Function installItem

packages/cli/src/registry/installer.ts:69–94

(
  item: RegistryItem,
  options: InstallOptions,
)

 * parallel and writing it to its validated target path.
 */
export async function installItem(
  item: RegistryItem,
  options: InstallOptions,
): Promise<InstallResult> {
  const baseUrl = options.baseUrl ?? DEFAULT_REGISTRY_URL;
  const destDir = resolve(options.destDir);

  // Validate all targets up-front so a malformed item fails before any write.
  for (const file of item.files) {
    assertSafeTarget(destDir, file.target);
  }

  const written = await Promise.all(
    item.files.map(async (file: FileTarget) => {
      const destPath = resolve(destDir, file.target);
      await fetchItemFile(item, file, destPath, baseUrl);
      if (isInstalledRegistryBlockComposition(item, file)) {
        const source = readFileSync(destPath, "utf-8");
        writeFileSync(destPath, addRegistryItemMarker(source, item), "utf-8");
      }
      return destPath;
    }),
  );

  return { written };
}