If I put a _ViewStart.cshtml in the root of the ~/Areas folder, razorgenerator is not able to detect that it should choose MvcViews for that by default.

The code in GetRazorCodeTransformer() tries to guess the generator by convention, or read it from the cshtml file comments. It doesn't include conventions for _ViewStart files specifically so returns null and this causes razorgenerator to blow up.

The workaround now is to add the generator comment but RG should probably detect this and handle it gracefully. You'd probably have to crack open the MVC source to determine all of the searched locations for _ViewStart to identify other paths that should be auto-detected.

This was via the razorgenerator msbuild task.