Generate all runtime files from dart.

lib/runtime/dart/_generators.js

-// Copyright (c) 2015, 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.
-
-/**
- * This library adapts ES6 generators to implement Dart's async/await.
- *
- * It's designed to interact with Dart's Future/Stream and follow Dart
- * async/await semantics.
- *
- * See https://github.com/dart-lang/dev_compiler/issues/245 for ideas on
- * reconciling Dart's Future and ES6 Promise.
- *
- * Inspired by `co`: https://github.com/tj/co/blob/master/index.js, which is a
- * stepping stone for proposed ES7 async/await, and uses ES6 Promises.
- */
-dart_library.library('dart/_generators', null, /* Imports */[
-], /* Lazy Imports */[
-  'dart/_operations',
-  'dart/_js_helper',
-  'dart/core',
-  'dart/collection',
-  'dart/async'
-], function(exports, _operations, _js_helper, core, collection, async) {
-  'use strict';
-
-  const _jsIterator = Symbol('_jsIterator');
-  const _current = Symbol('_current');
-
-  function syncStar(gen, E, ...args) {
-    const SyncIterable_E = _js_helper.SyncIterable$(E);
-    return new SyncIterable_E(gen, args);
-  }
-  exports.syncStar = syncStar;
-
-  function async_(gen, T, ...args) {
-    let iter;
-    function onValue(res) {
-      if (res === void 0) res = null;
-      return next(iter.next(res));
-    }
-    function onError(err) {
-      // If the awaited Future throws, we want to convert this to an exception
-      // thrown from the `yield` point, as if it was thrown there.
-      //
-      // If the exception is not caught inside `gen`, it will emerge here, which
-      // will send it to anyone listening on this async function's Future<T>.
-      //
-      // In essence, we are giving the code inside the generator a chance to
-      // use try-catch-finally.
-      return next(iter.throw(err));
-    }
-    function next(ret) {
-      if (ret.done) return ret.value;
-      // Checks if the awaited value is a Future.
-      let future = ret.value;
-      if (!_operations.instanceOf(future, async.Future$)) {
-        future = async.Future.value(future);
-      }
-      // Chain the Future so `await` receives the Future's value.
-      return future.then(onValue, {onError: onError});
-    }
-    return async.Future$(T).new(function() {
-      iter = gen(...args)[Symbol.iterator]();
-      return onValue();
-    });
-  }
-  exports.async = async_;
-
-  // Implementation inspired by _AsyncStarStreamController in
-  // dart-lang/sdk's runtime/lib/core_patch.dart
-  //
-  // Given input like:
-  //
-  //     foo() async* {
-  //       yield 1;
-  //       yield* bar();
-  //       print(await baz());
-  //     }
-  //
-  // This generates as:
-  //
-  //    function foo() {
-  //      return dart.asyncStar(function*(stream) {
-  //        if (stream.add(1)) return;
-  //        yield;
-  //        if (stream.addStream(bar()) return;
-  //        yield;
-  //        print(yield baz());
-  //      });
-  //    }
-  class _AsyncStarStreamController {
-    constructor(generator, T, args) {
-      this.isAdding = false;
-      this.isWaiting = false;
-      this.isScheduled = false;
-      this.isSuspendedAtYield = false;
-      this.canceler = null;
-      this.iterator = generator(this, ...args)[Symbol.iterator]();
-      this.controller = async.StreamController$(T).new({
-        onListen: () => this.scheduleGenerator(),
-        onResume: () => this.onResume(),
-        onCancel: () => this.onCancel()
-      });
-    }
-
-    onResume() {
-      if (this.isSuspendedAtYield) {
-        this.scheduleGenerator();
-      }
-    }
-
-    onCancel() {
-      if (this.controller.isClosed) {
-        return null;
-      }
-      if (this.canceler == null) {
-        this.canceler = async.Completer.new();
-        this.scheduleGenerator();
-      }
-      return this.canceler.future;
-    }
-
-    close() {
-      if (this.canceler != null && !this.canceler.isCompleted) {
-        // If the stream has been cancelled, complete the cancellation future
-        // with the error.
