Deriving Json: inline notation no longer supported?

[vouillon]

Describe the bug
An expression [%derive.json: cookie_array] no longer compiles:

File "src/lib/eliom_cookies_base.shared.ml", line 21, characters 28-39:
Error: Deriver json does not support inline notation

Versions
This compiles with Js_of_ocaml 3.4 but not Js_of_ocaml 3.5

[hhugo]

I think the syntax changed a little when we switch to ppxlib (#809)

Try this syntax

[%json: cookie_array] 

[vouillon]

This seems to work, indeed, with the following changes:

before	now
derive.json	json
derive.to_json	json_of
derive.of_json	of_json

[hhugo]

I created #922 to document the syntax a bit.

It also include a change to allow [%to_json] in addition to [%json_of].
This should make the transition easier and also keep some symmetry with names generated from [@@deriving json]

[hhugo]

I've added some documentation for upgrading to 3.5
https://github.com/ocsigen/js_of_ocaml/wiki/Upgrade-from-3.4.0-to-3.5.0

[hhugo]

ocaml/opam-repository#15312