packageRootFromFileUriString function

Future<String> packageRootFromFileUriString(String fileUriString, { DartToolingDaemon? dtd, @visibleForTesting bool throwOnDtdSearchFailed = false, })

Attempts to detect the package root of fileUriString, which is expected to be a proper file URI (i.e. starts with "file://").

This method first tries to use the Dart Tooling Daemon to walk the directory structure of fileUriString and look for the package root; we consider a directory to be a package root if it contains the .dart_tool directory.

If we cannot find the package root using the Dart Tooling Daemon, we use the heuristic that a Dart executable within a Dart package should reside in one of the following top-level folders:

• lib
• bin
• integration_test
• test
• benchmark
• example

The URI returned will be a file URI String and will NOT have a trailing slash.

Implementation

Future<String> packageRootFromFileUriString(
  String fileUriString, {
  DartToolingDaemon? dtd,
  @visibleForTesting bool throwOnDtdSearchFailed = false,
}) async {
  assert(
    fileUriString.startsWith(_fileUriPrefix),
    'Invalid URI format: expected URI String to start with "$_fileUriPrefix".',
  );

  if (dtd != null) {
    // Use type [Object] so we can store exceptions of all types.
    Object? exception;

    var uri = Uri.parse(fileUriString);
    while (uri.pathSegments.length > 1) {
      // Remove the last path segment.
      uri = uri.replace(
        pathSegments: uri.pathSegments.sublist(0, uri.pathSegments.length - 1),
      );
      try {
        final directoryContents = await dtd.listDirectoryContents(uri);
        final containsDartToolDirectory = (directoryContents.uris ?? const [])
            .any((uri) => uri.path.endsWith('.dart_tool/'));
        if (containsDartToolDirectory) {
          final uriAsString = uri.toString();
          return _assertUriFormatAndReturn(
            uriAsString.endsWith('/')
                ? uriAsString.substring(0, uriAsString.length - 1)
                : uriAsString,
          );
        }
      } catch (e) {
        // Fail gracefully on exception, and proceed to using heuristic below.
        exception = e;
        break;
      }
    }
    if (throwOnDtdSearchFailed) {
      throw Exception('Expected DTD to detect the package root, but it failed'
          '${exception != null ? ' with exception: $exception' : '.'}');
    }
  }

  // If we do not have access to DTD or if we failed to detect the package root
  // by walking the directory structure, default to using a regexp heuristic.
  final directoryRegExp =
      RegExp(r'\/(lib|bin|integration_test|test|benchmark|example)\/.+\.dart');
  final directoryIndex = fileUriString.indexOf(directoryRegExp);
  if (directoryIndex != -1) {
    fileUriString = fileUriString.substring(0, directoryIndex);
  }
  return _assertUriFormatAndReturn(fileUriString);
}