Refactor groups to pipe them through to the runner.

lib/src/backend/declarer.dart

Index: lib/src/backend/declarer.dart
diff --git a/lib/src/backend/declarer.dart b/lib/src/backend/declarer.dart
index df2ec06ee47b600e9a1b9a5baad65a326091e43f..a3c201172575148630e887c3a9529e9dcc2e7961 100644
--- a/lib/src/backend/declarer.dart
+++ b/lib/src/backend/declarer.dart
@@ -4,41 +4,76 @@
 
 library test.backend.declarer;
 
-import 'dart:collection';
+import 'dart:async';
 
 import '../frontend/timeout.dart';
+import '../utils.dart';
 import 'group.dart';
 import 'invoker.dart';
 import 'metadata.dart';
-import 'test.dart';
+import 'suite_entry.dart';
 
 /// A class that manages the state of tests as they're declared.
 ///
-/// This is in charge of tracking the current group, set-up, and tear-down
-/// functions. It produces a list of runnable [tests].
+/// A nested tree of Declarers tracks the current group, set-up, and tear-down
+/// functions. Each Declarer in the tree corresponds to a group. This tree is
+/// tracked by a zone-scoped "current" Declarer; the current declarer can be set
+/// for a block using [Declarer.declare], and it can be accessed using
+/// [Declarer.current].
 class Declarer {
-  /// The current group.
-  var _group = new Group.root();
+  /// The parent declarer, or `null` if this corresponds to the root group.
+  final Declarer _parent;
 
-  /// The list of tests that have been defined.
-  List<Test> get tests => new UnmodifiableListView<Test>(_tests);
-  final _tests = new List<Test>();
+  /// The name of the current test group, including the name of any parent
+  /// groups.
+  ///
+  /// This is `null` if this is the root group.
+  final String _name;
 
-  Declarer();
+  /// The metadata for this group, including the metadata of any parent groups
+  /// and of the test suite.
+  final Metadata _metadata;
 
-  /// Defines a test case with the given description and body.
-  void test(String description, body(), {String testOn, Timeout timeout,
-      skip, Map<String, dynamic> onPlatform}) {
-    // TODO(nweiz): Once tests have begun running, throw an error if [test] is
-    // called.
-    var prefix = _group.description;
-    if (prefix != null) description = "$prefix $description";
+  /// The set-up functions for this group.
+  final _setUps = new List<AsyncFunction>();
 
-    var metadata = _group.metadata.merge(new Metadata.parse(
+  /// The tear-down functions for this group.
+  final _tearDowns = new List<AsyncFunction>();
+
+  /// The children of this group, either tests or sub-groups.
+  final _entries = new List<SuiteEntry>();
+
+  /// Whether [build] has been called for this declarer.
+  bool _built = false;
+
+  /// The current zone-scoped declarer.
+  static Declarer get current => Zone.current[#test.declarer];
+
+  /// Creates a new declarer for the root group.
+  ///
+  /// This is the implicit group that exists outside of any calls to `group()`.
+  /// [metadata] should be the suite's metadata, if available.
+  Declarer([Metadata metadata])
+      : this._(null, null, metadata == null ? new Metadata() : metadata);
+
+  Declarer._(this._parent, this._name, this._metadata);
+
+  /// Runs [body] with this declarer as [Declarer.current].
+  ///
+  /// Returns the return value of [body].
+  declare(body()) => runZoned(body, zoneValues: {#test.declarer: this});
+
+  /// Defines a test case with the given name and body.
+  void test(String name, body(), {String testOn, Timeout timeout, skip,
+      Map<String, dynamic> onPlatform}) {
+    if (_built) {
+      throw new StateError("Can't call test() once tests have begun running.");
+    }
+
+    var metadata = _metadata.merge(new Metadata.parse(
         testOn: testOn, timeout: timeout, skip: skip, onPlatform: onPlatform));
 
-    var group = _group;
-    _tests.add(new LocalTest(description, metadata, () {
+    _entries.add(new LocalTest(_prefix(name), metadata, () {
       // TODO(nweiz): It might be useful to throw an error here if a test starts
       // running while other tests from the same declarer are also running,
       // since they might share closurized state.
@@ -46,40 +81,110 @@ class Declarer {
       // TODO(nweiz): Use async/await here once issue 23497 has been fixed in
       // two stable versions.
       return Invoker.current.waitForOutstandingCallbacks(() {
-        return group.runSetUps().then((_) => body());
-      }).then((_) => group.runTearDowns());
+        return _runSetUps().then((_) => body());
+      }).then((_) => _runTearDowns());
     }));
   }
 
