From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?utf-8?Q?Ludovic_Court=C3=A8s?= <ludo@gnu.org>
Subject: Migrating to Guile-JSON 3.x
Date: Tue, 22 Jan 2019 14:46:30 +0100
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To: guix-devel@gnu.org

Hello Guix!

As you may know, Guile-JSON 3.x, released a couple of weeks ago, makes
significant incompatible API changes, the most important of which is
this:

--8<---------------cut here---------------start------------->8---
$ guix environment --ad-hoc guile guile-json@1 -- guile -c '(use-modules (j=
son)) (pk (json-string->scm "{ \"a\": 1, \"b\": 2 }"))'

;;; (#<hash-table 10af420 2/31>)
$ guix environment --ad-hoc guile guile-json@3 -- guile -c '(use-modules (j=
son)) (pk (json-string->scm "{ \"a\": 1, \"b\": 2 }"))'

;;; ((("b" . 2) ("a" . 1)))
--8<---------------cut here---------------end--------------->8---

In addition, JSON lists are now vectors in Scheme:

--8<---------------cut here---------------start------------->8---
$ guix environment --ad-hoc guile guile-json@1 -- guile -c '(use-modules (j=
son)) (pk (json-string->scm "[ 1 2 3 ]"))'

;;; ((1 2 3))
$ guix environment --ad-hoc guile guile-json@3 -- guile -c '(use-modules (j=
son)) (pk (json-string->scm "[ 1 2 3 ]"))'

;;; (#(1 2 3))
--8<---------------cut here---------------end--------------->8---

Conclusions:

  =E2=80=A2 Migration will be tricky since we=E2=80=99ll have to audit all =
our uses.
    Most of our code that uses JSON has unit tests but some of it
    doesn=E2=80=99t, in particular the web interface bindings in (guix ci) =
and
    (guix swh).

  =E2=80=A2 We won=E2=80=99t be able to support both 1.x and 3.x, so it=E2=
=80=99ll be a change
    with no return.

  =E2=80=A2 Things that depend on Guix (Cuirass, GWL, hpcguix-web, etc.) wi=
ll
    have to switch at the same time.

Thoughts?  Volunteers?  :-)

Thanks,
Ludo=E2=80=99.