Transform fails when project is targetting multiple frameworks

[CraigRichards]

Hi,
I regularly target multiple frameworks in the work I do and this constantly fails due to file-locking issues. I love this product and hope you can patch this easily.

Reproduction is simple.
I target multiple frameworks as the API client should work for all framework versions and my tests required different configurations depending on the environment. net4;net45;net451;net452;net461;net462;net47;net471;net472;net48;netcoreapp3.0;netcoreapp3.1;net5;net6;net7

Error Message

Severity Code Description Project File Line Suppression State
Error MSB4018 The "SlowCheetah.TransformTask" task failed unexpectedly.
System.IO.IOException: The process cannot access the file 'd:\Api.Client.Tests\appSettings.Dev3.json' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
at Microsoft.VisualStudio.Jdt.JsonTransformation..ctor(String transformFile, IJsonTransformationLogger logger)
at Microsoft.VisualStudio.SlowCheetah.JsonTransformer.Transform(String sourcePath, String transformPath, String destinationPath)
at Microsoft.VisualStudio.SlowCheetah.TransformTask.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__26.MoveNext() Api.Client.Tests D:\licensing-api\packages-cache\microsoft.visualstudio.slowcheetah\4.0.50\build\Microsoft.VisualStudio.SlowCheetah.targets 115

[KalleOlaviNiemitalo]

That's caused by a bug in another repository microsoft/json-document-transforms#21

https://github.com/microsoft/json-document-transforms/blob/36334de591fb5db86dcbd50500b3517ac4610422/src/Microsoft.VisualStudio.Jdt/JsonTransformation.cs#L44

It calls File.Open(transformFile, FileMode.Open, FileAccess.Read), which uses FileShare.None by default, thus does not allow anything else to read the same file at the same time. Should preferably just call File.OpenRead(transformFile), or alternatively specify FileShare.Read explicitly.

[mwpowellhtx]

I'm running into a similar issue, my targets are not running properly, like none whatsoever, seems like, under multi-targeting scenarios. Turns out, may be an issue with how NuGet is now treating build/ and buildMultiTargeting/, .props and .targets consumption. It is something probably, more than likely, new, since the time of during which these packages had last published. That's my two cents for what it's worth. I am working to resolve just that matter right now, in my packages.