Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/barback/lib/src/asset/asset_node.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 barback.asset.asset_node;
+
+import 'dart:async';
+
+import '../errors.dart';
+import '../graph/transform_node.dart';
+import '../utils.dart';
+import 'asset.dart';
+import 'asset_id.dart';
+
+/// Describes the current state of an asset as part of a transformation graph.
+///
+/// An asset node can be in one of three states (see [AssetState]). It provides
+/// an [onStateChange] stream that emits an event whenever it changes state.
+///
+/// Asset nodes are controlled using [AssetNodeController]s.
+class AssetNode {
+  /// The id of the asset that this node represents.
+  final AssetId id;
+
+  /// The [AssetNode] from which [this] is forwarded.
+  ///
+  /// For nodes that aren't forwarded, this will return [this]. Otherwise, it
+  /// will return the first node in the forwarding chain.
+  ///
+  /// This is used to determine whether two nodes are forwarded from the same
+  /// source.
+  AssetNode get origin => _origin == null ? this : _origin;
+  AssetNode _origin;
+
+  /// The transform that created this asset node.
+  ///
+  /// This is `null` for source assets. It can change if the upstream transform
+  /// that created this asset changes; this change will *not* cause an
+  /// [onStateChange] event.
+  TransformNode get transform => _transform;
+  TransformNode _transform;
+
+  /// The current state of the asset node.
+  AssetState get state => _state;
+  AssetState _state;
+
+  /// The concrete asset that this node represents.
+  ///
+  /// This is null unless [state] is [AssetState.AVAILABLE].
+  Asset get asset => _asset;
+  Asset _asset;
+
+  /// The callback to be called to notify this asset node's creator that the
+  /// concrete asset should be generated.
+  ///
+  /// This is null for non-lazy asset nodes (see [AssetNodeController.lazy]).
+  /// Once this is called, it's set to null and [this] is no longer considered
+  /// lazy.
+  Function _lazyCallback;
+
+  /// Whether this node is lazy, meaning that [force] must be called to
+  /// guarantee that it will eventually become available.
+  bool get isLazy => _lazyCallback != null ||
+      (_origin != null && _origin.isLazy);
+
+  /// A broadcast stream that emits an event whenever the node changes state.
+  ///
+  /// This stream is synchronous to ensure that when a source asset is modified
+  /// or removed, the appropriate portion of the asset graph is dirtied before
+  /// any [Barback.getAssetById] calls emit newly-incorrect values.
+  Stream<AssetState> get onStateChange => _stateChangeController.stream;
+
+  /// This is synchronous so that a source being updated will always be
+  /// propagated through the build graph before anything that depends on it is
+  /// requested.
+  final _stateChangeController =
+      new StreamController<AssetState>.broadcast(sync: true);
+
+  /// Calls [callback] when the node's asset is available.
+  ///
+  /// If the asset is currently available, this calls [callback] synchronously
+  /// to ensure that the asset is still available.
+  ///
+  /// The return value of [callback] is piped to the returned Future. If the
+  /// asset is removed before becoming available, the returned future will throw
+  /// an [AssetNotFoundException].
+  Future whenAvailable(callback(Asset asset)) {
+    return _waitForState((state) => state.isAvailable || state.isRemoved,
+        (state) {
+      if (state.isRemoved) throw new AssetNotFoundException(id);
+      return callback(asset);
+    });
+  }
+
+  /// Calls [callback] when the node's asset is removed.
+  ///
+  /// If the asset is already removed when this is called, it calls [callback]
+  /// synchronously.
+  ///
+  /// The return value of [callback] is piped to the returned Future.
+  Future whenRemoved(callback()) =>
+    _waitForState((state) => state.isRemoved, (_) => callback());
+
+  /// Returns a [Future] that completes when [state] changes from its current
+  /// value to any other value.
+  ///
+  /// The returned [Future] will contain the new state.
+  Future<AssetState> whenStateChanges() {
+    var startState = state;
+    return _waitForState((state) => state != startState, (state) => state);
+  }
+
+  /// Calls [callback] as soon as the node is in a state that matches [test].
+  ///
+  /// [callback] is called synchronously if this is already in such a state.
+  ///
+  /// The return value of [callback] is piped to the returned Future.
+  Future _waitForState(bool test(AssetState state),
+      callback(AssetState state)) {
+    if (test(state)) return syncFuture(() => callback(state));
+    return onStateChange.firstWhere(test).then((_) => callback(state));
+  }
+
+  AssetNode._(this.id, this._transform, this._origin)
+      : _state = AssetState.RUNNING;
+
+  AssetNode._available(Asset asset, this._transform, this._origin)
+      : id = asset.id,
+        _asset = asset,
+        _state = AssetState.AVAILABLE;
+
+  AssetNode._lazy(this.id, this._transform, this._origin, this._lazyCallback)
+      : _state = AssetState.RUNNING;
+
+  /// If [this] is lazy, force it to generate a concrete asset; otherwise, do
+  /// nothing.
+  ///
+  /// See [AssetNodeController.lazy].
+  void force() {
+    if (_origin != null) {
+      _origin.force();
+    } else if (_lazyCallback != null) {
+      _lazyCallback();
+      _lazyCallback = null;
+    }
+  }
+
+  String toString() => "${isLazy ? 'lazy' : state} asset $id";
+}
+
+/// The controller for an [AssetNode].
