Is it possible to add completion items to a Microsoft Language Server in runtime? - intellij-plugin

Question

I am trying to develop a IntelliJ plugin which provides a Language Server with help of lsp4intellij by ballerina.
Thing is, i've got a special condition: The list of completion items should be editable in runtime.
But I've not found any way to communicate new completionItems to the LanguageServer process once its running.
My current idea is to add an action to the plugin which builds a new jar and then restarts the server with the new jar, using the Java Compiler API.
The problem with that is, i need to get the source code from the plugin project including the gradle dependencies accessable from the running plugin... any ideas?

Answer 1

If your requirement is to modify the completion items (coming from the language server) before displaying them in the IntelliJ UI, you can do that by implementing the LSP4IntelliJ's
LSPExtensionManager in your plugin.
Currently, we do not have proper documentation for the LSP4IntelliJ's extension points but you can refer to our Ballerina IntelliJ plugin as a reference implementation, where it has implemented Ballerina LSP Extension manager to override/modify completion items at the client runtime in here.

Answer 2

For those who might stumble upon this - it is indeed possible to change the amount of CompletionItems the LanguageServer can provide during runtime.
I simply edited the TextDocumentService.java (the library I used is LSP4J).
It works like this:
The main function of the LanguageServer needs to be started with an additional argument, which is the path to the config file in which you define the CompletionItems.
Being called from LSP4IntelliJ it would look like this:
String[] command = new String[]{"java", "-jar",
"path\\to\\LangServer.jar", "path\\to\\config.json"};
IntellijLanguageClient.addServerDefinition(new RawCommandServerDefinition("md,java", command));
The path String will then be passed through to the Constructor of your CustomTextDocumentServer.java, which will parse the config.json in a new Timer thread.
An Example:
public class CustomTextDocumentService implements TextDocumentService {
private List<CompletionItem> providedItems;
private String pathToConfig;
public CustomTextDocumentService(String pathToConfig) {
this.pathToConfig = pathToConfig;
Timer timer = new Timer();
timer.schedule(new ReloadCompletionItemsTask(), 0, 10000);
loadCompletionItems();
}
#Override
public CompletableFuture<Either<List<CompletionItem>, CompletionList>> completion(CompletionParams completionParams) {
return CompletableFuture.supplyAsync(() -> {
List<CompletionItem> completionItems;
completionItems = this.providedItems;
// Return the list of completion items.
return Either.forLeft(completionItems);
});
}
#Override
public void didOpen(DidOpenTextDocumentParams didOpenTextDocumentParams) {
}
#Override
public void didChange(DidChangeTextDocumentParams didChangeTextDocumentParams) {
}
#Override
public void didClose(DidCloseTextDocumentParams didCloseTextDocumentParams) {
}
#Override
public void didSave(DidSaveTextDocumentParams didSaveTextDocumentParams) {
}
private void loadCompletionItems() {
providedItems = new ArrayList<>();
CustomParser = new CustomParser(pathToConfig);
ArrayList<String> variables = customParser.getTheParsedItems();
for(String variable : variables) {
String itemTxt = "$" + variable + "$";
CompletionItem completionItem = new CompletionItem();
completionItem.setInsertText(itemTxt);
completionItem.setLabel(itemTxt);
completionItem.setKind(CompletionItemKind.Snippet);
completionItem.setDetail("CompletionItem");
providedItems.add(completionItem);
}
}
class ReloadCompletionItemsTask extends TimerTask {
#Override
public void run() {
loadCompletionItems();
}
}
}