Conditionally Providing Layers in an Application

const ProductionEmailProviderServiceLayer; // Layer<EmailProviderService, never, EnvService>

const DevEmailProviderServiceLayer; // Layer<EmailProviderService, never, EnvService>

const EmailProviderServiceLayer = Layer.effect(
  EmailProviderService,
  Effect.gen(function* (_) {
    const env = yield* _(EnvService);

    if (env.ENVIRONMENT === "development") {
      return yield* _(DevEmailProviderServiceLayer);
    }

    return yield* _(ProductionEmailProviderServiceLayer);
  }),
);

const ProductionEmailProviderServiceLayer; // Layer<EmailProviderService, never, EnvService>

const DevEmailProviderServiceLayer; // Layer<EmailProviderService, never, EnvService>

const EmailProviderServiceLayer = Layer.effect(
  EmailProviderService,
  Effect.gen(function* (_) {
    const env = yield* _(EnvService);

    if (env.ENVIRONMENT === "development") {
      return yield* _(DevEmailProviderServiceLayer);
    }

    return yield* _(ProductionEmailProviderServiceLayer);
  }),
);