Kotlin language server anyone get it working?

[AddictArts]

I've managed to get the java support working, however Kotlin server exits. The process is opaque and hard to know what the issue is. Anyone got it working? Thanks in advance.

I'm trying to use the language server at: https://github.com/fwcd/kotlin-language-server which the wiki references with no instructions.

[AddictArts]

After some research VIM uses a thing that runs the vscode ext coc.vim. This is likely something we don't have in the helix world.

Is there any alternative I wonder?

[kirawi]

What does :log-open say after running hx -v and opening a Kotlin file?

[masonlouchart]

Thank you! It was helpful. I could acknowledge my Java version was not compatible, and updating fixed my issue.

[AddictArts]

Thanks @kirawi

This is what I see, unsure of why slf4j failed to load since it is in the classpath. I don't find the support crucial and can live without it for now. Maybe this info will help someone else. I am not a heavy Kotlin user and don't plan on it.

2023-09-06T14:49:10.984 helix_lsp::transport [ERROR] err <- "SLF4J: Failed to load class \"org.slf4j.impl.StaticLoggerBinder\".\n"
2023-09-06T14:49:10.985 helix_lsp::transport [ERROR] err <- "SLF4J: Defaulting to no-operation (NOP) logger implementation\n"
2023-09-06T14:49:10.985 helix_lsp::transport [ERROR] err <- "SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.\n"
2023-09-06T14:49:11.715 helix_lsp::transport [ERROR] err <- "Sep 06, 2023 2:49:11 PM org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint lambda$recursiveFindRpcMethods$2\n"
2023-09-06T14:49:11.715 helix_lsp::transport [ERROR] err <- "SEVERE: A delegate object is null, jsonrpc methods of 'public default org.eclipse.lsp4j.services.NotebookDocumentService org.eclipse.lsp4j.services.LanguageServer.getNotebookDocumentService()' are ignored\n"
2023-09-06T14:49:30.125 helix_lsp [ERROR] failed to initialize language server: request 0 timed out
2023-09-06T14:50:01.086 helix_lsp::transport [ERROR] Tried sending response into a closed channel (id=Num(0)), original request likely timed out

[mantono]

I got the same issue :/

2023-11-24T16:09:30.988 helix_lsp::transport [ERROR] kotlin-language-server err <- "SLF4J: Failed to load class \"org.slf4j.impl.StaticLoggerBinder\".\n"
2023-11-24T16:09:30.989 helix_lsp::transport [ERROR] kotlin-language-server err <- "SLF4J: Defaulting to no-operation (NOP) logger implementation\n"
2023-11-24T16:09:30.989 helix_lsp::transport [ERROR] kotlin-language-server err <- "SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.\n"
2023-11-24T16:09:31.864 helix_lsp::transport [ERROR] kotlin-language-server err <- "nov. 24, 2023 4:09:31 EM org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint lambda$recursiveFindRpcMethods$2\n"
2023-11-24T16:09:31.864 helix_lsp::transport [ERROR] kotlin-language-server err <- "SEVERE: A delegate object is null, jsonrpc methods of 'public default org.eclipse.lsp4j.services.NotebookDocumentService org.eclipse.lsp4j.services.LanguageServer.getNotebookDocumentService()' are ignored\n"

I don't think the absence of a logging implementation is the issue, but maybe the last line is relevant.

EDIT: The language server DO actually work for me, it is just that it requires some time to start up before it is working, so I guess my "errors" above was not actually indicating any real issue.

[mantono]

Okay, sometimes it works for me, and sometimes I get the exact same error as you and it doesn't work...

2023-11-27T08:35:24.316 helix_lsp [ERROR] failed to initialize language server: request 0 timed out
2023-11-27T08:35:36.990 helix_lsp::transport [ERROR] Tried sending response into a closed channel (id=Num(0)), original request likely timed out

The interesting thing is that I got one terminal where I have helix open with a Kotlin project and everything works fine, and in the second terminal I get this issue. I don't know if it fails to initialize the server sometimes, or it is an issue with trying to initialize it when there is already an instance of the language server running 🤔

[covelloz]

+1 tried experimenting with Kotlin in Helix the LSP fails to start. I'm getting [ERROR] failed to initialize language server: request 0 timed out every time. My project is quite large - for it to work in neovim I had to set an ENV variable JAVA_OPTS and increase the memory allocation to be very large†. Unusable in Helix though current state.

† ref troubleshooting: https://github.com/fwcd/kotlin-language-server/blob/main/TROUBLESHOOTING.md

[koalazub]

Think it's worth reviving this thread on account of JB really putting in the work to get an actual kotlin-lsp working. See here:
https://github.com/Kotlin/kotlin-lsp

There's a slew of commits being made to quickly get things up and running. I can see that the LSP is pretty large(like 600MB large) but they're pushing through really rapidly

[goldenratio]

I tried with Jetbrain's kotlin-lsp, https://github.com/Kotlin/kotlin-lsp
Doesn't seem to work. Maybe I am missing something.

