Method _start

packages/cli/src/util/dev/server.ts:1003–1268

* Launches the `vercel dev` server.

(...listenSpec: ListenSpec)

   * Launches the `vercel dev` server.
   */
  async _start(...listenSpec: ListenSpec): Promise<void> {
    if (!fs.existsSync(this.cwd)) {
      throw new Error(`${chalk.bold(this.cwd)} doesn't exist`);
    }

    if (!fs.lstatSync(this.cwd).isDirectory()) {
      throw new Error(`${chalk.bold(this.cwd)} is not a directory`);
    }

    const { ig } = await getVercelIgnore(this.cwd);
    this.filter = ig.createFilter();

    let address: string | null = null;
    while (typeof address !== 'string') {
      try {
        address = (await listen(this.server, ...listenSpec)).toString();
      } catch (err: unknown) {
        if (isErrnoException(err)) {
          output.debug(`Got listen error: ${err.code}`);
          if (err.code === 'EADDRINUSE') {
            if (typeof listenSpec[0] === 'number') {
              // Increase port and try again
              output.note(
                `Requested port ${chalk.yellow(
                  String(listenSpec[0])
                )} is already in use`
              );
              listenSpec[0]++;
            } else {
              output.error(
                `Requested socket ${chalk.cyan(
                  listenSpec[0]
                )} is already in use`
              );
              process.exit(1);
            }
          }
        } else {
          throw err;
        }
      }
    }

    this._address = new URL(replaceLocalhost(address));

    const vercelConfig = await this.getVercelConfig();

    let devCommandPromise: Promise<void> | undefined;
    if (this.shouldUseServicesOrchestrator()) {
      this.orchestrator = new ServicesOrchestrator({
        services: this.services || [],
        cwd: this.cwd,
        repoRoot: this.repoRoot,
        env: this.envConfigs.allEnv,
        proxyOrigin: this.address.origin,
        useImplicitEnvInjection: this.useImplicitServicesEnvInjection,
      });
      devCommandPromise = this.orchestrator.startAll();