DiagnosticsProvider

[ejfasting]

Hello,

I have created a language with langium, and am using it from another LSP server.
It works great to forward requests to langium for completionItems:
const langiumDocument = shared.workspace.LangiumDocumentFactory.fromTextDocument(textDocument); \n const params = { textDocument: document, position: position }; \n const result = await langium.lsp.CompletionProvider?.getCompletion(langiumDocument, params, token);

But there seems to be no "DiagnosticsProvider", and I was wondering how Langium does this behind the scenes?
After tracing the communication between client and server it looks like the client notifies langium with a 'textDocument/didChange'-event, and then langium does 'magic' and forces a 'textDocument/publishDiagnostics' ?

So, to summarise, is there a way for langium to give me the Diagnostics, so that i can forward/provide it myself through my own LSP server?

//Eivind

[msujew]

Hey @ejfasting,

All instances of LangiumDocuments have their respective diagnostics attached to them (in the diagnostics field). However, for those to actually be filled, you need to go through the document lifecycle by calling DocumentBuilder#build on the document.

Note that Langium uses a few performance optimization internally so that documents don't need to be recomputed on every invocation of an LSP service when running inside of the "normal" language server use case. The DocumentBuilder together with the LangiumDocuments service (in tandem with a few other services) will cache data on LangiumDocuments as to minimize the computations necessary. See also this documentation page.

[ejfasting]

Thank you for the feedback @msujew !

I actually dug into your sourcecode to get a little more insight, and ended up with using the DocumentValidator.validateDocument(langiumDocument), which gives me the Diagnostics[] (as you also say).

I'll look at the documentation to fine-tune it.

Thanks again!

//Eivind