The "ConvertMain" task failed unexpectedly

[interrubke]

I have around 15 convert tasks in my project, like below.

 <Target Name="ConvertHubMessages" BeforeTargets="PrepareForBuild">
    <Message Text="Generating model :  HubMessages" Importance="high" />
    <ConvertMain WorkingDirectory="SignalRHubs/HubMessages/" ConvertDirectory="clientApp/server-models/hubMessages/" />
  </Target>
  <Target Name="ConvertEnums" BeforeTargets="PrepareForBuild">
    <Message Text="Generating model :  Enums" Importance="high" />
    <ConvertMain WorkingDirectory="../../src/SomeProject.BackOffice.Common/Enums/" ConvertDirectory="clientApp/server-models/enums/" />
  </Target>
  <Target Name="ConvertAccount" BeforeTargets="PrepareForBuild">
    <Message Text="Generating model :  Account" Importance="high" />
    <ConvertMain WorkingDirectory="Controllers/Api/Account/Models/" ConvertDirectory="clientApp/server-models/account/" />
  </Target>

When i build from scratch (no models generated) it works ok, but the second and other times the ConvertMain task crashes with the error:

  Error	MSB4018	The "ConvertMain" task failed unexpectedly.
System.UnauthorizedAccessException: Access to the path 'C:\projects\SomeProject\BackOffice\src\SomeProject.BackOffice.Web\clientApp\server-models\hubMessages' is denied.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileSystemEnumerableIterator`1.CommonInit()
   at System.IO.FileSystemEnumerableIterator`1..ctor(String path, String originalUserPath, String searchPattern, SearchOption searchOption, SearchResultHandler`1 resultHandler, Boolean checkHost)
   at System.IO.Directory.GetDirectories(String path)
   at MTT.ConvertService.DeleteDirectory(String path, Int32 iteration)
   at MTT.ConvertService.GetConvertDirectory()
   at MTT.ConvertService.Execute()
   at MSBuildTasks.ConvertMain.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()	SomeProject.BackOffice.Web	C:\projects\SomeProject\BackOffice\src\Project.BackOffice.Web\SomeProject.BackOffice.Web.csproj	131	

It is not always the first one, more or less a random convert task. Is this related to the multiple tasks setup? Is there a way to prevent this?

[CodySchrank]

I've never tried to do multiple conversions like this. I've only ever done from one folder to another, so honestly I have no idea how MTT would handle this. I'll try making a test project to test this though and see if there is anything i can do.

[interrubke]

Thanks.
We are using multiple converts for api models, enums (from another project), and so one.. these go into one server-models folder for the frontend.

[CodySchrank]

MTT wasn't really designed to have multiple instances running, that is why you get access denied, another instance is already using those resources. I'm sure some kind of parallelization is possible, but I'm not really sure what that looks like with how it is setup now.

[nitro-codes]

@interrubke cascade the execution of the target tasks with either DependsOnTargets or AfterTargets like so...

  <Target Name="ConvertHubMessages" BeforeTargets="PrepareForBuild">
    ...
  </Target>
  <Target Name="ConvertEnums" BeforeTargets="PrepareForBuild" AfterTargets="ConvertHubMessages">
    ...
  </Target>
  <Target Name="ConvertAccount" BeforeTargets="PrepareForBuild" AfterTargets="ConvertEnums">
    ...
  </Target>

https://docs.microsoft.com/en-us/visualstudio/msbuild/target-build-order?view=vs-2019