Support transforming the exception in Future.transform().

tests/corelib/future_test.dart

Index: tests/corelib/future_test.dart
diff --git a/tests/corelib/future_test.dart b/tests/corelib/future_test.dart
index b26ed40b6955e208418b8e1756fe6ff45bf3726e..d9a4bd5c7f180db5949882a62b86ecf1f3bd5f78 100644
--- a/tests/corelib/future_test.dart
+++ b/tests/corelib/future_test.dart
@@ -442,6 +442,78 @@ testTransformTransformerFails() {
   Expect.equals(error, transformedFuture.exception);
 }
 
+testTransformOnExceptionTransformerThrows() {
+  final completer = new Completer<String>();
+  var called = false;
+
+  final transformedFuture = completer.future.transform((x) {
+    throw "throw from transform";
+  }, (ex) {
+    Expect.equals("throw from transform", ex);
+    called = true;
+    throw "transformed error";
+  });
+
+  completer.complete("original error");

[Siggi Cherem (dart-lang), 2012/09/04 16:56:33]

original error => normal value?

+  Expect.isTrue(called);
+  Expect.isTrue(transformedFuture.isComplete);
+  Expect.equals("transformed error", transformedFuture.exception);
+}
+
+testTransformOnExceptionThrows() {
+  final completer = new Completer<String>();
+  var called = false;
+
+  final transformedFuture = completer.future.transform((x) {
+    Expect.fail("should not get here");
+  }, (ex) {
+    Expect.equals("original error", ex);
+    called = true;
+    throw "transformed error";
+  });
+
+  completer.completeException("original error");
+  Expect.isTrue(called);
+  Expect.isTrue(transformedFuture.isComplete);
+  Expect.equals("transformed error", transformedFuture.exception);
+}
+
+testTransformOnExceptionReturnsTrue() {
+  final completer = new Completer<String>();
+  var called = false;
+
+  final transformedFuture = completer.future.transform((x) {
+    Expect.fail("should not get here");
+  }, (ex) {
+    Expect.equals("original error", ex);
+    called = true;
+    return true;
+  });
+
+  completer.completeException("original error");
+  Expect.isTrue(called);
+  Expect.isFalse(transformedFuture.isComplete);
+}
+
+testTransformOnExceptionReturnsNontrue() {
+  final completer = new Completer<String>();
+  var called = false;
+
+  final transformedFuture = completer.future.transform((x) {
+    Expect.fail("should not get here");
+  }, (ex) {
+    Expect.equals("original error", ex);
+    called = true;
+    return null;
+  });
+
+  completer.completeException("original error");
+  Expect.isTrue(called);
+  Expect.isTrue(transformedFuture.isComplete);
+  Expect.equals("original error", transformedFuture.exception);
+}
+
+
 // Tests for Future.chain
 
 testChainSuccess() {
@@ -529,6 +601,10 @@ main() {
   testTransformSuccess();
   testTransformFutureFails();
   testTransformTransformerFails();
+  testTransformOnExceptionTransformerThrows();
+  testTransformOnExceptionThrows();
+  testTransformOnExceptionReturnsTrue();
+  testTransformOnExceptionReturnsNontrue();
   testChainSuccess();
   testChainFirstFutureFails();
   testChainTransformerFails();