dart2js: Don't zone-register callbacks in async functions for every await.

sdk/lib/_internal/js_runtime/lib/js_helper.dart

Index: sdk/lib/_internal/js_runtime/lib/js_helper.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_helper.dart b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
index eb2cd55caf428d8bc5cbcbc1e66f6df5c351a0d5..65759fd1d24c4721e91b3b1826ae149126286e21 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_helper.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
@@ -4,8 +4,6 @@
 
 library _js_helper;
 
-import 'dart:_async_await_error_codes' as async_error_codes;
-
 import 'dart:_js_embedded_names' show
     DEFERRED_LIBRARY_URIS,
     DEFERRED_LIBRARY_HASHES,
@@ -2047,6 +2045,15 @@ class UnknownJsTypeError extends Error {
   String toString() => _message.isEmpty ? 'Error' : 'Error: $_message';
 }
 
+/// A wrapper around an exception, much like the one created by [wrapException]
+/// but with a pre-given stack-trace.
+class ExceptionAndStackTrace {

[Lasse Reichstein Nielsen, 2015/08/12 09:46:55]

See dart:async's AsyncError. It has final members and a toString, but otherwise
it's the same.

[floitsch, 2015/08/12 14:53:44]

But it's publicly visible...

+  dynamic dartException;
+  StackTrace stackTrace;
+
+  ExceptionAndStackTrace(this.dartException, this.stackTrace);
+}
+
 /**
  * Called from catch blocks in generated code to extract the Dart
  * exception from the thrown value. The thrown value may have been
@@ -3886,373 +3893,3 @@ void badMain() {
 void mainHasTooManyParameters() {
   throw new MainError("'main' expects too many parameters.");
 }
-
-/// A wrapper around an exception, much like the one created by [wrapException]
-/// but with a pre-given stack-trace.
-class ExceptionAndStackTrace {
-  dynamic dartException;
-  StackTrace stackTrace;
-
-  ExceptionAndStackTrace(this.dartException, this.stackTrace);
-}
-
-/// Runtime support for async-await transformation.
-///
-/// This function is called by a transformed function on each await and return
-/// in the untransformed function, and before starting.
-///
-/// If [object] is not a future it will be wrapped in a `new Future.value`.
-///
-/// If [asyncBody] is [async_error_codes.SUCCESS]/[async_error_codes.ERROR] it
-/// indicates a return or throw from the async function, and
-/// complete/completeError is called on [completer] with [object].
-///
-/// Otherwise [asyncBody] is set up to be called when the future is completed
-/// with a code [async_error_codes.SUCCESS]/[async_error_codes.ERROR] depending
-/// on the success of the future.
-///
-/// Returns the future of the completer for convenience of the first call.
-dynamic asyncHelper(dynamic object,
-    dynamic /* int | WrappedAsyncBody */ bodyFunctionOrErrorCode,
-    Completer completer) {
-  if (identical(bodyFunctionOrErrorCode, async_error_codes.SUCCESS)) {
-    completer.complete(object);
-    return;
-  } else if (identical(bodyFunctionOrErrorCode, async_error_codes.ERROR)) {
-    // The error is a js-error.
-    completer.completeError(unwrapException(object),
-                            getTraceFromException(object));
-    return;
-  }
-  Future future = object is Future ? object : new Future.value(object);
-  future.then(
-      (result) => bodyFunctionOrErrorCode(async_error_codes.SUCCESS, result),
-      onError: (dynamic error, StackTrace stackTrace) {
-        ExceptionAndStackTrace wrappedException =
-            new ExceptionAndStackTrace(error, stackTrace);
-        bodyFunctionOrErrorCode(async_error_codes.ERROR, wrappedException);
-      });
-  return completer.future;
-}
-
-typedef void WrappedAsyncBody(int errorCode, dynamic result);
-
-WrappedAsyncBody _wrapJsFunctionForAsync(dynamic /* js function */ function) {
-  var protected = JS('', """
-    // Invokes [function] with [errorCode] and [result].
-    //
-    // If (and as long as) the invocation throws, calls [function] again,
-    // with an error-code.
-    function(errorCode, result) {
-      while (true) {
-        try {
-          #(errorCode, result);
-          break;
-        } catch (error) {
-          result = error;
-          errorCode = #;
-        }
-      }
-    }""", function, async_error_codes.ERROR);
-  return Zone.current.bindBinaryCallback((int errorCode, dynamic result) {
-    JS('', '#(#, #)', protected, errorCode, result);
-  });
-}
-
-/// Implements the runtime support for async* functions.
-///
-/// Called by the transformed function for each original return, await, yield,
-/// yield* and before starting the function.
-///
-/// When the async* function wants to return it calls this function with
-/// [asyncBody] == [async_error_codes.SUCCESS], the asyncStarHelper takes this
-/// as signal to close the stream.
-///
-/// When the async* function wants to signal that an uncaught error was thrown,
-/// it calls this function with [asyncBody] == [async_error_codes.ERROR],
