It seems like there's no solutions for generic JSON encoding for OCaml/BuckleScript/Reason either though.
I've worked on various ways to do JSON encoding in Purescript through datatype generics, but the recent RowToList machinery lets us use record types directly. I have a post and some links collected if anyone is interested:
Right, there are some various approaches but I've had a few OCaml users tell me there were some reasons why they weren't/couldn't be used on the front end, sadly. Would really like to see some demos otherwise though
The only JSON encoder / decoder / manipulator that I've seen that is typed and reasonably flexible is Nim's, but even there it's still 5 times more complicated than say Ruby.
[0] https://github.com/mjambon/yojson