Basic Setup

import { createContainer, createToken } from '@vielzeug/wireit';

const Logger = createToken<{ log(message: string): void }>('Logger');
const Service = createToken<{ run(): Promise<void> }>('Service');

const container = createContainer();

container.value(Logger, {
  log(message) {
    console.log(message);
  },
});

container.factory(
  Service,
  (logger) => {
    return {
      async run() {
        logger.log('running');
      },
    };
  },
  {
    deps: [Logger],
  },
);

await container.resolve(Service);

Use resolveOptional() when a provider is truly optional.