Generator Crashes Attempting to Load Plugin When Case Sensitivity is Enabled

[jorgerangel-msft]

Repro - run this command from an elevated terminal mkdir zzCaseSensitive && fsutil file setCaseSensitiveInfo zzCaseSensitive enable && cd zzCaseSensitive && git clone https://github.com/joseharriaga/openai-in-typespec && cd openai-in-typespec && npm install && pwsh .scripts\Invoke-CodeGen.ps1.

This results in an exception when attempting to load the plugin:

...
  Restored D:\s\zzCaseSensitive\openai-in-typespec\.plugin\generator\src\OpenAI.Library.Plugin.csproj (in 445 ms).
  OpenAI.Library.Plugin -> D:\s\zzCaseSensitive\openai-in-typespec\.plugin\generator\src\bin\Debug\net8.0\OpenAI.Librar
  y.Plugin.dll
...
Could not find a part of the path 'D:\S\ZZCASESENSITIVE\OPENAI-IN-TYPESPEC\.PLUGIN\DIST\GENERATOR'.
   at System.IO.Enumeration.FileSystemEnumerator`1.CreateDirectoryHandle(String path, Boolean ignoreNotFound)
   at System.IO.Enumeration.FileSystemEnumerator`1.Init()
   at System.IO.Enumeration.FileSystemEnumerable`1..ctor(String directory, FindTransform transform, EnumerationOptions options, Boolean isNormalized)
   at System.IO.Enumeration.FileSystemEnumerableFactory.UserFiles(String directory, String expression, EnumerationOptions options)
   at System.IO.Directory.InternalEnumeratePaths(String path, String searchPattern, SearchTarget searchTarget, EnumerationOptions options)
   at System.IO.Directory.GetFiles(String path, String searchPattern, EnumerationOptions enumerationOptions)
   at System.ComponentModel.Composition.Hosting.DirectoryCatalog.GetFiles()
   at System.ComponentModel.Composition.Hosting.DirectoryCatalog.Initialize(String path, String searchPattern)
   at System.ComponentModel.Composition.Hosting.DirectoryCatalog..ctor(String path, String searchPattern)
   at System.ComponentModel.Composition.Hosting.DirectoryCatalog..ctor(String path)
   at Microsoft.Generator.CSharp.PluginHandler.LoadPlugin(CommandLineOptions options)
   at Microsoft.Generator.CSharp.GeneratorRunner.RunAsync(CommandLineOptions options)
   at Microsoft.Generator.CSharp.Program.Run(CommandLineOptions options, GeneratorRunner runner)
Emitter "@open-ai/plugin" crashed! This is a bug.
Please file an issue at https://github.com/joseharriaga/openai-in-typespec/issues
...

[JoshLove-msft]

This seems to be due to MEF in DirectoryCatalog.cs:

Note that for non-Windows, we don't do the ToUpperInvariant, hence why the generator works fine on Linux/MacOS. So this is only an issue on Windows when enabling case-sensitive directories.