Support JSON schema validation

[dbarnett]

Would it ever be possible for jsonnet-language-server to detect JSON schemas and use them to empower completion and warnings?

For instance, at the simplest extreme that could mean that if you have a simple jsonnet file with a "$schema" field, code completion could suggest other valid names for top-level JSON field names from the schema for you, and warn if you use a name that's not defined in the schema.

[nogweii]

It would also be nice to support a configuration command to be able to have the editor manually specify the schema in case there isn't a $schema field already.

[adam-azarchs]

Specifying it with a modeline comment similar to how the yaml vscode extension does it could work too.
However, to maximize usefulness you'd want to be able to specify schemas in positions other than the top level, for jsonnet documents which might be defining several other documents.

Having the language server validate the output document(s) sounds relatively straightforward, though mapping errors back to the correct location in the jsonnet might prove difficult. There's a google groups thread about this which might be informative.