LSP crash on opening some files

[gertvv]

I've tried to set up jls in Helix on Linux. It seems to work on simple source files but crashes on others. It doesn't look to me to be Helix-specific but can't work out what it could be. Log:

2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "08:26:46.217\tSEVERE\tMain main\tjava.lang.reflect.InvocationTargetException\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "java.lang.AssertionError: java.lang.reflect.InvocationTargetException\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.source.util.Trees.getJavacTrees(Trees.java:94)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.source.util.Trees.instance(Trees.java:71)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.CompileBatch.<init>(CompileBatch.java:46)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaCompilerService.doCompile(JavaCompilerService.java:95)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaCompilerService.loadCompile(JavaCompilerService.java:86)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaCompilerService.compileBatch(JavaCompilerService.java:123)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaCompilerService.compile(JavaCompilerService.java:440)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaCompilerService.compile(JavaCompilerService.java:424)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.hover.HoverProvider.hover(HoverProvider.java:33)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.JavaLanguageServer.hover(JavaLanguageServer.java:565)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.lsp.LSP.connect(LSP.java:388)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.Main.main(Main.java:35)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "Caused by: java.lang.reflect.InvocationTargetException\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:109)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat java.base/java.lang.reflect.Method.invoke(Method.java:580)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.source.util.Trees.getJavacTrees(Trees.java:92)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\t... 11 more\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "Caused by: java.lang.ClassCastException: class com.sun.tools.javac.util.RichDiagnosticFormatter cannot be cast to class com.sun.tools.javac.util.AbstractDiagnosticFormatter (com.sun.tools.javac.util.RichDiagnosticFormatter and com.sun.tools.javac.util.AbstractDiagnosticFormatter are in module jdk.compiler of loader 'app')\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.util.RichDiagnosticFormatter.<init>(RichDiagnosticFormatter.java:99)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.util.RichDiagnosticFormatter.instance(RichDiagnosticFormatter.java:93)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.main.JavaCompiler.<init>(JavaCompiler.java:475)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat org.javacs.ReusableCompiler$ReusableContext$ReusableJavaCompiler.<init>(ReusableCompiler.java:248)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.util.Context.get(Context.java:149)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.main.JavaCompiler.instance(JavaCompiler.java:125)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.model.JavacElements.<init>(JavacElements.java:111)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.model.JavacElements.instance(JavacElements.java:104)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.api.JavacTrees.<init>(JavacTrees.java:209)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.api.JavacTrees.instance(JavacTrees.java:196)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat jdk.compiler/com.sun.tools.javac.api.JavacTrees.instance(JavacTrees.java:183)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\tat java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)\n"
2026-01-15T09:26:46.218 helix_lsp::transport [ERROR] jls err <- "\t... 13 more\n"

Environment info:

$ mvn -v
Apache Maven 3.9.12 (848fbb4bf2d427b72bdb2471c22fced7ebd9a7a1)
Maven home: /home/gert/.local/share/mise/installs/maven/3.9.12/apache-maven-3.9.12
Java version: 21.0.2, vendor: Oracle Corporation, runtime: /home/gert/.local/share/mise/installs/java/21.0.2
Default locale: en, platform encoding: UTF-8
OS name: "linux", version: "6.14.0-1019-oem", arch: "amd64", family: "unix"

Thanks for this project, I'm really hoping for it to become a more stable/transparent alternative to jdtls!

[gertvv]

Example of where this happens: https://bitbucket.org/ikmd/sof-data-transfer/src/08666d2e3550e4b50dd0945d15516703bde74a35/?at=feature%2Fpivot (note it depends on a local install of the maven artifact produced by https://bitbucket.org/ikmd/sof-schema/src). The LSP works on e.g. Utils.java but crashes with the above error on e.g. GradeProFileExtractor.java

[alepekhin]

What element hover did you try? For me it shows hover at least for some

[gertvv]

Interesting, now I've done an LSP restart with that file open. Hover and go-to-definition are working now within this file. I will explore a bit more to see if/when it crashes again.

[gertvv]

Ah, sorry, in GradeProTransformer it crashes immediately on restart. I think I got them mixed up.

[alepekhin]

The same after restart. But I confirm this error may happen somehow. I saw it earlier in one of my project

[gertvv]

That's definitely not working for me. Any pointers as to what to try? Should I try installing a development version, a different JDK, ...?

[gertvv]

Oh it seems you're on master, I'm on the feature/pivot branch.

[alepekhin]

I use the latest jls version from master branch
Other env

alepekhin@home:~/Downloads/ikmd-sof-data-transfer-eee999ced1dc$ mvn -version
Apache Maven 3.9.11 (3e54c93a704957b63ee3494413a2b544fd3d825b)
Maven home: /home/alepekhin/bin/apache-maven-3.9.11
Java version: 21.0.2, vendor: Oracle Corporation, runtime: /home/alepekhin/bin/jdk-21.0.2
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "6.8.0-90-generic", arch: "amd64", family: "unix"

alepekhin@home:~/Downloads/ikmd-sof-data-transfer-eee999ced1dc$ vim -version
VIM - Vi IMproved 9.1 (2024 Jan 02, compiled May 3 2025 09:58:55)

with vim-lsc plugin

Nothing special...

[gertvv]

OK I could try building jls from master.

What I was also saying, for me the issue occurs on the feature/pivot branch of sof-data-transfer, not on the master branch there.

[alepekhin]

When you switch to jls master branch execute

export JLS_LOG_LEVEL=OFF

before jls start. It did not work for me without that

[gertvv]

It seems to work on master, although I needed one lsp-restart after first project load.