mergePackageRootsForDirs function

Map<String, String> mergePackageRootsForDirs(Iterable<String> packageDirs)

Merges the package roots resolved from each given package directory's .dart_tool/package_config.json into a single name→root map.

This is what lets one packages.sum bundle cover the union of several dependency closures — e.g. an editor's deps and a UI package whose widgets a code-typed field references — without the editor having to depend on that package directly (the bundle is loaded at runtime, never compiled against). On a name collision the later directory wins; within one workspace these are path deps resolving to the same root, so collisions are benign.

Throws SummaryConfigException if any directory lacks a resolved config.

Implementation

Map<String, String> mergePackageRootsForDirs(Iterable<String> packageDirs) {
  final merged = <String, String>{};
  for (final dir in packageDirs) {
    final configFile =
        io.File(p.join(dir, '.dart_tool', 'package_config.json'));
    if (!configFile.existsSync()) {
      throw SummaryConfigException(
          '${configFile.path} not found — run `flutter pub get` / '
          '`dart pub get` in $dir first.');
    }
    merged.addAll(readPackageRoots(configFile));
  }
  return merged;
}