Async-Friendly Stack Trace

Async-friendly format for stack traces and exceptions.

Also check out Ben's Demystifier which resolves async, iterators, tuples, location functions and more.

System.Exception: Crash! Boom! Bang!
   at async AsyncFriendlyStackTrace.Test.Example1.C(?) in C:\Source\Repos\AsyncFriendlyStackTrace\src\AsyncFriendlyStackTrace.Test\Example1.cs:line 26
   at async AsyncFriendlyStackTrace.Test.Example1.B(?) in C:\Source\Repos\AsyncFriendlyStackTrace\src\AsyncFriendlyStackTrace.Test\Example1.cs:line 20
   at async AsyncFriendlyStackTrace.Test.Example1.A(?) in C:\Source\Repos\AsyncFriendlyStackTrace\src\AsyncFriendlyStackTrace.Test\Example1.cs:line 15
   at async AsyncFriendlyStackTrace.Test.Example1.Run(?) in C:\Source\Repos\AsyncFriendlyStackTrace\src\AsyncFriendlyStackTrace.Test\Example1.cs:line 10
   at AsyncFriendlyStackTrace.Test.Program.Run[TExample](TextWriter writer) in C:\Source\Repos\AsyncFriendlyStackTrace\src\AsyncFriendlyStackTrace.Test\Program.cs:line 45

Install

Install-Package AsyncFriendlyStackTrace

Usage

To format exceptions, use the extension methods in ExceptionExtensions:

exception.ToAsyncString();

This produces an async-friendly format, as you can see in the examples below. There is also special handling for AggregateExceptions and ReflectionTypeLoadException (which can contain multiple inner exceptions).

The main formatting work is done by the StackTraceExtensions.ToAsyncString extension method. The async-friendly formatting is archieved by:

• Skipping all awaiter frames (all methods in types implementing INotifyCompletion) and ExceptionDispatchInfo frames.
• Inferring the original method name from the async state machine class (IAsyncStateMachine) and removing the "MoveNext" - currently only for C#.
• Adding the "async" prefix after "at" on each line for async invocations.
• Appending "(?)" to the method signature to indicate that parameter information is missing.
• Removing the "End of stack trace from previous location..." text.

Example outputs

In all the examples, OLD refrers to ToString() output, while NEW is ToAsyncString().

• Example 1 (code): A simple 3 async method chain.
• Example 2 (code): Async invocations with a synchronous Wait() in the middle, causing an AggregateException.
• Example 3 (code): Bad Serialization - When exception is serialized and deserialized, its stack trace is saved as string. So we can't reformat the stack trace. The "new" stack trace is still a bit shorter due to an improved AggregateException formatting (the first inner exception isn't repeated twice).
• Example 4 (code): Good Serialization - We use the PrepareForAsyncSerialization before serializing the exception. This saves the async-friendly stack trace as a string in the Data dictionary of the exception. This has two downsides:
  • The serialized data will now contain both stack trace formats.
  • When using the DataContractSerializer, you must include exception.Data.GetType() as a known type. This is because its concrete type (ListDictionaryInternal) is internal.