Create workloads enumerator lazily in dotnet-new host

[JanKrivanek]

Problem

dotnet new is creating WorkloadInfoHelper that transitively causes creation of 'Microsoft.NET.Workload_.log' log in %temp% folder on each execution (regardles whether workloads constraints are being used or not).
This leads to unnecessary I/O operations. Also under specific circumstances dotnet new can fail due to log already being created (As log names are being created only with per-second granularity: https://github.com/dotnet/sdk/blob/main/src/Cli/dotnet/commands/dotnet-workload/install/NetSdkMsiInstallerClient.cs#L949) :

Unhandled exception: System.IO.IOException: The process cannot access the file 'C:\Users\jankrivanek\AppData\Local\Temp\Microsoft.NET.Workload_20221020_134925.log' because it is being used by another process.
  at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
  at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
  at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
  at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
  at System.IO.StreamWriter.ValidateArgsAndOpenPath(String path, Boolean append, Encoding encoding, Int32 bufferSize)
  at System.IO.File.CreateText(String path)
  at Microsoft.DotNet.Installer.Windows.TimestampedFileLogger..ctor(String path, Int32 flushThreshold, String[] logPipeNames)
  at Microsoft.DotNet.Workloads.Workload.Install.NetSdkMsiInstallerClient.Create(Boolean verifySignatures, SdkFeatureBand sdkFeatureBand, IWorkloadResolver workloadResolver, INuGetPackageDownloader nugetPackageDownloader, VerbosityOptions verbosity, PackageSourceLocation packageSourceLocation, IReporter reporter, String tempDirPath, RestoreActionConfig restoreActionConfig)
  at Microsoft.DotNet.Workloads.Workload.Install.WorkloadInstallerFactory.GetWorkloadInstaller(IReporter reporter, SdkFeatureBand sdkFeatureBand, IWorkloadResolver workloadResolver, VerbosityOptions verbosity, String userProfileDir, Boolean verifySignatures, INuGetPackageDownloader nugetPackageDownloader, String dotnetDir, String tempDirPath, PackageSourceLocation packageSourceLocation, RestoreActionConfig restoreActionConfig, Boolean elevationRequired)
  at Microsoft.DotNet.Workloads.Workload.List.WorkloadInfoHelper..ctor(VerbosityOptions verbosity, String targetSdkVersion, Nullable`1 verifySignatures, IReporter reporter, IWorkloadInstallationRecordRepository workloadRecordRepo, String currentSdkVersion, String dotnetDir, String userProfileDir, IWorkloadResolver workloadResolver)
  at Microsoft.DotNet.Cli.NewCommandParser.CreateHost(Boolean disableSdkTemplates, Boolean disableProjectContext, FileInfo projectPath, FileInfo outputPath, LogLevel logLevel)
  at Microsoft.DotNet.Cli.NewCommandParser.<GetCommand>g__GetEngineHost|11_0(ParseResult parseResult)
  at Microsoft.TemplateEngine.Cli.Commands.BaseCommand.CreateEnvironmentSettings(GlobalArgs args, ParseResult parseResult)
  at Microsoft.TemplateEngine.Cli.Commands.BaseCommand`1.InvokeAsync(InvocationContext context)
  at Microsoft.TemplateEngine.Cli.Commands.BaseCommand`1.Invoke(InvocationContext context)
  at System.CommandLine.Invocation.InvocationPipeline.<>c__DisplayClass4_0.<<BuildInvocationChain>b__0>d.MoveNext()

Sample repro

> start /b dotnet new --help & start /b dotnet new --help

System.IO.IOException: The process cannot access the file (...)

Solution

Create the workload provider lazily

Additional details

WorkloadInfoHelper is as well used in dotnet workload commands - so those have the same issue - e.g.:

> start /b dotnet workload list & start /b dotnet workload list

Unhandled exception: System.IO.IOException: The process cannot access the file (...)

however those command or probably much less likely to be executed in parallel or quick sequence

[JanKrivanek]

Should we as well right away make sure that logs do not colide (e.g. by adding PID)? https://github.com/dotnet/sdk/blob/main/src/Cli/dotnet/commands/dotnet-workload/install/NetSdkMsiInstallerClient.cs#L949

[vlada-shubina]

Should we consider just lazy implementation of IWorkloadsRepositoryEnumerator instead?
just a though

[vlada-shubina]

The fix looks good from dotnet new standpoint. On the workload side, better logging should be considered (do not fail on logging error, better naming, etc).