Support node ancestors via a configuration option

[remcohaszing]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

You might also support ancestors: https://github.com/vfile/vfile-message#fields

Originally posted by @wooorm in #57 (review)

I looked into ancestors, but I think the information is not relevant here. It makes the messages very verbose. As an end user of the language server, the fact that everything is based on ASTs, is an implementation detail.

Originally posted by @remcohaszing in #57 (comment)

I’m not saying it should be a default. It isn’t in vfile-reporter either.

But I see if quite different. There are many reasons for errors to be thrown. I think users and the code that emits errors should decide whether the positional info and other info in the AST is an “implementation detail” or not.

Originally posted by @wooorm in #57 (comment)

Solution

Add option showAncestors. If this is true, the ancestry will be added to the LSP diagnostic message.

Alternatives

1. showAncestors was chosen arbritrarily. The name could be different.
2. Use DiagnosticRelatedInformation instead of appending to the message. This makes the trace clickable, but it renders differently.

[wooorm]

What about verbose? https://github.com/vfile/vfile-reporter#options, unifiedjs/unified-engine@f44e365

IMO showing URLs here do makes sense, there’s more space here, and there’s links, so you don’t show an entire long ugly URL

[wooorm]

DiagnosticRelatedInformation might be useful for cause? (which are now always shown in vfile-reporter: https://github.com/vfile/vfile-reporter/blob/f8f9655dbaa5f6b8d1d8208a9086363ffc865ce0/lib/index.js#L368-L370).

I’d appreciate an example maybe of how the “popups” look with different types of info and settings, maybe it gets crowded quickly?

[remcohaszing]

One example of diagnostic related information is when you make a TypeScript type error in VSCode.

In this screenshot, main.d.ts(115, 5): The expected type comes from property 'character' which is declared here on type 'Position' is a rendered diagnostic related information. I’m not really sure if diagnostic related information is the correct field for such a trace, but it has crossed my mind. I’m not really sure if it’s even ordered.

I like the traceLimit option from vfile-reporter. We could use that, and default to 0.