Make exceptions propagate through multiple Future branches.

tests/corelib/future_test.dart

 // Copyright (c) 2012, 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.
 
 // Tests for Future.immediate
 
 testImmediate() {
   final future = new Future<String>.immediate("42");
   Expect.isTrue(future.isComplete);
   Expect.isTrue(future.hasValue);
@@ skipping 547 matching lines @@
 
   completer.completeException("original error");
   Expect.isTrue(called);
   Expect.isFalse(transformedFuture.isComplete);
 
   returnedCompleter.complete("transformed value");
   Expect.isTrue(transformedFuture.isComplete);
   Expect.equals("transformed value", transformedFuture.value);
 }
 
+// Tests for branching exceptions
+
+testExceptionTravelsAlongBothBranches() {
+  var results = <int>[];
+
+  var completer = new Completer();
+  var branch1 = completer.future.transform((_) => null);
+  var branch2 = completer.future.transform((_) => null);
+
+  branch1.handleException((e) {
+    results.add(1);
+    return true;
+  });
+
+  branch2.handleException((e) {
+    results.add(2);
+    return true;
+  });
+
+  completer.completeException("error");
+  Expect.listEquals([1, 2], results);
+}
+
+testExceptionTravelsAlongBothBranchesAfterComplete() {
+  var results = <int>[];
+
+  var completer = new Completer();
+  completer.completeException("error");
+
+  var branch1 = completer.future.transform((_) => null);
+  var branch2 = completer.future.transform((_) => null);
+
+  branch1.handleException((e) {
+    results.add(1);
+    return true;
+  });
+
+  branch2.handleException((e) {
+    results.add(2);
+    return true;
+  });
+
+  Expect.listEquals([2, 1], results);

[Siggi Cherem (dart-lang), 2012/11/21 01:08:57]

it's weird to see these in opposite order, maybe use Expect.setEquals so that we
test only the relevant part?

(same in all other places)

[nweiz, 2012/11/21 20:39:09]

Done.

+}
+
+testExceptionIsHandledInBaseAndBranch() {
+  var results = <String>[];
+
+  var completer = new Completer();
+  var branch = completer.future.transform((_) => null);
+
+  completer.future.handleException((e) {
+    results.add("base");
+    return true;
+  });
+
+  branch.handleException((e) {
+    results.add("branch");
+    return true;
+  });
+
+  completer.completeException("error");
+  Expect.listEquals(["branch", "base"], results);
+}
+
+testExceptionIsHandledInBaseAndBranchAfterComplete() {
+  var results = <String>[];
+
+  var completer = new Completer();
+  completer.completeException("error");
+
+  var branch = completer.future.transform((_) => null);

[Siggi Cherem (dart-lang), 2012/11/21 01:08:57]

maybe add another test to check what happens if you do the transform after
adding 'handleException'? That is,

var base = completer.future;
base.handleException((e) { results.add('base'); return true; });
var branch = base.transform((_) => null);
...

[nweiz, 2012/11/21 20:39:09]

That case isn't handled by this CL; it will actually stop the exception from
propagating. The correct behavior in that situation is a little less clear-cut.

+
+  completer.future.handleException((e) {
+    results.add("base");
+    return true;
+  });
+
+  branch.handleException((e) {
+    results.add("branch");
+    return true;
+  });
+
+  Expect.listEquals(["base", "branch"], results);
+}
+
 main() {
   testImmediate();
   testNeverComplete();
   testComplete();
   testCompleteWithCompleteHandlerBeforeComplete();
   testExceptionWithCompleteHandlerBeforeComplete();
   testCompleteWithCompleteHandlerAfterComplete();
   testExceptionWithCompleteHandlerAfterComplete();
   testCompleteWithManyCompleteHandlers();
   testExceptionWithManyCompleteHandlers();
@@ skipping 20 matching lines @@
   testTransformFutureFails();
   testTransformTransformerFails();
   testChainSuccess();
   testChainFirstFutureFails();
   testChainTransformerFails();
   testChainSecondFutureFails();
   testTransformExceptionCompletesNormally();
   testTransformExceptionThrows();
   testTransformExceptionReturns();
   testTransformExceptionReturnsAFuture();
+  testExceptionTravelsAlongBothBranches();
+  testExceptionIsHandledInBaseAndBranch();

[Siggi Cherem (dart-lang), 2012/11/21 01:08:57]

add the other 2 tests? (...AfterComplete)

[nweiz, 2012/11/21 20:39:09]

Done.

 }