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// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:async';
import 'package:analysis_server/lsp_protocol/protocol_generated.dart';
import 'package:analysis_server/lsp_protocol/protocol_special.dart';
import 'package:analysis_server/src/analysis_server_abstract.dart';
import 'package:analysis_server/src/domain_abstract.dart';
import 'package:analysis_server/src/lsp/constants.dart';
import 'package:analysis_server/src/lsp/handlers/handler_cancel_request.dart';
import 'package:analysis_server/src/lsp/handlers/handler_reject.dart';
import 'package:analysis_server/src/lsp/json_parsing.dart';
import 'package:analysis_server/src/lsp/lsp_analysis_server.dart';
import 'package:analysis_server/src/lsp/progress.dart';
import 'package:analyzer/dart/analysis/results.dart';
import 'package:analyzer/source/line_info.dart';
import 'package:analyzer_plugin/protocol/protocol.dart';
import 'package:analyzer_plugin/src/protocol/protocol_internal.dart';
/// Converts an iterable using the provided function and skipping over any
/// null values.
Iterable<T> convert<T, E>(Iterable<E> items, T Function(E) converter) {
// TODO(dantup): Now this is used outside of handlers, is there somewhere
// better to put it, and/or a better name for it?
return => item != null);
class CancelableToken extends CancellationToken {
bool _isCancelled = false;
bool get isCancellationRequested => _isCancelled;
void cancel() => _isCancelled = true;
/// A token used to signal cancellation of an operation. This allows computation
/// to be skipped when a caller is no longer interested in the result, for example
/// when a $/cancel request is recieved for an in-progress request.
abstract class CancellationToken {
bool get isCancellationRequested;
abstract class CommandHandler<P, R> with Handler<P, R> {
final LspAnalysisServer server;
Future<ErrorOr<Object?>> handle(List<Object?>? arguments,
ProgressReporter progress, CancellationToken cancellationToken);
mixin Handler<P, R> {
final fileModifiedError = error<R>(ErrorCodes.ContentModified,
'Document was modified before operation completed', null);
LspAnalysisServer get server;
bool fileHasBeenModified(String path, num? clientVersion) {
final serverDocIdentifier = server.getVersionedDocumentIdentifier(path);
return clientVersion != null &&
clientVersion != serverDocIdentifier.version;
ErrorOr<LineInfo> getLineInfo(String path) {
final lineInfo = server.getLineInfo(path);
if (lineInfo == null) {
return error(ServerErrorCodes.InvalidFilePath, 'Invalid file path', path);
} else {
return success(lineInfo);
Future<ErrorOr<ResolvedUnitResult>> requireResolvedUnit(String path) async {
final result = await server.getResolvedUnit(path);
if (result == null) {
return error(ServerErrorCodes.InvalidFilePath, 'Invalid file path', path);
return success(result);
ErrorOr<ParsedUnitResult> requireUnresolvedUnit(String path) {
final result = server.getParsedUnit(path);
if (result == null) {
return error(ServerErrorCodes.InvalidFilePath, 'Invalid file path', path);
return success(result);
mixin LspPluginRequestHandlerMixin<T extends AbstractAnalysisServer>
on RequestHandlerMixin<T> {
Future<List<Response>> requestFromPlugins(
String path,
RequestParams params, {
Duration timeout = const Duration(milliseconds: 500),
}) {
final driver = server.getAnalysisDriver(path);
final pluginFutures = server.pluginManager.broadcastRequest(
contextRoot: driver?.analysisContext?.contextRoot,
return waitForResponses(pluginFutures,
requestParameters: params, timeout: timeout);
/// An object that can handle messages and produce responses for requests.
/// Clients may not extend, implement or mix-in this class.
abstract class MessageHandler<P, R>
with Handler<P, R>, RequestHandlerMixin<LspAnalysisServer> {
final LspAnalysisServer server;
/// The method that this handler can handle.
Method get handlesMessage;
/// A handler that can parse and validate JSON params.
LspJsonHandler<P> get jsonHandler;
FutureOr<ErrorOr<R>> handle(P params, CancellationToken token);
/// Handle the given [message]. If the [message] is a [RequestMessage], then the
/// return value will be sent back in a [ResponseMessage].
/// [NotificationMessage]s are not expected to return results.
FutureOr<ErrorOr<R>> handleMessage(
IncomingMessage message, CancellationToken token) {
final reporter = LspJsonReporter('params');
if (!jsonHandler.validateParams(message.params, reporter)) {
return error(
'Invalid params for ${message.method}:\n'
'${reporter.errors.isNotEmpty ? reporter.errors.first : ''}'
final params = message.params != null
? jsonHandler.convertParams(message.params)
: null as P;
return handle(params, token);
class NotCancelableToken extends CancellationToken {
bool get isCancellationRequested => false;
/// A message handler that handles all messages for a given server state.
abstract class ServerStateMessageHandler {
final LspAnalysisServer server;
final Map<Method, MessageHandler> _messageHandlers = {};
final CancelRequestHandler _cancelHandler;
final NotCancelableToken _notCancelableToken = NotCancelableToken();
: _cancelHandler = CancelRequestHandler(server) {
/// Handle the given [message]. If the [message] is a [RequestMessage], then the
/// return value will be sent back in a [ResponseMessage].
/// [NotificationMessage]s are not expected to return results.
FutureOr<ErrorOr<Object?>> handleMessage(IncomingMessage message) async {
final handler = _messageHandlers[message.method];
if (handler == null) {
return handleUnknownMessage(message);
if (message is! RequestMessage) {
return handler.handleMessage(message, _notCancelableToken);
// Create a cancellation token that will allow us to cancel this request if
// requested to save processing (the handler will need to specifically
// check the token after `await` points).
final token = _cancelHandler.createToken(message);
try {
final result = await handler.handleMessage(message, token);
// Do a final check before returning the result, because if the request was
// cancelled we can save the overhead of serialising everything to JSON
// and the client to deserialising the same in order to read the ID to see
// that it was a request it didn't need (in the case of completions this
// can be quite large).
await Future.delayed(;
return token.isCancellationRequested ? cancelled() : result;
} finally {
FutureOr<ErrorOr<Object?>> handleUnknownMessage(IncomingMessage message) {
// If it's an optional *Notification* we can ignore it (return success).
// Otherwise respond with failure. Optional Requests must still be responded
// to so they don't leave open requests on the client.
return _isOptionalNotification(message)
? success(null)
: error(ErrorCodes.MethodNotFound, 'Unknown method ${message.method}');
void registerHandler(MessageHandler handler) {
_messageHandlers[handler.handlesMessage] = handler;
void reject(Method method, ErrorCodes code, String message) {
registerHandler(RejectMessageHandler(server, method, code, message));
bool _isOptionalNotification(IncomingMessage message) {
// Not a notification.
if (message is! NotificationMessage) {
return false;
// Messages that start with $/ are optional.
final stringValue = message.method.toJson();
return stringValue is String && stringValue.startsWith(r'$/');