feat(errors): preserve stack traces of user exceptions in Dart

modules/angular2/test/facade/async_dart_spec.dart

@@ -0,0 +1,100 @@
+/// This file contains tests that make sense only in Dart
+library angular2.test.facade.async_dart_spec;
+
+import 'package:angular2/test_lib.dart';
+import 'package:angular2/src/facade/async.dart';
+
+class MockException implements Error { var message; var stackTrace; }
+
+void functionThatThrows() {
+  try { throw new MockException(); }
+  catch(e, stack) {
+    // If we lose the stack trace the message will no longer match
+    // the first line in the stack
+    e.message = stack.toString().split('\n')[0];
+    e.stackTrace = stack;
+    rethrow;
+  }
+}
+
+void functionThatThrowsNonError() {
+  throw 'this is an error';
+}
+
+void expectFunctionThatThrowsWithStackTrace(
+    Future future, AsyncTestCompleter async) {
+  PromiseWrapper.catchError(future, (err, StackTrace stack) {
+    expect(stack.toString().split('\n')[0]).toEqual(err.message);
+    async.done();
+  });
+}
+
+void expectFunctionThatThrowsWithoutStackTrace(Future future,
+    AsyncTestCompleter async) {
+  PromiseWrapper.catchError(future, (err, StackTrace stack) {
+    expect(stack).toBe(null);
+    async.done();
+  });
+}
+
+main() {
+  describe('Completer', () {
+
+    it('should preserve error stack traces',
+        inject([AsyncTestCompleter], (async) {
+      var c = PromiseWrapper.completer();
+
+      expectFunctionThatThrowsWithStackTrace(c.promise, async);
+
+      try {
+        functionThatThrows();
+      } catch(e) {
+        c.reject(e);
+      }
+    }));
+
+    // TODO: We might fix this one day; for now testing it to be explicit
+    it('CANNOT preserve error stack traces for non-Errors',
+        inject([AsyncTestCompleter], (async) {
+      var c = PromiseWrapper.completer();
+
+      expectFunctionThatThrowsWithoutStackTrace(c.promise, async);
+
+      try {
+        functionThatThrowsNonError();
+      } catch(e) {
+        c.reject(e);
+      }
+    }));
+
+  });
+
+  describe('PromiseWrapper', () {
+
+    describe('reject', () {
+
+      it('should preserve error stack traces',
+          inject([AsyncTestCompleter], (async) {
+        try {
+          functionThatThrows();
+        } catch(e) {
+          var rejectedFuture = PromiseWrapper.reject(e);
+          expectFunctionThatThrowsWithStackTrace(rejectedFuture, async);
+        }
+      }));
+
+      // TODO: We might fix this one day; for now testing it to be explicit
+      it('CANNOT preserve stack traces for non-Errors',
+          inject([AsyncTestCompleter], (async) {
+        try {
+          functionThatThrowsNonError();
+        } catch(e) {
+          var rejectedFuture = PromiseWrapper.reject(e);
+          expectFunctionThatThrowsWithoutStackTrace(rejectedFuture, async);
+        }
+      }));
+
+    });
+
+  });
+}