Cannot find `csc.exe` when running in Unity

[DemaCya]

Unity reports an error when using ProcessTemplateAsync: TemplatingEngineException: Could not find csc in host Mono installation.I tried 2019.4.22 and 2022.3.24, and also tried Mono's .Net Standard 2.0/2.1, .Net Framework, and .Net 4.8, but I still get this error. I imported it using NuGetForUnity and used it directly.What am I doing wrong? I'm really upset.

[mhutch]

When running in the Mono runtime, it looks for csc.exe in the same directory as the executing assembly that contains System.Object: https://github.com/mono/t4/blob/main/Mono.TextTemplating/Mono.TextTemplating.CodeCompilation/RuntimeInfo.cs#L106

Presumably Unity's bundled version of Mono is modified and differs from the standard layout. If you can provide alternate logic, I'd be happy to integrate it.

[indie-hub]

Hello!
Because I faced the same issue, here's a "possible" solution.

var runtimeDir = Path.GetDirectoryName (typeof (object).Assembly.Location);
var csc = Path.Combine (runtimeDir, "csc.exe");
if (!File.Exists (csc)) {
  var parentRuntimeDir = Path.Combine (runtimeDir, "..");
  string[] cscs = Directory.GetFiles (parentRuntimeDir, "csc.exe", SearchOption.AllDirectories);
  
  if (!cscs.Any()) {
	  return FromError (RuntimeKind.Mono, "Could not find csc in host Mono installation");
  }
  
  csc = cscs[0];
}