Crash after compile error

[wasdfra]

During execution, the runner catches a compile error and ends up crashing. Had updated Stryker .NET to the most recent version just before (4.14.0)

Logs (removed file path)

[15:29:43 DBG] RollBacking mutations from <filepath>.
[15:29:43 WRN] An unidentified mutation in <filepath> resulted in a compile error (at 369:50) with id: CS0023, message: Operator '.' cannot be applied to operand of type 'void' (Source code: actionGroupName.Split('.')
                                                  .Reverse()
                                                  .Skip)
[15:29:43 INF] Safe Mode! Stryker will remove all mutations in DeeActionCode and mark them as 'compile error'.
[15:29:43 FTL] Stryker.NET could not compile the project after mutation. This is probably an error for Stryker.NET and not your project. Please report this issue on github with the previous error message.      
[15:29:43 ERR] An error occurred during the mutation test run 
System.AggregateException: One or more errors occurred. (Internal error due to compile error.)
 ---> Stryker.Abstractions.Exceptions.CompilationException: Internal error due to compile error.
   at Stryker.Core.Compiling.CSharpRollbackProcess.Start(CSharpCompilation compiler, ImmutableArray`1 diagnostics, Boolean lastAttempt, Boolean devMode) in /_/src/Stryker.Core/Stryker.Core/Compiling/CSharpRollbackProcess.cs:line 75
   at Stryker.Core.Compiling.CsharpCompilingProcess.TryCompilation(Stream ms, Stream symbolStream, CSharpCompilation& compilation, EmitResult previousEmitResult, Boolean lastAttempt, Int32 retryCount) in /_/src/Stryker.Core/Stryker.Core/Compiling/CsharpCompilingProcess.cs:line 186
   at Stryker.Core.Compiling.CsharpCompilingProcess.Compile(IEnumerable`1 syntaxTrees, Stream ilStream, Stream symbolStream) in /_/src/Stryker.Core/Stryker.Core/Compiling/CsharpCompilingProcess.cs:line 83      
   at Stryker.Core.MutationTest.CsharpMutationProcess.CompileMutations(MutationTestInput input, CsharpCompilingProcess compilingProcess) in /_/src/Stryker.Core/Stryker.Core/MutationTest/CsharpMutationProcess.cs:line 71
   at Stryker.Core.MutationTest.CsharpMutationProcess.Mutate(MutationTestInput input, IStrykerOptions options) in /_/src/Stryker.Core/Stryker.Core/MutationTest/CsharpMutationProcess.cs:line 61
   at Stryker.Core.MutationTest.MutationTestProcess.Mutate() in /_/src/Stryker.Core/Stryker.Core/MutationTest/MutationTestProcess.cs:line 65
   at Stryker.Core.Initialisation.ProjectMutator.MutateProject(IStrykerOptions options, MutationTestInput input, IReporter reporters, IMutationTestProcess mutationTestProcess) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectMutator.cs:line 39
   at Stryker.Core.Initialisation.ProjectOrchestrator.<>c__DisplayClass8_0.<MutateProjectsAsync>b__0(MutationTestInput mutationTestInput) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectOrchestrator.cs:line 76
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
   at System.Threading.Tasks.TaskReplicator.Replica.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.TaskReplicator.Run[TState](ReplicatableUserAction`1 action, ParallelOptions options, Boolean stopOnFirstFailure)
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
   at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable`1 source, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Action`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithEverything, Func`1 localInit, Action`1 localFinally)
   at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable`1 source, Action`1 body)
   at Stryker.Core.Initialisation.ProjectOrchestrator.MutateProjectsAsync(IStrykerOptions options, IReporter reporters, ITestRunner runner) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectOrchestrator.cs:line 74
   at Stryker.Core.StrykerRunner.RunMutationTestAsync(IStrykerInputs inputs) in /_/src/Stryker.Core/Stryker.Core/StrykerRunner.cs:line 61
[15:29:43 INF] Time Elapsed 00:10:27.8328658
Unhandled exception. System.AggregateException: One or more errors occurred. (Internal error due to compile error.)
 ---> Stryker.Abstractions.Exceptions.CompilationException: Internal error due to compile error.
