After upgrading Ktor to 2.0.0, I see this error in...

# ktor

[Robert Jaros]

After upgrading Ktor to 2.0.0, I see this error in IntelliJ only (no error when building from gradle):

Cannot access class 'kotlinx.serialization.json.Json'. Check your module classpath for missing or conflicting dependencies

when I try to use content negotiation:

install(ContentNegotiation) {
        json(json)
    }

I checked the dependencies but I can't see any obvious conflicts.

[Robert Jaros]

I see also this error:

Cannot access class 'kotlinx.coroutines.channels.ReceiveChannel'. Check your module classpath for missing or conflicting dependencies

in the same module when using websockets and channels.

[simon.vergauwen]

Did you include io.ktor:ktor-serialization-kotlinx-json as a dependency?

[Robert Jaros]

Yes

[Robert Jaros]

The project is building from gradle and is working fine with new Ktor. The errors are only in IntelliJ.

[simon.vergauwen]

Oh, in that case you might want to try refreshing Gradle inside IntelliJ cmd+shift+a -> Refresh Gradle Dependencies.

That triggers IntelliJ to rescan and index the dependencies again, so it might correctly resolve the code after that.

[Robert Jaros]

Unfortunately it didn't help

[simon.vergauwen]

Strange, this is working for me on Ktor 2.0 with KotlinX Serialization for server.

[simon.vergauwen]

https://github.com/nomisRev/ktor-arrow-example/blob/main/build.gradle.kts

[simon.vergauwen]

Here is the configuration of Ktor: https://github.com/nomisRev/ktor-arrow-example/blob/main/src/main/kotlin/io/github/nomisrev/config/ktor.kt

[simon.vergauwen]

I have an api dependency on KotlinX Coroutines through Arrow Fx Coroutines though, and KotlinX Serialization Gradle Plugin adds a dependency to KotlinX Seriliaziation Core.

[Robert Jaros]

I see a lot more other errors in IntelliJ as I check different files in my project. All of them are about serialization/coroutines incompatibility or accessibility and not all are Ktor specific. So I think I have some other general problem with my project and IntelliJ. I'll make some more tests with previous Kotlin and Ktor versions.

[Aleksei Tirman [JB]]

Please try to invalidate caches in IDE.

[Robert Jaros]

Tried that already, doesn't help

[Aleksei Tirman [JB]]

Then I can only suggest removing a Gradle cache by deleting ~/.gradle and ~/.m2 folders.

[Robert Jaros]

It doesn't seem like a cache problem. I have found a different project with similar error:

[Robert Jaros]

I can fix this error by changing one dependency in common module from api type to implementation type

[Robert Jaros]

When I go back to api the error is back as well.

[Robert Jaros]

It's a Ktor project with implementation("io.ktor:ktor-server-core:$ktorVersion") dependecy in jvmMain source set, so coroutines version 1.6.0 is on the classpath.

[Robert Jaros]

It works fine from gradle as well, just this error in IntelliJ.

[Robert Jaros]

adding api("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.0") in common source set dosn't fix the problem
but implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.0") does fix the problem

[Robert Jaros]

It's a bit crazy 😉

[Aleksei Tirman [JB]]

This is most likely it.

[Robert Jaros]

Thanks. It does look similar.