Is it possible to modify AST like Lombok, instead of generating code?

# ksp

[zyfuni]

Is it possible to modify AST like Lombok, instead of generating code?

[jw]

You'll want to write a compiler plugin instead

[Edoardo Luppi]

@jw I did try and it's really time consuming. I guess we should wait for K2 and the real compiler plugin infrastructure described in one of the recent talks

[Javier]

do you want to modify the frontend part? or the backend?

Modifying the frontend is limited to a few things like adding super types or modifying the status

If it is the backend, the backend APIs are not changing a lot so you wouldn’t see a lot of differences between the current state and 2.0.0

[zyfuni]

@Javier I can't exactly point out whether what I want to do belongs to frontend or backend. However, I intend to finish my work on Transformation API.

[Javier]

do you need to modify anything that user needs to know when he is writing on the IDE?

For example, if the user create a class which is annotated and your plugin adds a supertype

@AddSuperTypeBar
class Foo

interface Bar

Fun main() {
   // doesn't compile even if you fix it
   // on the backend side, as it is marked as
   // error on the IDE (frontend)
   val bar: Bar = Foo() 
)

Or your user doesn't care about anything on the IDE?

fun foo(): Foo = TODO()

Fun main() {
   // it is valid on the IDE (frontend)
   // but it would crash if you don't replace
   // the body of `foo()` with valid code, so
   // in backend you can `fun foo(): Foo = Foo()`
   val foo: Foo = foo()
)

[zyfuni]

@Javier It's frontend.

[Javier]

and what do you need to modify? because it is very restrictive

[zyfuni]

Someone aksed same question, and sound like ksp don't have capability to do this.

[Javier]

and probably you will want to move this question to #compiler

[Javier]

no, ksp only codegen code

[Javier]

but, depending on what you want to do, maybe you can't even with a compiler plugin, so I would ask in #compiler

[zyfuni]

Almost the same as the example you provided, does it have a ready-made solution?

[zyfuni]

Yes, #compiler doesn't look like what I want.

[zyfuni]

Predictably, I also need to provide an Idea plugin like lombok.

[Javier]

Sorry but I don't know what lombok does, without more detailed info of what you want to do, I can't help more