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https://github.com/benaadams/Ben.Demystifier

High performance understanding for stack traces (Make error logs more productive)
https://github.com/benaadams/Ben.Demystifier

aspnet-core dotnet dotnet-core error-handling error-messages exceptions stack-traces

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High performance understanding for stack traces (Make error logs more productive)

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# Ben.Demystifier
[![NuGet version (Ben.Demystifier)](https://img.shields.io/nuget/v/Ben.Demystifier.svg?style=flat-square)](https://www.nuget.org/packages/Ben.Demystifier/)
[![build](https://github.com/benaadams/Ben.Demystifier/workflows/Demystifier%20PR%20Build/badge.svg)](https://github.com/benaadams/Ben.Demystifier/actions)

Output the modern C# 7.0+ features in stack traces that looks like the C# source code that generated them rather than IL formatted.

## High performance understanding for stack traces

.NET stack traces output the compiler transformed methods; rather than the source code methods, which make them slow to mentally parse and match back to the source code.

The current output was good for C# 1.0; but has become progressively worse since C# 2.0 (iterators, generics) as new features are added to the .NET languages and at C# 7.1 the stack traces are esoteric (see: [Problems with current stack traces](#problems-with-current-stack-traces)).

### Make error logs more productive

Output the modern C# 7.0+ features in stack traces in an understandable fashion that looks like the C# source code that generated them.

[![Demystified stacktrace](https://aoa.blob.core.windows.net/aspnet/stacktrace-demystified.png)](https://aoa.blob.core.windows.net/aspnet/stacktrace-demystified.png)

### Usage

```
exception.Demystify()
```
Or instead of Environment.StackTrace
```
EnhancedStackTrace.Current()
```
Resolves the stack back to the C# source format of the calls (and is an inspectable list of stack frames)

Calling `.ToString()` on the Demystified exception will produce a string stacktrace similar to the following (without the comments):

```csharp
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at bool System.Collections.Generic.List+Enumerator.MoveNextRare()
at IEnumerable Program.Iterator(int startAt)+MoveNext() // Resolved enumerator
at bool System.Linq.Enumerable+SelectEnumerableIterator.MoveNext() // Resolved enumerator
at string string.Join(string separator, IEnumerable values)
at string Program+GenericClass.GenericMethod(ref TSubType value)
at async Task Program.MethodAsync(int value) // Resolved async
at async Task Program.MethodAsync(TValue value) // Resolved async
at string Program.Method(string value)+()=>{} [0] // lambda source + ordinal
at string Program.Method(string value)+()=>{} [1] // lambda source + ordinal
at string Program.RunLambda(Func lambda)
at (string val, bool) Program.Method(string value) // Tuple returning
at ref string Program.RefMethod(in string value)+LocalFuncRefReturn() // ref return local func
at int Program.RefMethod(in string value)+LocalFuncParam(string val) // local function
at string Program.RefMethod(in string value) // in param (readonly ref)
at (string val, bool) static Program()+(string s, bool b)=>{} // tuple return static lambda
at void static Program()+(string s, bool b)=>{} // void static lambda
at void Program.Start((string val, bool) param) // Resolved tuple param
at void Program.Start((string val, bool) param)+LocalFunc1(long l) // void local function
at bool Program.Start((string val, bool) param)+LocalFunc2(bool b1, bool b2) // bool return local function
at string Program.Start()
at void Program()+()=>{} // ctor defined lambda
at void Program(Action action)+(object state)=>{} // ctor defined lambda
at void Program.RunAction(Action lambda, object state)
at new Program(Action action) // constructor
at new Program() // constructor
at void Program.Main(String[] args)
```

Calling `.ToString()` on the same exception would produce the following output

```csharp
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion() // ? low value
at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
at Program.d__3.MoveNext() // which enumerator?
at System.Linq.Enumerable.SelectEnumerableIterator`2.MoveNext() // which enumerator?
at System.String.Join(String separator, IEnumerable`1 values)
at Program.GenericClass`1.GenericMethod[TSubType](TSubType& value)
at Program.d__4.MoveNext() // which async overload?
--- End of stack trace from previous location where exception was thrown --- // ? no value
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() // ? no value
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) // ? no value
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() // ? no value
at Program.d__5`1.MoveNext() // which async overload?
--- End of stack trace from previous location where exception was thrown --- // ? no value
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() // ? no value
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) // ? no value
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() // ? no value
at Program.<>c__DisplayClass8_0.b__0() // ¯\_(ツ)_/¯
at Program.<>c__DisplayClass8_0.b__1() // ¯\_(ツ)_/¯
at Program.RunLambda(Func`1 lambda)
at Program.Method(String value)
at Program.g__LocalFuncRefReturn|10_1(<>c__DisplayClass10_0& ) // local function
at Program.g__LocalFuncParam|10_0(String val, <>c__DisplayClass10_0& ) // local function
at Program.RefMethod(String value)
at Program.<>c.<.cctor>b__18_1(String s, Boolean b) // ¯\_(ツ)_/¯
at Program.<>c.<.cctor>b__18_0(String s, Boolean b) // ¯\_(ツ)_/¯
at Program.Start(ValueTuple`2 param) // Tuple param?
at Program.g__LocalFunc1|11_0(Int64 l) // local function
at Program.g__LocalFunc2|11_1(Boolean b1, Boolean b2) // local function
at Program.Start()
at Program.<>c.<.ctor>b__1_0() // ¯\_(ツ)_/¯
at Program.<>c__DisplayClass2_0.<.ctor>b__0(Object state) // ¯\_(ツ)_/¯
at Program.RunAction(Action`1 lambda, Object state)
at Program..ctor(Action action) // constructor
at Program..ctor() // constructor
at Program.Main(String[] args)
```
Which is far less helpful, and close to jibberish in places

### Problems with current stack traces:

* **constructors**

Does not match code, output as `.ctor` and `.cctor`

* **parameters**

Do not specify qualifier `ref`, `out` or `in`

* **iterators**

Cannot determine overload `d__3.MoveNext()` rather than `Iterator(int startAt)+MoveNext()`
* **Linq**

Cannot determine overload

`Linq.Enumerable.SelectEnumerableIterator``2.MoveNext()`

rather than

`Linq.Enumerable+SelectEnumerableIterator.MoveNext()`
* **async**

Cannot determine overload and no modifier such as `async`

`d__5``1.MoveNext()`

rather than

`async Task Program.MethodAsync(int value)`

Noise!
```
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
```

* **lambdas**

Mostly jibberish `<>c__DisplayClass2_0.<.ctor>b__0(Object state)` with a suggestion of where they are declared but no hint if there are multiple overloads of the method.
* **local functions**

Mostly jibberish `g__LocalFuncParam|10_0(String val, <>c__DisplayClass10_0& )` with a suggestion of where they are declared but no hint if there are multiple overloads of the method.

* **generic parameters**

Not resolved, only an indication of the number `RunLambda(Func``1 lambda)` rather than `RunLambda(Func lambda)`
* **value tuples**

Do not match code, output as `ValueTuple``2 param` rather than `(string val, bool) param`
* **primitive types**

Do not match code, output as `Int64`, `Boolean`, `String` rather than `long`, `bool`, `string`
* **return types**

Skipped entirely from method signature

### Benchmarks

To run benchmarks from the repository root:
```
dotnet run -p .\test\Ben.Demystifier.Benchmarks\ -c Release -f netcoreapp2.0 All
```
Note: we're only kicking off via `netcoreapp2.0`, benchmarks will run for all configured platforms like `net462`.