-        this.canceler.complete();
-      }
-      this.controller.close();
-    }
-
-    scheduleGenerator() {
-      // TODO(jmesserly): is this paused check in the right place? Assuming the
-      // async* Stream yields, then is paused (by other code), the body will
-      // already be scheduled. This will cause at least one more iteration to
-      // run (adding another data item to the Stream) before actually pausing.
-      // It could be fixed by moving the `isPaused` check inside `runBody`.
-      if (this.isScheduled || this.controller.isPaused ||
-          this.isAdding || this.isWaiting) {
-        return;
-      }
-      this.isScheduled = true;
-      async.scheduleMicrotask(() => this.runBody());
-    }
-
-    runBody(opt_awaitValue) {
-      this.isScheduled = false;
-      this.isSuspendedAtYield = false;
-      this.isWaiting = false;
-      let iter;
-      try {
-        iter = this.iterator.next(opt_awaitValue);
-      } catch (e) {
-        this.addError(e, _operations.stackTrace(e));
-        this.close();
-        return;
-      }
-      if (iter.done) {
-        this.close();
-        return;
-      }
-
-      // If we're suspended at a yield/yield*, we're done for now.
-      if (this.isSuspendedAtYield || this.isAdding) return;
-
-      // Handle `await`: if we get a value passed to `yield` it means we are
-      // waiting on this Future. Make sure to prevent scheduling, and pass the
-      // value back as the result of the `yield`.
-      //
-      // TODO(jmesserly): is the timing here correct? The assumption here is
-      // that we should schedule `await` in `async*` the same as in `async`.
-      this.isWaiting = true;
-      let future = iter.value;
-      if (!_operations.instanceOf(future, async.Future$)) {
-        future = async.Future.value(future);
-      }
-      return future.then((x) => this.runBody(x),
-          { onError: (e, s) => this.throwError(e, s) });
-    }
-
-    // Adds element to stream, returns true if the caller should terminate
-    // execution of the generator.
-    add(event) {
-      // If stream is cancelled, tell caller to exit the async generator.
-      if (!this.controller.hasListener) return true;
-      this.controller.add(event);
-      this.scheduleGenerator();
-      this.isSuspendedAtYield = true;
-      return false;
-    }
-
-    // Adds the elements of stream into this controller's stream.
-    // The generator will be scheduled again when all of the
-    // elements of the added stream have been consumed.
-    // Returns true if the caller should terminate
-    // execution of the generator.
-    addStream(stream) {
-      // If stream is cancelled, tell caller to exit the async generator.
-      if (!this.controller.hasListener) return true;
-
-      this.isAdding = true;
-      this.controller.addStream(stream, {cancelOnError: false}).then(() => {
-        this.isAdding = false;
-        this.scheduleGenerator();
-      }, { onError: (e, s) => this.throwError(e, s) });
-    }
-
-    throwError(error, stackTrace) {
-      try {
-        this.iterator.throw(error);
-      } catch (e) {
-        this.addError(e, stackTrace);
-      }
-    }
-
-    addError(error, stackTrace) {
-      if ((this.canceler != null) && !this.canceler.isCompleted) {
-        // If the stream has been cancelled, complete the cancellation future
-        // with the error.
-        this.canceler.completeError(error, stackTrace);
-        return;
-      }
-      if (!this.controller.hasListener) return;
-      this.controller.addError(error, stackTrace);
-    }
-  }
-
-  /** Returns a Stream of T implemented by an async* function. */
-  function asyncStar(gen, T, ...args) {
-    return new _AsyncStarStreamController(gen, T, args).controller.stream;
-  }
-  exports.asyncStar = asyncStar;
-});