GraphQLError in Kotlin is cause an Accidental Override

[vagostep]

When i try to create a custom exception that implements GraphQLError cause an Accidental Override in the getMessage error in Kotlin

It's cause because the interface GraphQLError have a method called getMessage(), and the class Throwable also have the same method.

So, the custom exceptions need extends of Throwable and implements GraphQLError and this cause a compiler error "Accidental Override"

[bbakerman]

Can you explain more about accidental override rules in Kotlin? I am not familiar with the language restorations and how we are not playing ball correctly

…

On Sat., 21 Apr. 2018, 17:50 Andres Diaz, ***@***.***> wrote: When i try to create a custom exception that implements GraphQLError cause an Accidental Override in the getMessage error in Kotlin — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1022>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABlbSWKJcHLZa_GCoCIR31jQyuqWmpxMks5tq6msgaJpZM4TeoYM> .

[vagostep]

@bbakerman In Kotlin, the class Throwable has a member called "message". Kotlin automaticaly create a setter and getter with this name (getMessage and setMessage). So, this method cause the accidental override with the abstract method in the interface GraphQLError getMessage() when i extends of Throwable and implements GraphQLError.

Here was the same problem notify by another user: https://stackoverflow.com/questions/48698699/accidental-override-the-following-declarations-have-the-same-jvm-signature-wh

[bbakerman]

I am not sure how we can solve this. The graphql spec says that graphql errors MUST have a "message" attribute. Hence GraphqlError having a getMessage method and hence JSON conversion just working.

Its very convinenting to have exceptions implement GraphqlError to they dont have to be translated manually.

I am not sure how to work around this for Kotlin??

[bbakerman]

I have asked colleagues at Atlassian about this problem.

The consensus was that this is a challenge even in native Kotlin

interface GraphQLError {
	fun getMessage(): String
}

class FeatureFlagFetchException(s: String?) : RuntimeException(s), GraphQLError

Their suggestion as a work around was to declare a .java file that represents the custom exception

[vagostep]

@bbakerman Great. It would not have even occurred to me to use Java-Kotlin interoperability in this case. I will implement it

[Arcnor]

For anybody else stumbling upon this problem, the related Kotlin issue is https://youtrack.jetbrains.com/issue/KT-6653 (I also opened a ticket with the GraphQL specific problem that got closed as duplicated of the first https://youtrack.jetbrains.com/issue/KT-24822)

[ryandanielspmc]

Based on the links that @Arcnor provided, there is a solution there that worked for me. Below is my implementation of that solution.

class CustomException(@JvmField override val message: String) : RuntimeException(message), GraphQLError  {

    override fun getMessage(): String? = super.message

    override fun getLocations(): MutableList<SourceLocation> = mutableListOf()

    override fun getErrorType(): ErrorClassification = CustomErrorClassification()
}

class CustomErrorClassification : ErrorClassification

[darko1002001]

I can confirm this doesn't cause an issue now, but it will cause a problem when you declare it as open or abstract and try to extend this class. How do you extend this custom exception now?

[binkoni]

Based on the links that @Arcnor provided, there is a solution there that worked for me. Below is my implementation of that solution.

class CustomException(@JvmField override val message: String) : RuntimeException(message), GraphQLError  {

    override fun getMessage(): String? = super.message

    override fun getLocations(): MutableList<SourceLocation> = mutableListOf()

    override fun getErrorType(): ErrorClassification = CustomErrorClassification()
}

class CustomErrorClassification : ErrorClassification

This solution is not working anymore in Kotlin 1.6

@JvmField cannot be applied to a property that overrides some other property

[bonobonohu]

class CustomException(@JvmField override val message: String) : RuntimeException(message), GraphQLError {

now i get: "JvmField cannot be applied to a property that overrides some other property". 😞

[bbakerman]

See #1022 (comment)

[bonobonohu]

See #1022 (comment)

"Their suggestion as a work around was to declare a .java file that represents the custom exception"

• haha, i came to this same conclusion as well only a few minutes ago. 😉
  only... only in this case you won't have a "pure" Kotlin application - whatever the meaning of this. 🤷‍♂️

[bbakerman]

only in this case you won't have a "pure" Kotlin application
Think of it as a pure JVM application however ;)

[bonobonohu]

hey guys, i've just ran into this page accidently now:
https://kotlinlang.org/docs/java-to-kotlin-interop.html#handling-signature-clashes-with-jvmname
i'm not sure, since i did not cope with this since then, but... could we utilize this to get rid of this issue?
@get:JvmName("message") maybe?
will get into context/try it out soon and keep you updated (or delete this comment, if it turns out i'm on the wrong track).

[ArisPoz]

So the only workaround to this issue is to create a Java class with the custom exception?
Alright alright, lets go with the pure JVM way then 👍

[chuck-park]

make custom exception class extends the java module extends RuntimeException and implement GraphQLError.
It said "because a Kotlin class can’t extend RuntimeException and implement GraphQLError at the same time."

[Satook]

There is a useable class already in GraphQL-Java. GraphqlErrorException

Was added to address this ticket: #1743

The file is here: https://github.com/graphql-java/graphql-java/blob/18.x/src/main/java/graphql/GraphqlErrorException.java
It was added in v14 and is still there now for Kotlin compat.