Function discover

packages/angular/cli/src/package-managers/discovery.ts:92–131

(
  host: Host,
  startDir: string,
  logger?: Logger,
)

 * @returns A promise that resolves to the name of the discovered package manager, or null if none is found.
 */
export async function discover(
  host: Host,
  startDir: string,
  logger?: Logger,
): Promise<PackageManagerName | null> {
  logger?.debug(`Starting package manager discovery in '${startDir}'...`);
  let currentDir = startDir;

  while (true) {
    const found = await findLockfiles(host, currentDir, logger);

    if (found.size > 0) {
      logger?.debug(`Found lockfile(s): [${[...found].join(', ')}]. Applying precedence...`);
      for (const packageManager of PACKAGE_MANAGER_PRECEDENCE) {
        if (found.has(packageManager)) {
          logger?.debug(`Selected '${packageManager}' based on precedence.`);

          return packageManager;
        }
      }
    }

    // Stop searching if we reach the git repository root.
    if (await isDirectory(host, join(currentDir, '.git'))) {
      logger?.debug(`Reached repository root at '${currentDir}'. Stopping search.`);

      return null;
    }

    const parentDir = dirname(currentDir);
    if (parentDir === currentDir) {
      // We have reached the filesystem root.
      logger?.debug('Reached filesystem root. No lockfile found.');

      return null;
    }

    currentDir = parentDir;
  }
}