Introduce $kind as a pivot point for uncaught errors

[blast-hardcheese]

Why

$kind is emerging as a de-facto property to identify the type of a payload. Adding a literal $kind: "error" permits consumers to easily filter in/out error payloads.

What changed

Add $kind: "error" to RiverUncaughtSchema, for consumers to easily identify error payloads

Versioning

• Breaking protocol change
• Breaking ts/js API change

[jackyzha0]

code already exists for this purpose, all new user defined errors also define their own code to discriminate on

https://github.com/replit/river/blob/main/router/result.ts#L14

[blast-hardcheese]

Classifiers are useful, since code idiomatically means the actual value to match on, not that the structure represents an error more broadly.

[jackyzha0]

if its ok: false then its an error, is there anything else in particular you're trying to assert?

[blast-hardcheese]

Ahh. The issue I was running into was that the python codegen doesn't expose ok, and the results of the client operations are just an otherwise inscrutable R | E. Bummer.

[blast-hardcheese]

Alright. Going with a different approach.