-/// the streamHelper takes this as signal to addError [object] to the
-/// [controller] and close it.
-///
-/// If the async* function wants to do a yield or yield*, it calls this function
-/// with [object] being an [IterationMarker].
-///
-/// In the case of a yield or yield*, if the stream subscription has been
-/// canceled, schedules [asyncBody] to be called with
-/// [async_error_codes.STREAM_WAS_CANCELED].
-///
-/// If [object] is a single-yield [IterationMarker], adds the value of the
-/// [IterationMarker] to the stream. If the stream subscription has been
-/// paused, return early. Otherwise schedule the helper function to be
-/// executed again.
-///
-/// If [object] is a yield-star [IterationMarker], starts listening to the
-/// yielded stream, and adds all events and errors to our own controller (taking
-/// care if the subscription has been paused or canceled) - when the sub-stream
-/// is done, schedules [asyncBody] again.
-///
-/// If the async* function wants to do an await it calls this function with
-/// [object] not and [IterationMarker].
-///
-/// If [object] is not a [Future], it is wrapped in a `Future.value`.
-/// The [asyncBody] is called on completion of the future (see [asyncHelper].
-void asyncStarHelper(dynamic object,
-    dynamic /* int | WrappedAsyncBody */ bodyFunctionOrErrorCode,
-    AsyncStarStreamController controller) {
-  if (identical(bodyFunctionOrErrorCode, async_error_codes.SUCCESS)) {
-    // This happens on return from the async* function.
-    if (controller.isCanceled) {
-      controller.cancelationCompleter.complete();
-    } else {
-      controller.close();
-    }
-    return;
-  } else if (identical(bodyFunctionOrErrorCode, async_error_codes.ERROR)) {
-    // The error is a js-error.
-    if (controller.isCanceled) {
-      controller.cancelationCompleter.completeError(
-          unwrapException(object),
-          getTraceFromException(object));
-    } else {
-      controller.addError(unwrapException(object),
-                          getTraceFromException(object));
-      controller.close();
-    }
-    return;
-  }
-
-  if (object is IterationMarker) {
-    if (controller.isCanceled) {
-      bodyFunctionOrErrorCode(async_error_codes.STREAM_WAS_CANCELED, null);
-      return;
-    }
-    if (object.state == IterationMarker.YIELD_SINGLE) {
-      controller.add(object.value);
-
-      scheduleMicrotask(() {
-        if (controller.isPaused) {
-          // We only suspend the thread inside the microtask in order to allow
-          // listeners on the output stream to pause in response to the just
-          // output value, and have the stream immediately stop producing.
-          controller.isSuspended = true;
-          return;
-        }
-        bodyFunctionOrErrorCode(null, async_error_codes.SUCCESS);
-      });
-      return;
-    } else if (object.state == IterationMarker.YIELD_STAR) {
-      Stream stream = object.value;
-      // Errors of [stream] are passed though to the main stream. (see
-      // [AsyncStreamController.addStream]).
-      // TODO(sigurdm): The spec is not very clear here. Clarify with Gilad.
-      controller.addStream(stream).then((_) {
-        // No check for isPaused here because the spec 17.16.2 only
-        // demands checks *before* each element in [stream] not after the last
-        // one. On the other hand we check for isCanceled, as that check happens
-        // after insertion of each element.
-        int errorCode = controller.isCanceled
-            ? async_error_codes.STREAM_WAS_CANCELED
-            : async_error_codes.SUCCESS;
-        bodyFunctionOrErrorCode(errorCode, null);
-      });
-      return;
-    }
-  }
-
-  Future future = object is Future ? object : new Future.value(object);
-  future.then(
-      (result) => bodyFunctionOrErrorCode(async_error_codes.SUCCESS, result),
-      onError: (error, StackTrace stackTrace) {
-        ExceptionAndStackTrace wrappedException =
-            new ExceptionAndStackTrace(error, stackTrace);
-        bodyFunctionOrErrorCode(async_error_codes.ERROR, wrappedException);
-      });
-}
-
-Stream streamOfController(AsyncStarStreamController controller) {
-  return controller.stream;
-}
-
-/// A wrapper around a [StreamController] that keeps track of the state of
-/// the execution of an async* function.
-/// It can be in 1 of 3 states:
-///
-/// - running/scheduled
-/// - suspended
-/// - canceled
-///
-/// If yielding while the subscription is paused it will become suspended. And
-/// only resume after the subscription is resumed or canceled.
-class AsyncStarStreamController {
-  StreamController controller;
-  Stream get stream => controller.stream;
-
-  /// True when the async* function has yielded while being paused.
-  /// When true execution will only resume after a `onResume` or `onCancel`
-  /// event.
-  bool isSuspended = false;
-
-  bool get isPaused => controller.isPaused;
-