   at Stryker.Core.Compiling.CSharpRollbackProcess.Start(CSharpCompilation compiler, ImmutableArray`1 diagnostics, Boolean lastAttempt, Boolean devMode) in /_/src/Stryker.Core/Stryker.Core/Compiling/CSharpRollbackProcess.cs:line 75
   at Stryker.Core.Compiling.CsharpCompilingProcess.TryCompilation(Stream ms, Stream symbolStream, CSharpCompilation& compilation, EmitResult previousEmitResult, Boolean lastAttempt, Int32 retryCount) in /_/src/Stryker.Core/Stryker.Core/Compiling/CsharpCompilingProcess.cs:line 186
   at Stryker.Core.Compiling.CsharpCompilingProcess.Compile(IEnumerable`1 syntaxTrees, Stream ilStream, Stream symbolStream) in /_/src/Stryker.Core/Stryker.Core/Compiling/CsharpCompilingProcess.cs:line 83      
   at Stryker.Core.MutationTest.CsharpMutationProcess.CompileMutations(MutationTestInput input, CsharpCompilingProcess compilingProcess) in /_/src/Stryker.Core/Stryker.Core/MutationTest/CsharpMutationProcess.cs:line 71
   at Stryker.Core.MutationTest.CsharpMutationProcess.Mutate(MutationTestInput input, IStrykerOptions options) in /_/src/Stryker.Core/Stryker.Core/MutationTest/CsharpMutationProcess.cs:line 61
   at Stryker.Core.MutationTest.MutationTestProcess.Mutate() in /_/src/Stryker.Core/Stryker.Core/MutationTest/MutationTestProcess.cs:line 65
   at Stryker.Core.Initialisation.ProjectMutator.MutateProject(IStrykerOptions options, MutationTestInput input, IReporter reporters, IMutationTestProcess mutationTestProcess) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectMutator.cs:line 39
   at Stryker.Core.Initialisation.ProjectOrchestrator.<>c__DisplayClass8_0.<MutateProjectsAsync>b__0(MutationTestInput mutationTestInput) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectOrchestrator.cs:line 76
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.<>c__DisplayClass19_0`2.<ForWorker>b__1(RangeWorker& currentWorker, Int64 timeout, Boolean& replicationDelegateYieldedBeforeCompletion)
   at System.Threading.Tasks.TaskReplicator.Replica.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.TaskReplicator.Run[TState](ReplicatableUserAction`1 action, ParallelOptions options, Boolean stopOnFirstFailure)
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Parallel.ForWorker[TLocal,TInt](TInt fromInclusive, TInt toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)
   at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable`1 source, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Action`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithEverything, Func`1 localInit, Action`1 localFinally)
   at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable`1 source, Action`1 body)
   at Stryker.Core.Initialisation.ProjectOrchestrator.MutateProjectsAsync(IStrykerOptions options, IReporter reporters, ITestRunner runner) in /_/src/Stryker.Core/Stryker.Core/Initialisation/ProjectOrchestrator.cs:line 74
   at Stryker.Core.StrykerRunner.RunMutationTestAsync(IStrykerInputs inputs) in /_/src/Stryker.Core/Stryker.Core/StrykerRunner.cs:line 61
   at Stryker.CLI.StrykerCli.RunStrykerAsync(IStrykerInputs inputs) in /_/src/Stryker.CLI/Stryker.CLI/StrykerCLI.cs:line 156
   at Stryker.CLI.StrykerCli.<>c__DisplayClass11_0.<<RunAsync>b__0>d.MoveNext() in /_/src/Stryker.CLI/Stryker.CLI/StrykerCLI.cs:line 128
--- End of stack trace from previous location ---
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.ExecuteAsync(String[] args, CancellationToken cancellationToken)
   at Stryker.CLI.StrykerCli.RunAsync(String[] args) in /_/src/Stryker.CLI/Stryker.CLI/StrykerCLI.cs:line 134
   at Stryker.CLI.Program.Main(String[] args) in /_/src/Stryker.CLI/Stryker.CLI/Program.cs:line 28
   at Stryker.CLI.Program.<Main>(String[] args)

Expected behavior
Expected the application not to crash

Desktop (please complete the following information):

• OS: Windows 11
• Type of project .net Core
• Framework Version .net Core 8
• Stryker Version 4.14.0

[dupdob]

thanks for opening this issue and sorry for your problem.
Any chance you could share the full log file (privately if needed) ? the warnings preceding the compilation error do not explain the problem.