+///
+/// This controls which state the node is in.
+class AssetNodeController {
+  final AssetNode node;
+
+  /// Creates a controller for a dirty node.
+  AssetNodeController(AssetId id, [TransformNode transform])
+      : node = new AssetNode._(id, transform, null);
+
+  /// Creates a controller for an available node with the given concrete
+  /// [asset].
+  AssetNodeController.available(Asset asset, [TransformNode transform])
+      : node = new AssetNode._available(asset, transform, null);
+
+  /// Creates a controller for a lazy node.
+  ///
+  /// For the most part, this node works like any other dirty node. However, the
+  /// owner of its controller isn't expected to do the work to make it available
+  /// as soon as possible like they would for a non-lazy node. Instead, when its
+  /// value is needed, [callback] will fire to indicate that it should be made
+  /// available as soon as possible.
+  ///
+  /// [callback] is guaranteed to only fire once.
+  AssetNodeController.lazy(AssetId id, void callback(),
+          [TransformNode transform])
+      : node = new AssetNode._lazy(id, transform, null, callback);
+
+  /// Creates a controller for a node whose initial state matches the current
+  /// state of [node].
+  ///
+  /// [AssetNode.origin] of the returned node will automatically be set to
+  /// `node.origin`.
+  ///
+  /// If [node] is lazy, the returned node will also be lazy.
+  AssetNodeController.from(AssetNode node)
+      : node = new AssetNode._(node.id, node.transform, node.origin) {
+    if (node.state.isAvailable) {
+      setAvailable(node.asset);
+    } else if (node.state.isRemoved) {
+      setRemoved();
+    }
+  }
+
+  /// Marks the node as [AssetState.RUNNING].
+  void setDirty() {
+    assert(node._state != AssetState.REMOVED);
+    node._asset = null;
+    node._lazyCallback = null;
+
+    // Don't re-emit a dirty event to avoid cases where we try to dispatch an
+    // event while handling another event (e.g. an output is marked lazy, which
+    // causes it to be forced, which causes it to be marked dirty).
+    if (node._state.isDirty) return;
+    node._state = AssetState.RUNNING;
+    node._stateChangeController.add(AssetState.RUNNING);
+  }
+
+  /// Marks the node as [AssetState.REMOVED].
+  ///
+  /// Once a node is marked as removed, it can't be marked as any other state.
+  /// If a new asset is created with the same id, it will get a new node.
+  void setRemoved() {
+    assert(node._state != AssetState.REMOVED);
+    node._state = AssetState.REMOVED;
+    node._asset = null;
+    node._lazyCallback = null;
+    node._stateChangeController.add(AssetState.REMOVED);
+  }
+
+  /// Marks the node as [AssetState.AVAILABLE] with the given concrete [asset].
+  ///
+  /// It's an error to mark an already-available node as available. It should be
+  /// marked as dirty first.
+  void setAvailable(Asset asset) {
+    assert(asset.id == node.id);
+    assert(node._state != AssetState.REMOVED);
+    assert(node._state != AssetState.AVAILABLE);
+    node._state = AssetState.AVAILABLE;
+    node._asset = asset;
+    node._lazyCallback = null;
+    node._stateChangeController.add(AssetState.AVAILABLE);
+  }
+
+  /// Marks the node as [AssetState.RUNNING] and lazy.
+  ///
+  /// Lazy nodes aren't expected to have their values generated until needed.
+  /// Once it's necessary, [callback] will be called. [callback] is guaranteed
+  /// to be called only once.
+  ///
+  /// See also [AssetNodeController.lazy].
+  void setLazy(void callback()) {
+    assert(node._state != AssetState.REMOVED);
+    node._state = AssetState.RUNNING;
+    node._asset = null;
+    node._lazyCallback = callback;
+    node._stateChangeController.add(AssetState.RUNNING);
+  }
+
+  String toString() => "controller for $node";
+}
+
+// TODO(nweiz): add an error state.
+/// An enum of states that an [AssetNode] can be in.
+class AssetState {
+  /// The node has a concrete asset loaded, available, and up-to-date. The asset
+  /// is accessible via [AssetNode.asset]. An asset can only be marked available
+  /// again from the [AssetState.RUNNING] state.
+  static final AVAILABLE = const AssetState._("available");
+
+  /// The asset is no longer available, possibly for good. A removed asset will
+  /// never enter another state.
+  static final REMOVED = const AssetState._("removed");
+
+  /// The asset will exist in the future (unless it's removed), but the concrete
+  /// asset is not yet available.
+  static final RUNNING = const AssetState._("dirty");
+
+  /// Whether this state is [AssetState.AVAILABLE].
+  bool get isAvailable => this == AssetState.AVAILABLE;
+
+  /// Whether this state is [AssetState.REMOVED].
+  bool get isRemoved => this == AssetState.REMOVED;
+
+  /// Whether this state is [AssetState.RUNNING].
+  bool get isDirty => this == AssetState.RUNNING;
+
+  final String name;
+
+  const AssetState._(this.name);
+
+  String toString() => name;
+}