Add a stack chain class to the stack trace package.

pkg/stack_trace/lib/src/stack_zone_specification.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 stack_trace.stack_zone_specification;
+
+import 'dart:async';
+
+import 'trace.dart';
+import 'chain.dart';
+
+/// A class encapsulating the zone specification for a [Chain.capture] zone.
+///
+/// Until they're materialized and exposed to the user, stack chains are tracked
+/// as linked lists of [Trace]s using the [_Node] class. These nodes are stored
+/// in three distinct ways:
+///
+/// * When a callback is registered, a node is created and stored as a captured
+///   local variable until the callback is run.
+///
+/// * When a callback is run, its captured node is set as the [_currentNode] so
+///   it can be available to [Chain.current] and to be linked into additional
+///   chains when more callbacks are scheduled.
+///
+/// * When a callback throws an error or a [Chain.track]ed Future or Stream
+///   emits an error, the current node is associated with that error's stack
+///   trace using the [_chains] expando.
+///
+/// Since [ZoneSpecification] can't be extended or even implemented, in order to
+/// get a real [ZoneSpecification] instance it's necessary to call [toSpec].
+class StackZoneSpecification {
+  /// The expando that associates stack chains with [StackTrace]s.
+  ///
+  /// The chains are associated with stack traces rather than errors themselves
+  /// because it's a common practice to throw strings as errors, which can't be
+  /// used with expandos.
+  ///
+  /// The chain associated with a given stack trace doesn't contain a node for
+  /// that stack trace.
+  final _chains = new Expando<_Node>("stack chains");
+
+  /// The error handler for the zone.
+  ///
+  /// If this is null, that indicates that any unhandled errors should be passed
+  /// to the parent zone.
+  final ChainHandler _onError;
+
+  /// The most recent node of the current stack chain.
+  _Node _currentNode;
+
+  StackZoneSpecification([this._onError]);
+
+  /// Converts [this] to a real [ZoneSpecification].
+  ZoneSpecification toSpec() {
+    return new ZoneSpecification(
+        handleUncaughtError: handleUncaughtError,
+        registerCallback: registerCallback,
+        registerUnaryCallback: registerUnaryCallback,
+        registerBinaryCallback: registerBinaryCallback);
+  }
+
+  /// Returns the current stack chain.
+  ///
+  /// By default, the first frame of the first trace will be the line where
+  /// [currentChain] is called. If [level] is passed, the first trace will start
+  /// that many frames up instead.
+  Chain currentChain([int level=0]) => _createNode(level + 1).toChain();
+
+  /// Returns the stack chain associated with [trace], if one exists.
+  ///
+  /// The first stack trace in the returned chain will always be [trace]
+  /// (converted to a [Trace] if necessary). If there is no chain associated
+  /// with [trace], this just returns a single-trace chain containing [trace].
+  Chain chainFor(StackTrace trace) {
+    if (trace is Chain) return trace;
+    var previous = trace == null ? null : _chains[trace];
+    return new _Node(trace, previous).toChain();
+  }
+
+  /// Ensures that an error emitted by [future] has the correct stack
+  /// information associated with it.
+  ///
+  /// By default, the first frame of the first trace will be the line where
+  /// [trackFuture] is called. If [level] is passed, the first trace will start
+  /// that many frames up instead.
+  Future trackFuture(Future future, [int level=0]) {
+    var completer = new Completer.sync();
+    var node = _createNode(level + 1);
+    future.then(completer.complete).catchError((e, stackTrace) {
+      if (stackTrace == null) stackTrace = new Trace.current();
+      if (_chains[stackTrace] == null) _chains[stackTrace] = node;
+      completer.completeError(e, stackTrace);
+    });
+    return completer.future;
+  }
+
+  /// Ensures that any errors emitted by [stream] have the correct stack
+  /// information associated with them.
+  ///
+  /// By default, the first frame of the first trace will be the line where
+  /// [trackStream] is called. If [level] is passed, the first trace will start
+  /// that many frames up instead.
