eldoc signatures still not working in Java

[sdhoward]

Describe the bug

I have Emacs 29.3 on MacOS, and lsp-java 20240524.2207 installed from Melpa.

Within the past year, perhaps in an older Emacs or an older lsp-mode, the type signature of the Java variable or method would appear, in the fixed-pitch font, in the minibuffer, when the cursor was over the function name. There was no mouse hovering or UI involved.

In fact, I still have this behavior in lsp-mode for Golang variables and functions. A screenshot is attached. If I set lsp-eldoc-enable-hover to nil, the behavior in Golang mode becomes disabled. So I think this feature is related to eldoc.

I read one recent bug report and I installed the fixed version that was released and it's not resolving my issue.

Please help to point out which setting re-enables this, or whether a regression has appeared. Thanks.

To Reproduce

The simple init.el that I use to reproduce this is:

(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
(package-initialize)

(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(package-selected-packages '(go-mode lsp-java)))
(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )

Screenshots

^ the signatures appear in go-mode but not java-mode

[Horrih]

I am encountering this issue as well.

Turning off textDocument/hover dynamicRegistration works around the issue

I investigated a bit, comparing eglot (where it works)/lsp-mode (where is does not) : The main difference I saw was that lsp-mode declares textDocument/hover with dynamicRegistration: true where as eglot sets it to nil.

Setting this in lsp-mode.el : `lsp--client-capabilities()' to t seems to fix the issue for me.

 (hover . ((contentFormat . ["markdown" "plaintext"])
               (dynamicRegistration . nil)))

Speculation for a durable fix.

My guess would be that with dynamic registration, lsp-mode is notified too late that the server supports hover.

lsp-mode seems to enable eldoc at startup only, when `lsp-managed-mode' is turned on.

(when (lsp-feature? "textDocument/hover")
      (add-hook 'eldoc-documentation-functions #'lsp-eldoc-function nil t)
      (eldoc-mode 1))

With dynamic registration, I guess it would have to be turned on when receiving the message instead of at startup time ?

@yyoncho , would you have some advice on how to proceed with this ?

[sdhoward]

I appreciate the workaround. I edited the file in my melpa directory and byte-compiled it again. Works well.

I forgot to include which version of jdtls I'm on - right now it's 1.37.0. I don't know which version I had when it was working. Did the behavior change from a previous version of jdtls?