Java formatting options provided as initializationOptions.settings.java.format.settings.url are ignored

[HaraldKi]

I wrote already a bug report to eclipse.jdt.ls, mostly to start documenting this somewhat: eclipse-jdtls/eclipse.jdt.ls#3108 , but I get the impression that I misunderstand a concept of configuration of eglot or it may actually be a problem with eglot.

My goal: tell the language server how to format Java.

Somewhat inspired from #888 I do this:

(with-eval-after-load 'eglot
  (add-to-list
   'eglot-server-programs
   `(java-mode
     "jdtls"
     :initializationOptions
     (:settings (:java
                 (:format
                  (:enabled t :profile: "user-variant" :settings (:url "/home/user/.emacs.d/eclipse-formatter.xml"))
                  )
                 ))
     )
   )
  )

• In the EGLOT... buffer I see that these settings are sent to the server
• By adding debug logs to the server, I see that it actually reads and understands the formatter options, all looks dandy. But then eglot does this:

[jsonrpc] e[16:25:17.564] --> textDocument/didOpen {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument ... [clipped]
[jsonrpc] e[16:25:17.626] --> workspace/didChangeConfiguration {"jsonrpc":"2.0","method":"workspace/didChangeConfiguration","params":{"settings":{}}}

The didOpen line is only for context. There is nothing in between. The culprit are the empty "settings" which kills all the nice setup that was sent at initialization time. Basically eclipse.jdt.ls reacts to the empty settings with setting everything back to default.

By setting eglot-connect-hook to nil, because this seems to be the initiator of the didChangeConfiguration, I got what I want, formatting according to the rules provided during initialization.

Question: Am I missing some additional configuration to tell eglot to send the whole java-mode configuration from the initialization phase again. Or is this a misunderstanding between eglot and the server, where the former assumes didChangeConfiguration sends only changes whereas the server assumes it gets the full set of configurations?

Reading https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_didChangeConfiguration it says:

interface DidChangeConfigurationParams{
	/**
	 * The actual changed settings
	 */
	settings: LSPAny;
}

which could be interpreted as saying: if we sent empty, nothing was changed. Yet the ecplise.jdt.ls takes this as a request to "clear" all settings (back to default).
I'll add these findings to the server issue too, but if someone feels strongly about which interpretation is correct and why I would be grateful for a statement.

[HaraldKi]

jdt.ls deviates from the spec here.
eclipse-jdtls/eclipse.jdt.ls#3108 (comment)

So I have to live with

(setq eglot-connect-hook nil)

which works at least at startup. After configuration changes I need to restart the server then. I hope this is workable for a while.

I'll close this sometime soon or anyone with the keys to the empire close it if there is nothing more to say.

[manuel-uberti]

Are you doing that setq globally? I am asking because it will set eglot-connect-hook for every server if you do it that way.

If that is a problem for you, I suggest something along the following lines:

(defun my-do-not-signal-didChangeConfiguration ()
  (remove-hook 'eglot-connect-hook #'eglot-signal-didChangeConfiguration t))

(add-hook 'java-mode-hook #'my-do-not-signal-didChangeConfiguration)

[HaraldKi]

Shortly I want to connect to the typescript compiler too and I was already wondering how to avoid the global setting then. So great hint, as it saves me some digging.