Replacing Bower with "guix environment"

[Christopher Allan Webber]

Hello all,

I'm interested in "guix environment" as a universal solution for
virtualenv/bower/etc.  There's good reasons to want this; aside from
Guix being awesome, packaging for web applications is getting more and
more insane and often involves many layers of package management, often
*multiple language package managers at once*.  It's a sad state of
affairs.  Why not have a universal solution?  "guix environment" could
be that, I hope?  But there are some challenges.

The virtualenv side (having libraries set up for development on the
Python end) is really easy with "guix environment" assuming those files
are there: you have your PYTHONPATH set up, done.

But the "bower" side of things is not so easy.  Most web applications
need to serve many assets to the browser: javascript like jquery, css
like bootstrap, fonts like fontawesome or really any other
fonts, not to mention any icon sets, etc.  Web applications need to
serve these in both a "development" way, usually using some simple
development server, in which case these have to be easily discovered and
served.  For production, these need to be served by
nginx/apache/whatever.  Describing to users how to deploy web
applications tends to be pretty hard, so for this last one you want to
make the configuration requirement as much of a one-liner as possible.
This usually means then that the static assets (jquery, fonts, etc) are
referenced from somewhere inside the package, usually in an extlib/
directory or such.

There are two common ways to do this:

 - The "classic" method of doing this is pretty gross: just check all
   those assets directly into your project, maybe in some sort of
   "extlib/" directory.  I don't need to tell guix-devel just how bad of
   a solution this is!  And yet, most web developers (including me
   *shameface*) have done it, even in our free software projects.

 - The "hip new way" of doing things is to use Bower.  Bower is a
   package manager, but it's made specifically for static assets served
   to the user, such as css files, fonts, javascript like jquery, etc.
   Bower also puts these in an extlib/ or whatever, but it puts them in
   that place *for* you.

It's possible in Guix or Debian packages or whatever to rely on a system
installed jquery or etc, just a minor pain in the butt, linking in the
jquery packages and etc manually into that extlib place during building
the package/derivation.  Okay, not so bad.

But what about "guix environment", where we're directly checked out
inside the package?  What we want to do is this:

  ~/devel/mediagoblin/$ guix environment -l package.scm

And this will set up the python dependencies for sure, and maybe it can
even install the jquery package and stuff, but if I run:

  # put your dev server command here
  ~/devel/mediagoblin/$ ./lazyserver.sh

Oh no!  jquery is installed, but it's not linked into extlib/jquery/
where I expected it.  So suddenly I'm looking at my development instance
and none of my javascript is working and I'm very confused!

It could be that we have jquery packaged, that it's in my
~/.guix-profile/ or etc, but my application doesn't know about it.  This
is "guix environment" for development, so there's no munging the package
during install, I'm hacking *in* the project.

So what can we do?  I still think serving an extlib/ directory or some
easily findable directory is the best way to keep deployment clean, and
anyway, "guix package" can handle setting up the symlinks for that, it's
just "guix environment" that has no way to play along.

What can we do?  My first reaction on IRC is that "maybe there could be
some sort of hook that's run after 'guix environment' that could link
these things into the package".  This was not well received, and for
good reason: it makes "guix environment" non-functional.

Dave Thompson has made what I think is probably a good suggestion: there
should be some sort of environment variable set with something
searchable.  This way, during the "./configure --link-extlib && make" or
"python setup.py develop" or whatever such setup-for-development
process, there's a way to see, aha here's the jquery, symlink that here;
here's the font-awesome, symlink that here; here's the bootstrap,
symlink that here...

I don't know what this environment variable would be called.
WEB_ASSETS_PATH?  The other tricky thing is, it's easy to say "put CSS
files and jquery in that thing", but what about fonts?  Those have
their own location already.  Should both be added to the path?

Anyay, I'd love to have a way to do this with Guix.  If someone can find
a nice solution, I'll make it an option for development with GNU
MediaGoblin instead of using virtualenv/bower. ;)  But we need to know
the right path first!

Looking forward to your ideas,
 - Chris