# kotlin
[language-server.kotlin]
command = "kotlin-lsp"

[[language]]
name = "kotlin"
language-servers = [ "kotlin" ]

I am getting,
No configured language server supports hover

helix log:

2025-07-14T13:15:38.463 helix_lsp::transport [ERROR] kotlin err <- "WARNING: package sun.awt.windows not in java.desktop\n"
2025-07-14T13:15:38.463 helix_lsp::transport [ERROR] kotlin err <- "WARNING: package sun.awt.X11 not in java.desktop\n"
2025-07-14T13:15:38.463 helix_lsp::transport [ERROR] kotlin err <- "WARNING: package com.sun.java.swing.plaf.gtk not in java.desktop\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "Exception in thread \"main\" java.net.BindException: Address already in use\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/sun.nio.ch.Net.bind0(Native Method)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/sun.nio.ch.Net.bind(Net.java:511)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/sun.nio.ch.Net.bind(Net.java:500)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/sun.nio.ch.NioSocketImpl.bind(NioSocketImpl.java:630)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/java.net.ServerSocket.bind(ServerSocket.java:326)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/java.net.ServerSocket.<init>(ServerSocket.java:222)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat java.base/java.net.ServerSocket.<init>(ServerSocket.java:138)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.lsp.implementation.TcpServerKt.tcpServer(tcpServer.kt:20)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.KotlinLspServerKt.tcpConnection(KotlinLspServer.kt:161)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.KotlinLspServerKt.access$tcpConnection(KotlinLspServer.kt:1)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.RunKotlinLspCommand$run$1$1.invokeSuspend(KotlinLspServer.kt:62)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.RunKotlinLspCommand$run$1$1.invoke(KotlinLspServer.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.RunKotlinLspCommand$run$1$1.invoke(KotlinLspServer.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.snapshot.api.impl.core.LSServerAnalyzerImplKt$createServerStarterAnalyzerImpl$1$start$2.invokeSuspend(LSServerAnalyzerImpl.kt:144)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.snapshot.api.impl.core.LSServerAnalyzerImplKt$createServerStarterAnalyzerImpl$1$start$2.invoke(LSServerAnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.snapshot.api.impl.core.LSServerAnalyzerImplKt$createServerStarterAnalyzerImpl$1$start$2.invoke(LSServerAnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2$2.invokeSuspend(AnalyzerImpl.kt:319)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:44)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.CoroutineScopeKt.coroutineScope(CoroutineScope.kt:285)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2.invokeSuspend(AnalyzerImpl.kt:318)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:44)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:166)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.BuildersKt.withContext(Unknown Source)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2.invokeSuspend(AnalyzerImpl.kt:243)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt$withAnalyzerImpl$2.invoke(AnalyzerImpl.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat fleet.util.async.JobExtKt$withCoroutineScope$2.invokeSuspend(JobExt.kt:47)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat fleet.util.async.JobExtKt$withCoroutineScope$2.invoke(JobExt.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat fleet.util.async.JobExtKt$withCoroutineScope$2.invoke(JobExt.kt)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:44)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.CoroutineScopeKt.coroutineScope(CoroutineScope.kt:285)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat fleet.util.async.JobExtKt.withCoroutineScope(JobExt.kt:47)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat fleet.util.async.JobExtKt.withCoroutineScope$default(JobExt.kt:40)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.bootstrap.AnalyzerImplKt.withAnalyzerImpl(AnalyzerImpl.kt:170)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.analyzer.api.AnalyzerKt.withAnalyzer(Analyzer.kt:66)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.snapshot.api.impl.core.LSServerAnalyzerImplKt$createServerStarterAnalyzerImpl$1.start(LSServerAnalyzerImpl.kt:89)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat com.jetbrains.ls.kotlinLsp.RunKotlinLspCommand$run$1.invokeSuspend(KotlinLspServer.kt:55)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:613)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:1189)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:778)\n"
2025-07-14T13:15:39.460 helix_lsp::transport [ERROR] kotlin err <- "\tat kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:765)\n"
2025-07-14T13:15:39.852 helix_lsp [ERROR] failed to initialize language server: server closed the stream
2025-07-14T13:15:39.852 helix_lsp::transport [ERROR] kotlin err: <- StreamClosed

[vitorfloriano]

The official kotlin-lsp is in an experimental, pre-alpha, exploratory phase with the intention to be productionized.

[AhmadNaruto]

[language-server.kotlin]
command = "kotlin-lsp"
args = [ "--stdio" ] 

[[language]]
name = "kotlin"
language-servers = [ "kotlin" ]