bug#55278: 29.0.50; OSM package

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Stallman <rms@gnu.org>
> Date: Thu, 05 May 2022 14:38:18 -0400
> 
> 
> I did M-x osm-search RET London RET
> just after starting the package, and I got an error
> that function json-parse-string is undefined.
> 
> None pf the Lisp sources in my checkout defines that function.
> Is it in some ELPA package?

No, it's implemented in json.c in the Emacs sources.  But to have that
function defined, you need to build Emacs with libjansson, which is an
optional dependency of Emacs.  The OSM package says in its README:

  The package is available on GNU ELPA and can be installed with =package-install=.
  Note that osm.el requires Emacs 27 and depends on the external =curl= program.
  Emacs must be built with libxml, libjansson, librsvg, libjpeg and libpng
  support. The following is an example configuration which relies on =use-package=.
  Please take a look at the [[https://github.com/minad/osm/wiki][wiki]] for additional configuration.

So it looks like you must to have those optional libraries installed
and you must build Emacs with them, in order to use OSM.