SeanFeldman / AsyncFriendlyStackTrace

Async-friendly format for stack traces and exceptions

Async-Friendly Stack Trace

Async-friendly format for stack traces and exceptions.

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.

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).
• 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.