Providing documentation in the auto-completion popup

[ymc9]

Hi guys,

I'm working on improving the auto-completion experiences of my DSL, and would like to provide richer documentation in the popup window. Like how Prisma does it:

I'm looking at the code of DefaultCompletionProvider but couldn't figure out what's the best way to provide the "documentation" field of CompletionItem. I see there's a DocumentationProvider that I can customize, however the DefaultCompletionProvider doesn't seem to use this service. Are these two services supposed to be connected?

Just wanted to get some confirmation before trying things out more deeply. Thanks 🙏!

[msujew]

Hey @ymc9,

the DocumentationProvider is currently only used by the DefaultHoverProvider as part of the default Langium behavior. It might make sense to adjust the default completion provider to make use of that as well.

Anyway, the best solution for you right now would be to extend the DefaultCompletionProvider and override the createReferenceCompletionItem method. You can then set the documentation field on the returned CompletionValueItem object. Note that you only have an AstNodeDescription in scope of the createReferenceCompletionItem method. You might need to resolve it first. See:

langium/packages/langium/src/references/linker.ts

Lines 203 to 210 in 728b579

	if (nodeDescription.node) {
	return nodeDescription.node;
	}
	const doc = this.langiumDocuments().getDocument(nodeDescription.documentUri);
	if (!doc) {
	return undefined;
	}
	return this.astNodeLocator.getAstNode(doc.parseResult.value, nodeDescription.path);

[alamarche]

I basically did what @msujew proposed above in a concept requirements DSL I was working on. I extended the DefaultCompletionProvider class and leveraged the CompletionItem.documentaton property. Populated it with the same contents that I was passing to the hover provider.

https://github.com/alamarche/reqspec/blob/57acb5089e6d314ca2f8632d26d2290422e1db20/src/language/req-spec-completion-provider.ts#L59C24-L59C24

[ymc9]

Thank you for the quick response @msujew , as always! I'll go ahead with the approach then.

@alamarche your sample looks tremendously helpful 🙏 !