Skip to Content
ErrorsNEXUS_MISSING_DEPS

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_MISSING_DEPS

NEXUS_MISSING_DEPS means a class whose constructor takes parameters is bound with no deps from either the class or the binding. NexusDI has no type information to read at run time, so the class has to say what to pass. Nexus.create reports it inside NEXUS_BLUEPRINT_INVALID.

Reproduce NEXUS_MISSING_DEPS

The region binds SurveyDrone to ScoutDrone, whose constructor takes the ship computer and declares no deps. Without a plugin, core prints a one-line message that starts with the code and ends with the address of this page. With errors() from @nexusdi/errors registered (npm install @nexusdi/errors@next), the same error carries the full text and its fix.

import { Nexus, Token, defineModule, isNexusError } from '@nexusdi/core';
import { provide } from '@nexusdi/core';
import { errors } from '@nexusdi/errors';
 
interface IShipComputer {
  status(): string;
}
interface ISurveyDrone {
  scan(): string;
}
const COMPUTER = new Token<IShipComputer>('ShipComputer');
const DRONE = new Token<ISurveyDrone>('SurveyDrone');
 
class QuantumComputer implements IShipComputer {
  status() {
    return 'online';
  }
}
class ScoutDrone implements ISurveyDrone {
  constructor(private readonly computer: IShipComputer) {}
  scan() {
    return `scan with computer ${this.computer.status()}`;
  }
}
 
const Tactical = defineModule({
  name: 'Tactical',
  providers: [
    provide(COMPUTER, { useClass: QuantumComputer }),
    provide(DRONE, { useClass: ScoutDrone, lifetime: 'transient' }),
  ],
});
 
const thin = await Nexus.create(Tactical).catch((error: unknown) => error);
if (!isNexusError(thin, 'NEXUS_BLUEPRINT_INVALID')) throw thin;
const line = thin.errors[0]?.message; // -> '[NEXUS_MISSING_DEPS] token=SurveyDrone module=Tactical arity=1 useClass=ScoutDrone. https://nexus.js.org/errors/NEXUS_MISSING_DEPS'
console.log(line);
 
const full = await Nexus.create(Tactical, { plugins: [errors()] }).catch(
  (error: unknown) => error,
);
if (!isNexusError(full, 'NEXUS_BLUEPRINT_INVALID')) throw full;
const text = full.errors[0]?.message.split('\n'); // -> ['[NEXUS_MISSING_DEPS] ScoutDrone (useClass for SurveyDrone) in Tactical takes 1 constructor parameter and has no deps.', '  Fix: add deps to the binding, declare static deps = [...] as const on ScoutDrone, or decorate it with @Injectable({ deps }).']
console.log(text);

Try it: save the region as error.ts and run npx tsx error.ts. It prints the one-line message, then the full text as an array of two lines. The arity field is the number of constructor parameters the compiler counted. Then save the fix region below as fixed.ts and run npx tsx fixed.ts. It prints scan with computer online.

Fix NEXUS_MISSING_DEPS

NEXUS_MISSING_DEPS is fixed by declaring the deps. Write static deps = [COMPUTER] as const on the class, or deps: [COMPUTER] on the binding for a class you cannot edit. A class listed bare in providers can also use @Injectable({ deps }) from @nexusdi/decorators. The compiler reads constructor.length, which counts the parameters before the first default or rest parameter, so a class whose parameters all have defaults builds with no deps.

import { Nexus, Token, defineModule, provide } from '@nexusdi/core';
 
interface IShipComputer {
  status(): string;
}
interface ISurveyDrone {
  scan(): string;
}
const COMPUTER = new Token<IShipComputer>('ShipComputer');
const DRONE = new Token<ISurveyDrone>('SurveyDrone');
 
class QuantumComputer implements IShipComputer {
  status() {
    return 'online';
  }
}
class ScoutDrone implements ISurveyDrone {
  static deps = [COMPUTER] as const;
  constructor(private readonly computer: IShipComputer) {}
  scan() {
    return `scan with computer ${this.computer.status()}`;
  }
}
 
const Tactical = defineModule({
  name: 'Tactical',
  providers: [
    provide(COMPUTER, { useClass: QuantumComputer }),
    provide(DRONE, { useClass: ScoutDrone, lifetime: 'transient' }),
  ],
});
 
await using ship = await Nexus.create(Tactical);
const scan = ship.get(DRONE).scan(); // -> 'scan with computer online'
console.log(scan);

Try it: delete the static deps = [COMPUTER] as const; line from ScoutDrone in fixed.ts and run it again. tsc reports nothing, because the type checker cannot see the missing list. Nexus.create rejects with a BlueprintError whose message lists [NEXUS_MISSING_DEPS] token=SurveyDrone module=Tactical arity=1 useClass=ScoutDrone. Put the line back and the program prints scan with computer online again.

Fields of MissingDepsError

MissingDepsError carries these fields:

  • token: the display name of the token the class is bound to.
  • module: the module of the binding.
  • arity: the number of constructor parameters, read from constructor.length.
  • useClass: the class a useClass binding names, or null when the class is its own token.
  • bare: true for a class listed bare in providers, which reads @Injectable.
ErrorsRegister a plugin