gjs 1.49 / mozjs52 transition

[Jeremy Bicha]

Hi,

Here's my proposed plan for doing the mozjs52 transition. I'd like to
do this transition this week.

1. Upload gjs 1.49.90 to artful.

2. Because gjs 1.49 has different behavior than 1.48, we are bumping
the library name from libgjs0f to libgjs0g. An Archive Admin is needed
to approve the new package and promote mozjs52 to main.

3. Upload the 3 packages that directly depend on libgjs0f so that they
can build against the new library. These are sushi 3.24, polari
3.25.90 and gnome-shell 3.24 (with some backported patches). These
packages are staged at
https://launchpad.net/~jbicha/+archive/ubuntu/temp20170810/+packages

4. An Archive Admin will also need to remove gjs/s390x to complete the
transition (more details below).

5. mozjs38 can be demoted to universe. (Cinnamon might be using mozjs38 soon.)

s390x
====
The gjs 1.49.90 package does not build on s390x. It appears that it is
because mozjs52 does not run on s390x.
https://bugzilla.gnome.org/786180

We already ignored tests failures for mozjs38 on s390x and we've
ignored autopkgtest failures for s390x since gjs 1.48 (GNOME 3.24 for
17.04). Also, Firefox 45 builds on s390x but it stopped building there
sometime since. Because mozjs is the SpiderMonkey JavaScript engine
from Firefox ESR, it is not too surprising that it is broken now.

I believe there's a high probability that gjs already does not work on
s390x and I don't think we are interested in devoting much time or
effort to ensure that GNOME Shell runs on that platform. Therefore, I
recommend that we remove gjs from s390x.

There are several rdepends that will need to be removed from s390x.
And I think we want to stop building the ubuntu-desktop metapackage
for s390x.

Other Info
=======
Apps running the new gjs emit lots of warnings (most of them are
warnings to use 'var' to define variables that are accessed
externally). Hopefully, these will be cleaned up by the time GNOME
3.26 is released.

Philip Chimento, the gjs maintainer presented these slides at GUADEC
if you're interested in what's new for developers in the new version.
https://ptomato.wordpress.com/2017/07/30/modern-javascript-in-gnome-guadec-2017-talk/

The gnome-shell 3.26 update will be coordinated and discussed separately.

Thanks,
Jeremy Bicha