+  Stream trackStream(Stream stream, [int level=0]) {
+    var node = _createNode(level + 1);
+    return stream.transform(new StreamTransformer.fromHandlers(
+        handleError: (error, stackTrace, sink) {
+      if (stackTrace == null) stackTrace = new Trace.current();
+      if (_chains[stackTrace] == null) _chains[stackTrace] = node;
+      sink.addError(error, stackTrace);
+    }));
+  }
+
+  /// Tracks the current stack chain so it can be set to [_currentChain] when
+  /// [f] is run.
+  ZoneCallback registerCallback(Zone self, ZoneDelegate parent, Zone zone,
+      Function f) {
+    if (f == null) return parent.registerCallback(zone, null);
+    var node = _createNode(1);
+    return parent.registerCallback(zone, () => _run(f, node));
+  }
+
+  /// Tracks the current stack chain so it can be set to [_currentChain] when
+  /// [f] is run.
+  ZoneUnaryCallback registerUnaryCallback(Zone self, ZoneDelegate parent,
+      Zone zone, Function f) {
+    if (f == null) return parent.registerUnaryCallback(zone, null);
+    var node = _createNode(1);
+    return parent.registerUnaryCallback(zone, (arg) {
+      return _run(() => f(arg), node);
+    });
+  }
+
+  /// Tracks the current stack chain so it can be set to [_currentChain] when
+  /// [f] is run.
+  ZoneBinaryCallback registerBinaryCallback(Zone self, ZoneDelegate parent,
+      Zone zone, Function f) {
+    if (f == null) return parent.registerBinaryCallback(zone, null);
+    var node = _createNode(1);
+    return parent.registerBinaryCallback(zone, (arg1, arg2) {
+      return _run(() => f(arg1, arg2), node);
+    });
+  }
+
+  /// Looks up the chain associated with [stackTrace] and passes it either to
+  /// [_onError] or [parent]'s error handler.
+  handleUncaughtError(Zone self, ZoneDelegate parent, Zone zone, error,
+      StackTrace stackTrace) {
+    if (_onError == null) {
+      return parent.handleUncaughtError(zone, error, chainFor(stackTrace));
+    } else {
+      _onError(error, chainFor(stackTrace));
+    }
+  }
+
+  /// Creates a [_Node] with the current stack trace and linked to
+  /// [_currentNode].
+  ///
+  /// By default, the first frame of the first trace will be the line where
+  /// [_createNode] is called. If [level] is passed, the first trace will start
+  /// that many frames up instead.
+  _Node _createNode([int level=0]) =>
+    new _Node(new Trace.current(level + 1), _currentNode);
+
+  // TODO(nweiz): use a more robust way of detecting and tracking errors when
+  // issue 15105 is fixed.
+  /// Runs [f] with [_currentNode] set to [node].
+  ///
+  /// If [f] throws an error, this associates [node] with that error's stack
+  /// trace.
+  _run(Function f, _Node node) {
+    var previousNode = _currentNode;
+    _currentNode = node;
+    try {
+      return f();
+    } catch (e, stackTrace) {
+      _chains[stackTrace] = node;
+      rethrow;
+    } finally {
+      _currentNode = previousNode;
+    }
+  }
+}
+
+/// A linked list node representing a single entry in a stack chain.
+class _Node {
+  /// The stack trace for this link of the chain.
+  final Trace trace;
+
+  /// The previous node in the chain.
+  final _Node previous;
+
+  _Node(StackTrace trace, [this.previous])
+      : trace = trace == null ? new Trace.current() : new Trace.from(trace);
+
+  /// Converts this to a [Chain].
+  Chain toChain() {
+    var nodes = <Trace>[];
+    var node = this;
+    while (node != null) {
+      nodes.add(node.trace);
+      node = node.previous;
+    }
+    return new Chain(nodes);
+  }
+}