jextract: Organize java known functional interfaces

[AmrDeveloper]

Organize the Java known functional interfaces information in one place

Issue #811

[ktoso]

I'd like this to be if let known = KnownJavaFunctionalInterface(method, nativeResult.javaType) { ... } else { "apply" } maybe, so centralize the matching the signatures to the types

[AmrDeveloper]

I updated it to depend on parameters and result types, not sure if there is a better syntax or a way to do this

[ktoso]

Digging through this a bit more, the shape we want is more like:

struct KnownJavaFunctionalInterface: Sendable {
  let javaType: JavaType
  let method: String
  let parameters: [JavaType]
  let result: JavaType

  static let runnable = KnownJavaFunctionalInterface(
    JavaType.javaLangRunnable,
    method: "run",
    parameters: [],
    result: .void
  )

because I want the type name, method name, and types all in one place, rather than spread out in the other funcs.

Hope you don't mind if I apply this small change and we merge this; looking forward to follow ups handling the other types!

[ktoso]

I also noticed the functional interface usage isn't really complete... We're still emitting the @FunctionalInterface public interface Function even though we don't use it anymore. we Should fix that as well.

[AmrDeveloper]

Digging through this a bit more, the shape we want is more like:

struct KnownJavaFunctionalInterface: Sendable {
  let javaType: JavaType
  let method: String
  let parameters: [JavaType]
  let result: JavaType

  static let runnable = KnownJavaFunctionalInterface(
    JavaType.javaLangRunnable,
    method: "run",
    parameters: [],
    result: .void
  )

because I want the type name, method name, and types all in one place, rather than spread out in the other funcs.

Hope you don't mind if I apply this small change and we merge this; looking forward to follow ups handling the other types!

I don't mind, and I can do that too :D

[AmrDeveloper]

I also noticed the functional interface usage isn't really complete... We're still emitting the @FunctionalInterface public interface Function even though we don't use it anymore. we Should fix that as well.

Yes, I mentioned that here

#820 (comment)

Will handle it in follow-up

[ktoso]

Would you want to do the follow up please?

Inside

  /// Print FFM Java binding descriptors for the imported Swift API.
  package func printJavaBindingDescriptorClass(
    _ printer: inout JavaPrinter,
    _ decl: ExtractedFunc,
  ) {

before we do

printJavaBindingDescriptorClass(&printer, cFunc, symbolLookup: currentSymbolLookup) { printer in

we need to guard it like

if let known = KnownJavaFunctionalInterface.find(parameters: cParameterTypes, result: cResultType) {
  // skip, this is a known type/shape (e.g. Runnable),
  // so there's no need to emit an one-off functional interface for it.
  continue
}

Would you make a follow up PR with that please?

[ktoso]

Thanks!

[AmrDeveloper]

Would you want to do the follow up please?

Inside

  /// Print FFM Java binding descriptors for the imported Swift API.
  package func printJavaBindingDescriptorClass(
    _ printer: inout JavaPrinter,
    _ decl: ExtractedFunc,
  ) {

before we do

printJavaBindingDescriptorClass(&printer, cFunc, symbolLookup: currentSymbolLookup) { printer in

we need to guard it like

if let known = KnownJavaFunctionalInterface.find(parameters: cParameterTypes, result: cResultType) {
  // skip, this is a known type/shape (e.g. Runnable),
  // so there's no need to emit an one-off functional interface for it.
  continue
}

Would you make a follow up PR with that please?

Yes, I will. I just wanted to make them small incremental changes so we can easily review and merge them in short iterations, and I can get a review of the language features to use :D

Thanks