not sure how to replace or add to method contents

[BrannonKing]

Your example shows how to add an additional class. I want to augment my actors project (https://github.com/BrannonKing/Kts.Actors) so that I can perform the actor insertion based on an attribute. To do that, I have to add a class field, rename and privatize the method the code generation attribute was on, and make a new method to call, among other things. By returning a list of generated code, how can I modify existing code? Or what exactly is represented by the GenerateAsync method's return value?

[BrannonKing]

I guess what I'm asking for is the traditional AOP example: add logging to the start and end of a method (or every method in a class).

[weltkante]

Last time I looked at it you could only add code files with code generators, not replace them, so it is probably not possible with this tool. You may get it working by modifying the msbuild step to exclude the original file from the build and only use the generated file.

[masaeedu]

@BrannonKing GenerateAsync's result is a collection of syntax nodes that will get injected into a new hidden file in the project where the attribute is used. One kind of ugly approach is to have your users put a prefix on the class that you will then strip to produce a new class name. e.g. [YourAttribute] class _MyClass { ... }. Everything else in the code uses the new class name MyClass, which you are free to generate however you wish (e.g. by copying the declaration of the original class and replacing the implementation of certain methods).

[weltkante]

Instead of a name prefix a better idea would probably to put this "template" into a separate namespace - less ugly.

[masaeedu]

@weltkante How do you emit namespaces with this tool? From what I can of the GenerateAsync API, it seems to be limited to emitting MemberDeclarationSyntax nodes.

[masaeedu]

@weltkante In case you're interested, I found out how you can simulate namespaces with this tool: static classes can be imported in C# 6 with using static.

[amis92]

@BrannonKing To answer the original question:

what exactly is represented by the GenerateAsync method's return value?

Results from all run generators will be joined together and output into a new file added to the core compilation. So, you're limited by C# - you can create new partials of classes, or create entirely new types, but you simply cannot modify already written code.

Since this answers the original question, I'm closing the issue.

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As a followup on @weltkante and @masaeedu 's discussion

How do you emit namespaces with this tool?

You can now implement the IRichCodeGenerator interface (it's not yet documented aside from PR #80).
In it you can now return many additional types of Nodes.