sdk/tests/lib/async/catch_errors.dart

// Copyright (c) 2013, 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.

library catch_errors;

import 'dart:async';

Stream catchErrors(dynamic body()) {
  late StreamController controller;

  bool onError(e, st) {
    controller.add(e);
    return true;
  }

  void onListen() {
    runZonedGuarded(body, onError);
  }

  controller = new StreamController(onListen: onListen);
  return controller.stream;
}

runZonedScheduleMicrotask(
  body(), {
  void onScheduleMicrotask(void callback())?,
  Function? onError,
}) {
  if (onScheduleMicrotask == null) {
    return runZonedGuarded(body, onError as void Function(Object, StackTrace));
  }
  HandleUncaughtErrorHandler? errorHandler;
  if (onError != null) {
    errorHandler =
        (
          Zone self,
          ZoneDelegate parent,
          Zone zone,
          error,
          StackTrace stackTrace,
        ) {
          try {
            return self.parent!.runUnary(
              onError as void Function(Object),
              error,
            );
          } catch (e, s) {
            if (identical(e, error)) {
              return parent.handleUncaughtError(zone, error, stackTrace);
            } else {
              return parent.handleUncaughtError(zone, e, s);
            }
          }
        };
  }
  ScheduleMicrotaskHandler? asyncHandler;
  if (onScheduleMicrotask != null) {
    asyncHandler = (Zone self, ZoneDelegate parent, Zone zone, f()) {
      self.parent!.runUnary(onScheduleMicrotask, () => zone.runGuarded(f));
    };
  }
  ZoneSpecification specification = new ZoneSpecification(
    handleUncaughtError: errorHandler,
    scheduleMicrotask: asyncHandler,
  );
  Zone zone = Zone.current.fork(specification: specification);
  if (onError != null) {
    return zone.runGuarded(body);
  } else {
    return zone.run(body);
  }
}