blob: f1989a7986bf9373a2ee52d4dd646ec30f7f3efa [file] [log] [blame]
// Copyright (c) 2014, 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:stream_channel/stream_channel.dart';
import '../error_code.dart' as error_code;
import 'exception.dart';
typedef ZeroArgumentFunction = Function();
/// Returns a sentence fragment listing the elements of [iter].
/// This converts each element of [iter] to a string and separates them with
/// commas and/or "and" where appropriate.
String toSentence(Iterable iter) {
if (iter.length == 1) return iter.first.toString();
return iter.take(iter.length - 1).join(', ') + ' and ${iter.last}';
/// Returns [name] if [number] is 1, or the plural of [name] otherwise.
/// By default, this just adds "s" to the end of [name] to get the plural. If
/// [plural] is passed, that's used instead.
String pluralize(String name, int number, {String plural}) {
if (number == 1) return name;
if (plural != null) return plural;
return '${name}s';
/// A regular expression to match the exception prefix that some exceptions'
/// [Object.toString] values contain.
final _exceptionPrefix = RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');
/// Get a string description of an exception.
/// Many exceptions include the exception class name at the beginning of their
/// [toString], so we remove that if it exists.
String getErrorMessage(error) =>
error.toString().replaceFirst(_exceptionPrefix, '');
/// Like `try`/`finally`, run [body] and ensure that [whenComplete] runs
/// afterwards, regardless of whether [body] succeeded.
/// This is synchronicity-agnostic relative to [body]. If [body] returns a
/// [Future], this wil run asynchronously; otherwise it will run synchronously.
void tryFinally(Function() body, Function() whenComplete) {
var result;
try {
result = body();
} catch (_) {
if (result is! Future) {
return result;
} else {
return result.whenComplete(whenComplete);
/// A transformer that silently drops [FormatException]s.
final ignoreFormatExceptions = StreamTransformer<Object, Object>.fromHandlers(
handleError: (error, stackTrace, sink) {
if (error is FormatException) return;
sink.addError(error, stackTrace);
/// A transformer that sends error responses on [FormatException]s.
final StreamChannelTransformer respondToFormatExceptions =
/// The implementation of [respondToFormatExceptions].
class _RespondToFormatExceptionsTransformer
implements StreamChannelTransformer {
StreamChannel bind(StreamChannel channel) {
var transformed;
transformed = channel.changeStream((stream) {
return stream.handleError((error) {
if (error is! FormatException) throw error;
var exception = RpcException(
error_code.PARSE_ERROR, 'Invalid JSON: ${error.message}');
return transformed;
/// Returns a [StreamSink] that wraps [sink] and maps each event added using
/// [callback].
StreamSink mapStreamSink(StreamSink sink, Function(dynamic) callback) =>
_MappedStreamSink(sink, callback);
/// A [StreamSink] wrapper that maps each event added to the sink.
class _MappedStreamSink implements StreamSink {
final StreamSink _inner;
final Function _callback;
Future get done => _inner.done;
_MappedStreamSink(this._inner, this._callback);
void add(event) => _inner.add(_callback(event));
void addError(error, [StackTrace stackTrace]) =>
_inner.addError(error, stackTrace);
Future addStream(Stream stream) => _inner.addStream(;
Future close() => _inner.close();