Exposing internal code in eclipse.jdt.ls for extension

[trancexpress]

Hi all,

I'm trying out eclipse.jdt.ls for supporting projects with mixed Java and Xtext based DSLs - so VS Code can be used to write code in our product. I had to modify several places in the code, with a tendency to need to modify more code.

What are the JDT LS committers views on making internal code more extensible? Are PRs that open internal code for extension welcome, or should we fork and modify the code instead?

To give a concrete example of my changes so far: trancexpress@1c0cc98

Best regards and thanks,
Simeon

[fbricon]

On principle, it's ok to request the code to be more extensible, but that's usually for the benefit of writing jdt.ls extensions. My understanding of your changes is you basically need to run a 2nd instance of jdt.ls, one tailored for xtext+java. But in this case, users would basically double the memory/cpu usage if both vscode-java and your extension were installed. Did I understand correctly?

[trancexpress]

My understanding of your changes is you basically need to run a 2nd instance of jdt.ls, one tailored for xtext+java

Not quite, our projects are Eclipse projects with the Java nature and an Xtext builder on top. So whenever the build runs for a project, both Java and DSL code is compiled. Our intent is to let JDT LS support all the DSL languages and Java in one language server process.

Using JDT LS, already our projects are built. For our DSLs we are missing content assist (customizing CompletionHandler) and problem propagation (WorkspaceDiagnosticsHandler). We will need more functionality, such as refactor renaming files, but its hard for me to say what we'll need to adjust for that. We also must adapt vscode-java code for some of the functionality, but that is another topic.

On principle, it's ok to request the code to be more extensible, but that's usually for the benefit of writing jdt.ls extensions.

By extensions here you mean adding more functionality for JDT LS?

We plan to write our own set of plug-ins, that extend JDT LS code to adjust functionality as necessary. The Eclipse application started by vscode-java would be one that extends LanguageServerApplication, the plug-in would extend JavaLanguageServerPlugin and so on. We would like to re-use as much from JDT LS as possible, for that we need a few places to hook our code.

[trancexpress]

Lets continue the discussion with actual code changes: #3719

We will need a few more changes than this, even for our starting prototype. But I've made an initial PR to see how such changes are received.