I have an issue with kotlin `Result` and AOP ```p...

# spring

[thanksforallthefish]

I have an issue with kotlin Result and AOP

package com.example.demo

import org.aspectj.lang.ProceedingJoinPoint
import org.aspectj.lang.annotation.Around
import org.aspectj.lang.annotation.Aspect
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.stereotype.Component
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RequestParam
import org.springframework.web.bind.annotation.RestController

@SpringBootApplication
class DemoApplication

fun main(args: Array<String>) {
	runApplication<DemoApplication>(*args)
}

@RestController
@RequestMapping("/test")
class TestController(val repository: TestRepository) {
	@GetMapping
	fun test(@RequestParam(defaultValue = "#{{}}") list: List<Int>) =
		repository.getList(list)
				.getOrElse { list }
}

@Component
class TestRepository {
	fun getList(list: List<Int>): Result<List<Int>> = runCatching { throw RuntimeException("Error") }
}

@Aspect
@Component
open class MyOhMy {
	@Around("within(com.example.demo..*Repository+)")
	fun aspect(joinPoint: ProceedingJoinPoint): Any? =
			joinPoint.runCatching {
				proceed()
			}.getOrThrow()
}

issue is that getOrThrow in the aspect actually throws, while I would expect to return a Result<Failure

more in thread

[thanksforallthefish]

I would expect the above code to work like

val result = runCatching { throw RuntimeException("test") }
val wrap = runCatching { result }
println(wrap.getOrThrow())
println(result.getOrNull())

but I think something in ProceedingJoinPoint messes up with my expectation

[Dibya Ranjan]

Hey @thanksforallthefish -

Returns the encapsulated value if this instance represents success or throws the encapsulated exception if it is failure.
This function is shorthand for getOrElse { throw it } (see getOrElse).

there is nothing wrong with the PJP

[thanksforallthefish]

@Dibya Ranjan thanks for the answer. I forgot to actually write down new findings here, but I think it has to do with mangling: https://github.com/Kotlin/KEEP/blob/master/proposals/inline-classes.md#mangling

a similar case: https://youtrack.jetbrains.com/issue/KT-34437

what I meant was, that with

joinPoint.runCatching { proceed() }.getOrThrow()

my expectation was to a <Result<Result<…>>, where Result<…> is a Failure, but I think because of mangling (which fyi is not superclear to me), that gets unwrapped and I get Result<…> and then ofc getOrThrow throws

[thanksforallthefish]

you can try the small snippet

Marco Davi  [3:54 PM]
I would expect the above code to work like

val result = runCatching { throw RuntimeException("test") }
val wrap = runCatching { result }
println(wrap.getOrThrow())
println(result.getOrNull())

in this example wrap.getOrThrow does not throw the exception (as expected)

[Dibya Ranjan]

trying

[Dibya Ranjan]

Aren’t these two code equivalent?

val result = runCatching { throw RuntimeException("test") }
val wrap = runCatching { result }
println(wrap.getOrThrow())
println(result.getOrNull())

to

val x = runCatching {
        runCatching { throw RuntimeException("Failed") }
    }
    println(x.getOrThrow())
    println(x.getOrNull())

I don’t see .getOrThrow() called on val result = runCatching { throw RuntimeException("test") }. 🤔

[thanksforallthefish]

I have val result: Result<…> and val wrap: Result<Result<…>>, you have only val x: Result<Result<…>>

the only difference should be that println(result.getOrNull()) //prints null while println(x.getOrNull()) //prints something else

[thanksforallthefish]

the point is that runCatching { result } is equivalent to Result.success(result) , so calling getOrSomething should return result (and it does, until that code in used in PJP, then mangling(?) messes things up)