From 3e2252d2ce81aed636649b8a84fae825c6be34ca Mon Sep 17 00:00:00 2001
From: Dennis Daume <daume.dennis@gmail.com>
Date: Wed, 30 Jul 2014 18:50:55 +0200
Subject: [PATCH 1/2] Make ExecuteAsync throw the original exception

This fixes #685
---
 ReactiveUI.Tests/ReactiveCommandTest.cs | 31 +++++++++++++++++++++++++
 ReactiveUI/ReactiveCommand.cs           |  4 ++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/ReactiveUI.Tests/ReactiveCommandTest.cs b/ReactiveUI.Tests/ReactiveCommandTest.cs
index a24c81a1e5..1a22473d30 100644
--- a/ReactiveUI.Tests/ReactiveCommandTest.cs
+++ b/ReactiveUI.Tests/ReactiveCommandTest.cs
@@ -180,6 +180,37 @@ public void NoSubscriberOfThrownExceptionsEqualsDeath()
                 Assert.False(failed);
             });
         }
+
+        [Fact]
+        public async Task ExecuteAsyncThrowsExceptionOnError()
+        {
+            var command = ReactiveCommand.CreateAsyncObservable(_ =>
+                Observable.Throw<Unit>(new Exception("Aieeeee!")));
+
+            var exceptions = command.ThrownExceptions.CreateCollection();
+
+            bool failed = false;
+            try {
+                await command.ExecuteAsync();
+            } catch (Exception ex) {
+                failed = ex.Message == "Aieeeee!";
+            }
+
+            Assert.True(failed);
+            Assert.Equal(1, exceptions.Count);
+            Assert.Equal("Aieeeee!", exceptions[0].Message);
+        }
+
+        [Fact]
+        public void ExecuteDoesntThrowOnError()
+        {
+            var command = ReactiveCommand.CreateAsyncObservable(_ =>
+            Observable.Throw<Unit>(new Exception("Aieeeee!")));
+
+            command.ThrownExceptions.Subscribe();
+
+            command.Execute(null);
+        }
     }
 
     public class ReactiveAsyncCommandTest
diff --git a/ReactiveUI/ReactiveCommand.cs b/ReactiveUI/ReactiveCommand.cs
index 412ed78e26..6bc199dd54 100644
--- a/ReactiveUI/ReactiveCommand.cs
+++ b/ReactiveUI/ReactiveCommand.cs
@@ -374,7 +374,7 @@ public IObservable<T> ExecuteAsync(object parameter = null)
                     .Do(x => executeResults.OnNext(x))
                     .Catch<T, Exception>(ex => {
                         exceptions.OnNext(ex);
-                        return Observable.Empty<T>();
+                        return Observable.Throw<T>(ex);
                     })
                     .Subscribe(subj);
 
@@ -446,7 +446,7 @@ public bool CanExecute(object parameter)
 
         public void Execute(object parameter)
         {
-            ExecuteAsync(parameter).Subscribe();
+            ExecuteAsync(parameter).Catch(Observable.Empty<T>()).Subscribe();
         }
 
         public void Dispose()

From 09ae483231360bf348b1eaec7f6e7a7ffe2743ab Mon Sep 17 00:00:00 2001
From: Dennis Daume <daume.dennis@gmail.com>
Date: Wed, 30 Jul 2014 19:35:36 +0200
Subject: [PATCH 2/2] Remove the Catch and OnNext the error on the Do method
 above

---
 ReactiveUI/ReactiveCommand.cs | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/ReactiveUI/ReactiveCommand.cs b/ReactiveUI/ReactiveCommand.cs
index 6bc199dd54..d92b6e3b45 100644
--- a/ReactiveUI/ReactiveCommand.cs
+++ b/ReactiveUI/ReactiveCommand.cs
@@ -371,11 +371,7 @@ public IObservable<T> ExecuteAsync(object parameter = null)
                 var disp = executeAsync(parameter)
                     .ObserveOn(scheduler)
                     .Finally(() => decrement.Disposable = Disposable.Empty)
-                    .Do(x => executeResults.OnNext(x))
-                    .Catch<T, Exception>(ex => {
-                        exceptions.OnNext(ex);
-                        return Observable.Throw<T>(ex);
-                    })
+                    .Do(x => executeResults.OnNext(x), ex => exceptions.OnNext(ex))
                     .Subscribe(subj);
 
                 return new CompositeDisposable(disp, decrement);