updateRoots method

@mustCallSuper Future<void> updateRoots()

Updates the list of roots by calling listRoots.

Normalizes file paths to file: URIs to handle clients which do not follow the spec exactly.

If the current _rootsCompleter was not yet completed, then we wait to complete it until we get an updated list of roots, so that we don't get stale results from listRoots requests that are still in flight during a change notification.

Implementation

@mustCallSuper
Future<void> updateRoots() async {
  _rootsState = _RootsState.pending;
  final previousCompleter = _rootsCompleter;

  // Always create a new completer so we can handle race conditions by
  // checking completer identity.
  final newCompleter = _rootsCompleter = Completer();
  _roots = null;

  if (previousCompleter != null) {
    // Complete previously scheduled completers with our completers value.
    previousCompleter.complete(newCompleter.future);
  }

  ListRootsResult? result;
  try {
    result = await listRoots(ListRootsRequest());
  } on RpcException catch (e) {
    log(LoggingLevel.error, 'Error calling listRoots: $e');
  } finally {
    // Only complete the completer if it's still the one we created. Otherwise
    // we wait for the next result to come back and throw away this result.
    if (_rootsCompleter == newCompleter) {
      final roots =
          (result == null ? <Root>[] : result.roots)
              .map<Root?>((root) {
                // Some clients just give file paths, but the spec states they
                // should be file: URIs. This converts paths to file: URIs to
                // paper over that issue.
                final parsedUri = Uri.tryParse(root.uri);
                if (parsedUri == null) {
                  log(
                    LoggingLevel.warning,
                    'Invalid root given from client ${root.uri}',
                  );
                  return null;
                }
                // No scheme or the scheme actually looks like a windows drive
                // letter, convert it to a file: URI.
                if (!parsedUri.hasScheme || parsedUri.scheme.length == 1) {
                  return Root(
                    uri: Uri.file(root.uri).toString(),
                    name: root.name,
                  );
                }
                return root;
              })
              // `.nonNulls` gives us a type of Object here due to the
              // extension types, so we use `whereType` instead
              .whereType<Root>()
              .toList();
      newCompleter.complete(roots);
      _roots = roots;
      _rootsCompleter = null;
      _rootsState = _RootsState.upToDate;
    }
  }
}