Capture LSP traces per language server and write them to a log file

[dessina-devasia]

Required a mechanism to capture LSP traces for each individual language server and persist them into log files.

Currently, trace output is only visible in the Language Server Console, which makes debugging intermittent failures difficult - especially in CI environments. Capturing and exporting the traces would help with root-cause analysis and reproducibility of issues.

[angelozerr]

I suggest that you use the existing LanguageServerLifecycleManager (it is not an API but for test I think you could use it).

In your test, you could register your listener in test setup:

Project project = ...;
TracingMessageConsumer tracing = new TracingMessageConsumer();
var listener =  new LanguageServerLifecycleListener() {
    @Override
    public void handleStatusChanged(@NotNull LanguageServerWrapper languageServer) {
        
    }

    @Override
    public void handleLSPMessage(@NotNull Message message, @NotNull MessageConsumer messageConsumer, @NotNull LanguageServerWrapper languageServer) {
        String lspTrace = tracing.log(message, messageConsumer, ServerTrace.verbose);
        // Write lspTrace in a file
    }

    @Override
    public void handleError(@NotNull LanguageServerWrapper languageServer, @NotNull Throwable exception) {

    }

    @Override
    public void dispose() {

    }
};
LanguageServerLifecycleManager.getInstance(project).addLanguageServerLifecycleListener(listener);

and remove the listener at the end

LanguageServerLifecycleManager.getInstance(project).removeLanguageServerLifecycleListener(listener);