Type support for external lexicons

[tylersayshi]

Support some cli flow that downloads the json for external lexicons used, generates the typescript implementation, then uses that to infer types for the rest of the lexicon definitions.

help welcome for this, otherwise I'll get around to it at some point

[jphastings]

Hey Tyler, I've been poking around with this, and I can't find an approach that feels comfortable to use. Have you had any thoughts?

The closest I got was to allow ref to accept a lexicon object as well as a string ref. I liked this, cos it meant other tools (eg. goat) can manage the lexicons, and the typescript can just use what's there:

import strongRef from "./lexicons/com/atproto/repo/strongRef.json" with { type: "json" };

const like = lx.lexicon("app.bsky.feed.like", {
	main: lx.record({
		key: "tid",
		record: lx.object({
			// Here's the new bit; 'def: main' is assumed, if not specified
			subject: lx.ref(strongRef, { def: 'main', required: true }),
			createdAt: lx.string({ required: true, format: "datetime" }),
		}),
	}),
});

type Like = (typeof like)["~infer"];

const rec: Like = {
	$type: "app.bsky.feed.like",
	subject: {
		$type: "com.atproto.repo.strongRef",
		cid: "bafyreigae3c73ufevrsld6bsloontd7rgb2hb35uszgdiw4vs4sxags4ju",
		uri: "at://did:plc:ephkzpinhaqcabtkugtbzrwu/app.bsky.feed.post/3mjhg2o65hc27",
	},
	createdAt: new Date().toISOString(),
};

console.log(like.validate(rec));
// {
//   success: true,
//   value: {…}
// }

But I can't figure out any way to prevent type widening on the ref'd lexicon — I kept losing all prototypey's delicious type helpers within subject — making it a little bit pointless.

Did you have an approach in mind?