Function build

packages/backends/src/index.ts:73–415

}

export const build: BuildV2 = async args => {
  // Reject `module:function` colon syntax in entrypoints. fs-detectors
  // parses it into `Service.handlerFunction` regardless of service
  // type.
  if (typeof args.config?.handlerFunction === 'string') {
    throw new Error(
      `Named-function entrypoints are not supported for JavaScript services (got "${args.entrypoint}:${args.config.handlerFunction}"). Put each handler in its own file with a default export.`
    );
  }

  const downloadResult = await downloadInstallAndBundle(args);
  const nodeVersion = await getNodeVersion(
    args.workPath,
    undefined,
    args.config,
    args.meta
  );
  const isBun = isBunVersion(nodeVersion);
  const builderName = '@vercel/backends';

  const span =
    args.span ??
    new Span({
      name: builderName,
    });

  span.setAttributes({
    'builder.name': builderName,
  });

  const buildSpan = span.child('vc.builder.backends.build');

  return buildSpan.trace(async () => {
    const entrypoint = await findEntrypointWithHintOrThrow(
      args.workPath,
      args.entrypoint
    );
    debug('Entrypoint', entrypoint);
    args.entrypoint = entrypoint;

    const serviceName =
      typeof args.config?.serviceName === 'string' &&
      args.config.serviceName !== ''
        ? args.config.serviceName
        : undefined;

    // Edge Runtime is not supported in services. Without this check the Node
    // service builder silently ignores an in-file
    // `export const config = { runtime: 'edge' }` and ships a Node lambda;
    // surface it as a clear build error instead.
    if (serviceName) {
      const staticConfig = getConfig(
        new Project(),
        join(args.workPath, entrypoint)
      );
      const configuredRuntime = staticConfig?.runtime;
      if (
        typeof configuredRuntime === 'string' &&