Function build

packages/python/src/index.ts:483–1323

({
  workPath,
  repoRootPath,
  files: originalFiles,
  entrypoint: rawEntrypoint,
  meta = {},
  config,
  span: parentSpan,
  service,
  registerPreDeploy,
})

}

export const build: BuildVX = async ({
  workPath,
  repoRootPath,
  files: originalFiles,
  entrypoint: rawEntrypoint,
  meta = {},
  config,
  span: parentSpan,
  service,
  registerPreDeploy,
}) => {
  let entrypoint: string | undefined =
    rawEntrypoint === '<detect>' ? undefined : rawEntrypoint;

  const builderSpan = parentSpan ?? new Span({ name: 'vc.builder' });
  const framework = config?.framework;
  let shouldInstallVercelWorkers = config?.hasWorkerServices === true;
  let subscribers: Subscriber[] = [];
  let spawnEnv: NodeJS.ProcessEnv | undefined;
  // Custom install command from dashboard/project settings, if any.
  let projectInstallCommand: string | undefined;
  // Track whether a custom install command was used. When true, runtime
  // dependency installation is disabled because custom install commands may
  // install dependencies not tracked in uv.lock.
  let hasCustomCommand = false;
  // Track whether a custom build command/script was used. When true, compileall
  // is disabled (a custom build may emit its own bytecode or bypass the venv
  // layout compileall assumes). It does not affect runtime installation, since
  // dependencies are still installed normally.
  let hasCustomBuildCommand = false;

  const target = getTargetPlatform(meta.isDev ?? false);

  debug(`workPath: ${workPath}`);

  workPath = await downloadFilesInWorkPath({
    workPath,
    files: originalFiles,
    entrypoint,
    meta,
  });

  // `tool.vercel.subscribers` declares background workers for a standalone
  // Python app and compiles them into additional queue-triggered Lambdas.
  // It is intentionally scoped to non-service framework builds:
  //   - `experimentalServices` projects already declare queue consumers as
  //     first-class `worker`/`job` services, so a second implicit mechanism
  //     would be redundant and ambiguous (services can share one pyproject.toml,
  //     which would duplicate every subscriber across each service build).
  //   - Bare `api/**` functions build once per file sharing this workPath, so
  //     emitting subscribers there would duplicate their outputs per build.
  if (!service && isPythonFramework(framework)) {
    subscribers = await getPyprojectSubscribers(workPath);
    shouldInstallVercelWorkers ||= subscribers.length > 0;
  }

  try {
    // See: https://stackoverflow.com/a/44728772/376773