[wasdfra]

Hello! Thank for the reply. Currently asking permission to see if I can share the full logs, as they contain customer code.

But in the meantime, the logs preceding the ones I've previously shared are for another cs file, and are as follows:

[15:29:43 DBG] RollBacking mutations from <filepath>.
[15:29:43 DBG] Found mutant 97151 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97152 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97150 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97154 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97155 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97153 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97157 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97158 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97156 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97160 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97161 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97159 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97162 of type 'CollectionExpression' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97167 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97169 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97171 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97172 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97174 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97175 of type 'Linq' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97176 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97178 of type 'CollectionExpression' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97179 of type 'CollectionExpression' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97180 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97182 of type 'Linq' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97183 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97185 of type 'CollectionExpression' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97186 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97188 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97190 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97191 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97194 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97198 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97199 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97200 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97201 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97196 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97197 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97203 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97207 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97206 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97208 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97205 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97204 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97210 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97212 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97213 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97218 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97221 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97222 of type 'Boolean' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97215 of type 'Boolean' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97225 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97224 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97228 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97229 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97227 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97232 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97233 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97231 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97236 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97235 of type 'Initializer' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 DBG] Found mutant 97239 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97240 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97241 of type 'String' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97242 of type 'Statement' controlled by 'IfInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97246 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97247 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97248 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97245 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97250 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97251 of type 'Equality' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant 97244 of type 'Logical' controlled by 'ConditionalInstrumentationEngine'.
[15:29:43 DBG] Found mutant -1 of type 'null' controlled by 'EndingReturnEngine'.
[15:29:43 WRN] An unidentified mutation in <filepath> resulted in a compile error (at 186:24) with id: CS0165, message: Use of unassigned local variable 'toSubstrateType' (Source code: toSubstrateType)
[15:29:43 INF] Safe Mode! Stryker will remove all mutations in DeeActionCode and mark them as 'compile error'.
[15:29:43 VRB] RolledBack to <original code>

To note that due to limitations on our system we extensively use local functions. Not sure if it may have an impact here

[wasdfra]

To add more information. Had a friend with an outdated version, 4.6.0, and he was able to run. After downgrading I was too able to run past this error, but still having issues with the latest (last try with the 4.14.0).

To note, this is without setting the stryker-config.json as well.

[dupdob]

thanks for the comment. here is my analysis of the problem:

Symptom

Stryker stops with the following fatal error message:
Stryker.NET could not compile the project after mutation. This is probably an error for Stryker.NET....
This message follows a warning:
Safe Mode! Stryker will remove all mutations in <someMethodName> and mark them as 'compile error.

Possible cause

The project code triggers an unknown bug in the 'safe mode' logic. Other possible but less likely causes:

• mutation injected without being tagged as such. Unlikely because mutation injection is done via a central method that ensures that tags are present.
• mutation logic corrupting code beyond repair. Possible, but would probably result in syntax related errors

Detailed explanation

Stryker injects all possible mutations in the source code and then removes the ones that trigger compilation error. The majority of these errors are directly linked to the mutated code, so Stryker can easily spot the problematic mutation and roll it back.
But some mutations result in control flow related errors, such as using an undefined variable. This type of errors are reported far from the mutation triggering it so Stryker cannot identify the offending one.

When this happens, Stryker relies on 'Safe mode'. Safe mode simply removes every mutation from the method, essentially restoring the method to its original state. This usually allows the compilation to proceed successfully. Not in your case.