   /// Creates a group of tests.
-  void group(String description, void body(), {String testOn,
-      Timeout timeout, skip, Map<String, dynamic> onPlatform}) {
-    var oldGroup = _group;
+  void group(String name, void body(), {String testOn, Timeout timeout, skip,
+      Map<String, dynamic> onPlatform}) {
+    if (_built) {
+      throw new StateError("Can't call group() once tests have begun running.");
+    }
 
-    var metadata = new Metadata.parse(
-        testOn: testOn, timeout: timeout, skip: skip, onPlatform: onPlatform);
+    var metadata = _metadata.merge(new Metadata.parse(
+        testOn: testOn, timeout: timeout, skip: skip, onPlatform: onPlatform));
 
-    // Don' load the tests for a skipped group.
+    // Don't load the tests for a skipped group.
     if (metadata.skip) {
-      _tests.add(new LocalTest(description, metadata, () {}));
+      _entries.add(new Group(name, metadata, []));
       return;
     }
 
-    _group = new Group(oldGroup, description, metadata);
-    try {
-      body();
-    } finally {
-      _group = oldGroup;
-    }
+    var declarer = new Declarer._(this, _prefix(name), metadata);
+    declarer.declare(body);
+    _entries.add(new Group(declarer._name, metadata, declarer.build()));
   }
 
-  /// Registers a function to be run before tests.
+  /// Returns [name] prefixed with this declarer's group name.
+  String _prefix(String name) => _name == null ? name : "$_name $name";
+
+  /// Registers a function to be run before each test in this group.
   void setUp(callback()) {
-    _group.setUps.add(callback);
+    if (_built) {
+      throw new StateError("Can't call setUp() once tests have begun running.");
+    }
+
+    _setUps.add(callback);
   }
 
-  /// Registers a function to be run after tests.
+  /// Registers a function to be run after each test in this group.
   void tearDown(callback()) {
-    _group.tearDowns.add(callback);
+    if (_built) {
+      throw new StateError(
+          "Can't call tearDown() once tests have begun running.");
+    }
+
+    _tearDowns.add(callback);
+  }
+
+  /// Finalizes and returns the tests and groups being declared.
+  List<SuiteEntry> build() {
+    if (_built) {
+      throw new StateError("Can't call Declarer.build() more than once.");
+    }
+
+    _built = true;
+    return _entries.toList();
+  }
+
+  /// Run the set-up functions for this and any parent groups.
+  ///
+  /// If no set-up functions are declared, this returns a [Future] that
+  /// completes immediately.
+  Future _runSetUps() {
+    // TODO(nweiz): Use async/await here once issue 23497 has been fixed in two
+    // stable versions.
+    if (_parent != null) {
+      return _parent._runSetUps().then((_) {
+        return Future.forEach(_setUps, (setUp) => setUp());
+      });
+    }
+
+    return Future.forEach(_setUps, (setUp) => setUp());
+  }
+
+  /// Run the tear-up functions for this and any parent groups.
+  ///
+  /// If no set-up functions are declared, this returns a [Future] that
+  /// completes immediately.
+  ///
+  /// This should only be called within a test.
+  Future _runTearDowns() {
+    return Invoker.current.unclosable(() {
+      var tearDowns = [];
+      for (var declarer = this; declarer != null; declarer = declarer._parent) {
+        tearDowns.addAll(declarer._tearDowns.reversed);
+      }
+
+      return Future.forEach(tearDowns, _errorsDontStopTest);
+    });
+  }
+
+  /// Runs [body] with special error-handling behavior.
+  ///
+  /// Errors emitted [body] will still cause the current test to fail, but they
+  /// won't cause it to *stop*. In particular, they won't remove any outstanding
+  /// callbacks registered outside of [body].
+  Future _errorsDontStopTest(body()) {
+    var completer = new Completer();
+
+    Invoker.current.addOutstandingCallback();
+    Invoker.current.waitForOutstandingCallbacks(() {
+      new Future.sync(body).whenComplete(completer.complete);
+    }).then((_) => Invoker.current.removeOutstandingCallback());
+
+    return completer.future;
   }
 }