-  Completer cancelationCompleter = null;
-
-  /// True after the StreamSubscription has been cancelled.
-  /// When this is true, errors thrown from the async* body should go to the
-  /// [cancelationCompleter] instead of adding them to [controller], and
-  /// returning from the async function should complete [cancelationCompleter].
-  bool get isCanceled => cancelationCompleter != null;
-
-  add(event) => controller.add(event);
-
-  addStream(Stream stream) {
-    return controller.addStream(stream, cancelOnError: false);
-  }
-
-  addError(error, stackTrace) => controller.addError(error, stackTrace);
-
-  close() => controller.close();
-
-  AsyncStarStreamController(WrappedAsyncBody body) {
-
-    _resumeBody() {
-      scheduleMicrotask(() {
-        body(async_error_codes.SUCCESS, null);
-      });
-    }
-
-    controller = new StreamController(
-      onListen: () {
-        _resumeBody();
-      }, onResume: () {
-        // Only schedule again if the async* function actually is suspended.
-        // Resume directly instead of scheduling, so that the sequence
-        // `pause-resume-pause` will result in one extra event produced.
-        if (isSuspended) {
-          isSuspended = false;
-          _resumeBody();
-        }
-      }, onCancel: () {
-        // If the async* is finished we ignore cancel events.
-        if (!controller.isClosed) {
-          cancelationCompleter = new Completer();
-          if (isSuspended) {
-            // Resume the suspended async* function to run finalizers.
-            isSuspended = false;
-            scheduleMicrotask(() {
-              body(async_error_codes.STREAM_WAS_CANCELED, null);
-            });
-          }
-          return cancelationCompleter.future;
-        }
-      });
-  }
-}
-
-makeAsyncStarController(body) {
-  return new AsyncStarStreamController(body);
-}
-
-class IterationMarker {
-  static const YIELD_SINGLE = 0;
-  static const YIELD_STAR = 1;
-  static const ITERATION_ENDED = 2;
-  static const UNCAUGHT_ERROR = 3;
-
-  final value;
-  final int state;
-
-  IterationMarker._(this.state, this.value);
-
-  static yieldStar(dynamic /* Iterable or Stream */ values) {
-    return new IterationMarker._(YIELD_STAR, values);
-  }
-
-  static endOfIteration() {
-    return new IterationMarker._(ITERATION_ENDED, null);
-  }
-
-  static yieldSingle(dynamic value) {
-    return new IterationMarker._(YIELD_SINGLE, value);
-  }
-
-  static uncaughtError(dynamic error) {
-    return new IterationMarker._(UNCAUGHT_ERROR, error);
-  }
-
-  toString() => "IterationMarker($state, $value)";
-}
-
-class SyncStarIterator implements Iterator {
-  final dynamic _body;
-
-  // If [runningNested] this is the nested iterator, otherwise it is the
-  // current value.
-  dynamic _current = null;
-  bool _runningNested = false;
-
-  get current => _runningNested ? _current.current : _current;
-
-  SyncStarIterator(this._body);
-
-  _runBody() {
-    return JS('', '''
-      // Invokes [body] with [errorCode] and [result].
-      //
-      // If (and as long as) the invocation throws, calls [function] again,
-      // with an error-code.
-      (function(body) {
-        var errorValue, errorCode = #;
-        while (true) {
-          try {
-            return body(errorCode, errorValue);
-          } catch (error) {
-            errorValue = error;
-            errorCode = #
-          }
-        }
-      })(#)''', async_error_codes.SUCCESS, async_error_codes.ERROR, _body);
-  }
-
-
-  bool moveNext() {
-    if (_runningNested) {
-      if (_current.moveNext()) {
-        return true;
-      } else {
-        _runningNested = false;
-      }
-    }
-    _current = _runBody();
-    if (_current is IterationMarker) {
-      if (_current.state == IterationMarker.ITERATION_ENDED) {
-        _current = null;
-        // Rely on [_body] to repeatedly return `ITERATION_ENDED`.
-        return false;
-      } else if (_current.state == IterationMarker.UNCAUGHT_ERROR) {
-        // Rely on [_body] to repeatedly return `UNCAUGHT_ERROR`.
-        // This is a wrapped exception, so we use JavaScript throw to throw it.
-        JS('', 'throw #', _current.value);
-      } else {
-        assert(_current.state == IterationMarker.YIELD_STAR);
-        _current = _current.value.iterator;
-        _runningNested = true;
-        return moveNext();
-      }
-    }
-    return true;
-  }
-}
-
-/// An Iterable corresponding to a sync* method.
-///
-/// Each invocation of a sync* method will return a new instance of this class.
-class SyncStarIterable extends IterableBase {
-  // This is a function that will return a helper function that does the
-  // iteration of the sync*.
-  //
-  // Each invocation should give a body with fresh state.
-  final dynamic /* js function */ _outerHelper;
-
-  SyncStarIterable(this._outerHelper);
-
-  Iterator get iterator => new SyncStarIterator(JS('', '#()', _outerHelper));
-}