Make AdditionalFiles available during source generator Initialize step

[macon]

I'm trying to augment the protobuf/C# codegen. I want to pass a set of AdditionalFiles (pointing at my .protos) to my source generator and scan these to set up some SyntaxReceivers. Unfortunately I need to set up the SyntaxReceiver in the Initialize method of the source generator and at this point the AdditionalFiles are not available to me. The AdditionalFiles is only available in the GeneratorExecutionContext parameter of the Execute method.

It seems right to have all the config information that the consuming project is giving to the generator (e.g. AdditionalFiles) available at the Initialize step.

[ufcpp]

This is just WIP? RegisterForAdditionalFileChanges already exists but internal.

roslyn/src/Compilers/Core/Portable/SourceGeneration/GeneratorContexts.cs

Line 120 in 230d0d0

internal void RegisterForAdditionalFileChanges(EditCallback<AdditionalFileEdit> callback)

[jasonmalinowski]

@macon Why do you want them in the initialize step? The model here is Initialize() you are just specifying how your generator works and it only runs once; all the actual work happens in Execute. But I can imagine you have some case where you could optimize your syntax walk if you had already processed the additional files first?

[ryzngard]

The natural follow up is: how does this change when files are added/removed between design time builds? Do we initialize all generators again?