GraphQLError in Kotlin is cause an Accidental Override

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"

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> .

@bbakerman

@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

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??

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

@bbakerman

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

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)

@Arcnor

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

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?

@Arcnor

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

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". 😞

See #1022 (comment)

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. 🤷‍♂️

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

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).

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 👍

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."

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.

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GraphQLError in Kotlin is cause an Accidental Override #1022

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bbakerman commented on Apr 23, 2018

andres29diaz commented on Apr 23, 2018

bbakerman commented on May 6, 2018

bbakerman commented on May 6, 2018

andres29diaz commented on May 7, 2018

Arcnor commented on Jun 10, 2018

ryandanielspmc commented on Nov 7, 2020

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