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

[HaraldKi]

Summary:

Despite providing a formatter specification xml which is actually read and seemingly understood by the language server, formatting does not change from the default.

My setup:

• Emacs eglot (but read on, I checked most things on the language server level)
• On commit 66f98a6 of Wed Mar 20 15:56:53 2024 +0800

What I do:
I configure formatting with an xml file and I see the following things:

At initialization the format specification xml is send by the editor as follows (taken from the editor<->language server logs provided by eglot):

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "processId": 5196,
    "clientInfo": {
      "name": "Eglot",
      "version": "1.17"
    },
    "rootPath": "/home/... some project",
    "rootUri": "file:///home/... same project",
    "initializationOptions": {
      "settings": {
        "java": {
          "format": {
            "enabled": true,
            "settings": {
              "url": "/home/user/.emacs.d/eclipse-formatter.xml"
            }
          }
        }
      }
    },
 ...

I added a log output to FormatterManager.java to verify the file is actually read.

diff --git a/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/FormatterManager.java b/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/FormatterManager.java
index 232040ba..33bd53e2 100644
--- a/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/FormatterManager.java
+++ b/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/FormatterManager.java
@@ -167,6 +167,7 @@ public class FormatterManager {
                        throw new CoreException(new Status(IStatus.WARNING, IConstants.PLUGIN_ID, e.getMessage(), e));
                }
                int version = handler.getVersion();
+    JavaLanguageServerPlugin.logInfo("TTTTTTTTTTTTTTTT " + handler.getSettings());
                if (handler.getSettings() == null) {
                        if (!Objects.equals(profileName, handler.fName)) {
                                JavaLanguageServerPlugin.logError("Invalid settings: java.format.settings.profile=" + profileName + ". The '" + profileName + "' profile doesn't exist.");

The output from this log looks like:

!ENTRY org.eclipse.jdt.ls.core 1 0 2024-03-24 10:02:35.140
!MESSAGE TTTTTTTTTTTTTTTT {org.eclipse.jdt.core.formatter.insert_space_after_ellipsis=insert, org.eclipse.jdt.core.formatter.insert_space_after_comma_in_enum_declarations=insert, org.eclipse.jdt.core.formatter.insert_space_before_comma_in_a...

Further I delete any project_<hexcode> directories from the workspace to force the language server to set up the project freshly. This project has neither a gradle nor maven build. Apart from the formatting it works as expected, in particular compiler errors are shown, etc.

Yet, the formatting rules are clearly not applied.

I'll keep digging, but would be grateful for any hints.

[HaraldKi]

I could verify the following:

• At initialization, eglot sends the the configuration I want and it accepted without problem by the server.
• But then soon after initialization, eglot sends this: workspace/didChangeConfiguration {"jsonrpc":"2.0","method":"workspace/didChangeConfiguration","params":{"settings":{}}}
• The empty settings provided are the reason, afaict, that all server settings are reverted to their defaults.

Is this a mismatch in interpretation what empty settings in didChangeConfiguration mean? Eglot seems to assume that it is OK to send empty settings if in fact nothing has changed. I assume it would send only changed values if there would be a real change. But eclipse.jdt.ls seems to assume that the change message provides not just changes but all settings?

Hints welcome.

[fbricon]

indeed jdt.ls falls back to default settings when receiving an empty object. It expects the full settings. Partials won't be enough.

[HaraldKi]

Now I wonder: is this in accordance with the protocol specification? If I read https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_didChangeConfiguration I would rather interpret this as "send changes", not "send full settings". Though the "specification" is not very formal.

[fbricon]

@HaraldKi I think you're right, jdt.ls deviates from the spec here.