECORATORS'.
  • decorator: the name of the decorator that received the legacy call, without the @, such as 'Injectable' for @Injectable.
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