completion method
Completion proposals at line:character.
Implementation
Future<Map<String, Object?>> completion(
String language,
String source,
int line,
int character, {
String? uri,
}) => _withDoc(language, source, uri: uri, (lsp, docUri) async {
final list = await lsp.completion(docUri, Position(line, character));
return <String, Object?>{'completion': list.toJson(), 'isError': false};
});