dart-sass/test/node_api/intercept_stdout.dart

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// Copyright 2018 Google Inc. Use of this source code is governed by an
// MIT-style license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT.
import 'dart:async';
import 'package:js/js.dart';
typedef _InterceptStdout = void Function() Function(
String Function(String), String Function(String));
@JS('require')
external _InterceptStdout _require(String name);
final _interceptStdout = _require("intercept-stdout");
/// All output that would be printed to stderr is instead piped through that
/// stream as long as it has a listener.
///
/// Note that the piped text is not necessarily separated by lines.
Stream<String> interceptStderr() {
void Function() unhook;
StreamController<String> controller;
controller = new StreamController(onListen: () {
unhook = _interceptStdout(null, allowInterop((text) {
controller.add(text);
return "";
}));
}, onCancel: () {
unhook();
});
return controller.stream;
}