Contribute validation rules from an external extension

[ydaveluy]

Hi,

I would like to know how it is possible to enrich an existing Langium VSCode extension with new validation rules defined in an other VSCode extension ?

[msujew]

Hey @ydaveluy,

you mean like a linter extension? In VS Code, you can expose an API of your extension if you return something in the activate function of your extension. See the documentation of VS Code on this topic. Therefore, it could be possible to register a validation for the language in a different extension.

However, since the Langium language server lives in a separate process from the extension, it's rather difficult to get the AST for the validation to run. So I'd say it's theoretically possible, but technically challenging to realize due to the process gap between the VS Code extension and the language server.

[ydaveluy]

Hey @msujew,

I was thinking about validation rules depending on the AST.

From my understanding it seems very challenging: it would means sending the serialized AST from langium to the extension, processing validation rules on the de-serialized AST then serializing diagnostics to send then back to langium using a custom request.

An other idea:

On Langium server side provide a custom request such as my_langium_language/registerExtension with the path of the extension module as parameter. Dynamically import the module using the provided path then call a pre-defined function such as registerExtension(services: MyDslSharedServices).

On the extension side it would mean to retrieve the Langium VSCode extension and send the my_langium_language/registerExtension with the path of a module providing registerExtension(services: MyDslSharedServices).

[msujew]

Sure, something like this should work pretty well 👍