Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

Client message serialization fails, language server is never initialized

Open
  • Is something wrong?
#438 1 comment 1 reaction 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
emacs-lisp
Domain
devtools

Research direction

Start with the initialization path in lsp-mode.el around line 7646 and the lsp-java-format-tab-size definition shown in the issue. Reproduce by connecting a Java buffer to the language server with the reported Emacs setup, then trace the serialization failure involving set-from-style. Done means the initialize request is serialized and sent without the json-value-p error.

Written by the indexing model from the issue text.

Description

Describe the bug
The client message to initialize the language server is not sent because an error occurs during serialization:
LSP :: Sending to process failed with the following error: Wrong type argument: json-value-p, set-from-style

From what I could see, this happens when lsp-mode tries to initialize.

The variable lsp-java-format-tab-size uses 'c-basic-offset that has 'set-from-style as default value.

(lsp-defcustom lsp-java-format-tab-size 'c-basic-offset
  "The basic offset"
  :type 'symbol
  :lsp-path "java.format.tabSize")

Setting 'c-basic-offset to a number prevents the serialization error.

I am getting this error in my linux machine only, with latest emacs from git.
GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, cairo version 1.17.8) of 2023-05-23
Note: I don't remember getting the same error in emacs 28 so I suspect it might be specific to emacs 30.

lsp-java version:
Version: 20230507.517
Commit: https://github.com/emacs-lsp/lsp-java/commit/961f1a13e3db9a6b395584be99ef9572bb414e63

To Reproduce
Try to connect any java buffer to the language server.
Server process starts, but never receives the initialize request.

Expected behavior
The language server is initialized.

Logs

LSP :: Restarting LSP in buffer App.java
using config for config_linux
LSP :: Sending to process failed with the following error: Wrong type argument: json-value-p, set-from-style
LSP :: Connected to [jdtls:899939/starting /home/i2n/code/test].
Dominant language
Emacs Lisp
Stars
696
Forks
97
No merged PRs in 30d

Getting set up

This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from emacs-lsp/lsp-java

All issues in emacs-lsp/lsp-java

Similar issues

More DevTools issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.