Hypothesis

It is safe to assume that 'safe mode' failed to remove the offending mutation. It is possible that safe failed to properly identify the enclosing member, resulting in the removal of unrelated mutations.
It could be related to an error appearing in a local function that was triggered by a mutation in the enclosing method, or some other nested construct.

Next steps

Could you please share the code of the DeeAction method ? That may help us understand the issue and provide a workaround.

Why it did not happen in some older version

The rollback logic has not been revised for a long time. It is fair to assume the problem is related to some new mutation logic that is able to generate new mutations that trigger this problem.

Fix

It is impossible to provide a fix without having a better understanding of the cause or a reproduction project. But we could definitely improve on the error message so that it provides more context to pinpoint the cause.

[wasdfra]

Hello,

Thank you for the detailed feedback. In an effort to share the code without sharing too much, managed to find what code is causing the issue:

string sourceAPI = GetSourceAPIFromActionGroup("actionGroup.Name");

string GetSourceAPIFromActionGroup(string actionGroupName)
{
    string sourceAPI = actionGroupName.Split('.')
                                      .Reverse()
                                      .Skip(1)
                                      .FirstOrDefault();
    return sourceAPI;
}

This is part of the body of the DeeActionCode, and reducing the body just to this also replicates the issue. (Function call is different, but replicated like this during testing)

To note also that, during testing, if I removed the "using System.Linq;" it also failed to compile with exactly the same error.
I know that there are mutators specific for Linq, don't know if there are any that could have caused this?
If there are I may try to ignore those mutators on the stryker-config.json to prevent the crash in the meantime

[dupdob]

hummm
this may be a problem linked to local function. Can you try turning GetSourceAPIFromActionGroup as a method (instead of a local function)? this mays solve the issue.
You can also try adding a Stryker comment to disable mutation for this line.
Like adding // Stryker disable once Linq before the local function definition (it should disable Linq mutations for the whole function body)

[wasdfra]

Although moving it would not be possible due to other system limitations, moved to test and it still causes the issue.

Was checking the code on SharpLab to see if there was anything on the AST, you can check it here

[dupdob]

Thanks for this. I will unit test this when time permits, but I would be surprised if it triggers an issue. The problem lay be elsewhere in the code.
Note that the Stryker comment approach will solve the issue, assuming you can pinpoint the offending mutation(s).

[wasdfra]

So... Things just got weirder? I created an empty project, just with the file I sent and a UnitTest that executes it, and because I did so manually, instead of copy paste, I may have found that the cause is actually another? The 1st line, using System;

It is an unused reference on the example, but needed on the full code, and when I removed it from the example Stryker worked as expected, but not when it is present...

Any idea of a mutation that touches that?

[dupdob]

Thanks for this info, this may turn out to be useful, as weird as it looks.
I think that removing using System result in a different compilation error. Which is probably unambiguously linked to the mutation. In this case, Stryker is able to remove it without relying on safe mode.

In short, it confirms this is a Safe mode related bug, and that Stryker comment should help you to work around the issue.

[dupdob]

Update: I hope the provided workaround helped you. I just wanted to inform you that I am able to reproduce this bug, alas on the CI machine not locally. But this puts me in a better position to understand what is happening.

I am thinking this may be related to some faulty roll back logic. This may come to a surprise to many, but it is more complex to remove a mutation than to inject one in the first place.

[wasdfra]

Hello!

Thank you, and glad you were able to replicate! And sorry, was unable to test until now, but seems that comment did not work... Set the function like this:

        string GetSourceAPIFromActionGroup(string actionGroupName)
        {    
            // Stryker disable once Linq
            string sourceAPI = actionGroupName.Split('.')
                .Reverse()
                .Skip(1)
                .FirstOrDefault();
            return sourceAPI;
        }

And still got the error...

But found out something else, on the project that I created just for this, if I target net10.0 it does not fail, but if I target either net9.0 or net8.0 (the one the project should target) it fails... For reference my specific versions are:

• 8.0.419
• 9.0.115
• 10.0.104