[I've put the related Debian bugreport in the loop]

Hello,

I finally found some time to look into this.

Disclaimer: I don't know much about CSS compression and the mailman3 web interface is the first time that I got into contact with either of sassc and node-less.

TL;DR:

• Hyperkitty doesn't need (or use) less.js/lessc at all. It can safely be removed from COMPRESS_PRECOMPILERS.
• The situation is different with sassc, it's actually used for compressing CSS by hyperkitty. Doing the compression at build-time should be possible but requires more work. I have a plan ;)

Christian Ehrhardt:

I have checked a fully installed mailman3 stack in Debian/Ubuntu and there are only two sources of .less files that we have to be concerned of.

First there is the package fonts-font-awesome which is pulled in on the following path: [...] It seems different for the second case which is libjs-bootstrap from the source package twitter-bootstrap3

I don't think that any of the .less files you're referencing to will be processed by 'django-admin compress' on the mailman3-web project. The .less files are all outside the scope of the mailman3-web project. So I'm pretty sure that the node-less/lessc dependency can safely be dropped immediately.

Moreover, looking at the hyperkitty example_project/settings.py[1], it doesn't even reference the lessc compiler at all. Only settings.py from mailman-suite[2] references it, which probably is a copy-and-paste bug. There's even an open issue about that[3]. Since in Debian we took the mailman-suite settings.py as template, we suffer from this copy-and-paste bug as well.

[1] https://gitlab.com/mailman/hyperkitty/blob/master/example_project/settings.p... [2] https://gitlab.com/mailman/mailman-suite/blob/master/mailman-suite_project/s... [3] https://gitlab.com/mailman/mailman-suite/issues/7

Does anyone know of other uses of .less in the mailman3 stack that I have missed that we would have to think about?

Regarding sassc: Hyperkitty is the only part of the mailman3 stack that uses django-compressor. And apparently there's just one single html template that will be processed by sassc (well, to be precise, all html files that use this template):

/usr/lib/python3/dist-packages/hyperkitty/templates/hyperkitty/base.html

In this file, four CSS files are being compressed and packed together by sassc:

hyperkitty/libs/fonts/icomoon/icomoon.css hyperkitty/libs/fonts/droid/droid.css django-mailman3/css/main.css hyperkitty/sass/hyperkitty.scss

The last one is special as it's a scss file itself and needs to be processed by sassc itself.

OTOH there also is an experimental approach to this, could someone with a dev-stack of mailman3 just remove the node-less package and see if on a normal setup something breaks at all?

I've done this. Result: removing node-less doesn't change anything (which is in line with my assumption that node-less/less.js/lessc is not required/used at all).

On the other hand, removing sassc breaks the setup, even with COMPRESS_OFFLINE being turned on:

CommandError: An error occurred during rendering /usr/lib/python3/dist-packages/django_mailman3/templates/django_mailman3/profile/delete_profile.html: /bin/sh: 1: sassc: not found

Christian Ehrhardt:

On Fri, Mar 15, 2019 at 10:19 AM Jonas Smedegaard <dr@jones.dk> wrote:

...

Quoting Christian Ehrhardt (2019-03-15 06:39:08)

...

On Fri, Mar 15, 2019 at 12:08 AM Abhilash Raj <maxking@asynchronous.in> wrote:

...

On Thu, Mar 14, 2019, at 1:42 PM, Jonas Meurer wrote: Christian Ehrhardt:

...

I was evaluating the Dependencies of mailman3 in Ubuntu and I was wondering if I could cut them down a bit. One thing that got my attention is the dependency from mailman3-web [1] to nodejs for less [2] and ruby-sass [3].

I was wondering if we could by default not install node-less/ruby-sass and what exactly that would imply.

less is a reinvention of sass: It is often adaptable to sass with a simple patch.

Original sass processor was ruby-sass, but nowadays a better processor is sassc. Or if you want to integrated processing with Python then python3-libsass which uses same core library for its processing.

I have not looked closely on mailman3, but I highly doubt there is a real need for dynamic processing of less/sass during runtime.

Yeah I doubt that as well. In the meantime I also found [1] which seems to have come to the same conclusion for the majority of default setups.

For upstream to disable it by default it was mentioned that there is a need for a customize kit which seems fine [1].

There is a further argument to disable the live compressors, at least as I read COMPRESS_OFFLINE that seems helpful for production setups anyway to speed up and safe CPU load.

You're totally right. Therefore, COMPRESS_OFFLINE is already enabled per default in mailman3-web on Debian. The django-admin compress command is executed during package installation and upgrade by the package postinst script.

So while upstream waits until a "customize kit" exists to switch defaults, as a downstream like Debian/Ubuntu I wonder if we already could: pulling it in at runtime

• drop sass/less compilers to a suggest
• disable the live compression in the default config that we ship
• keep the config commented-out to make it easy for admins that want to enable it later
• pre-compress at build time and enable compress_offline for speed
  • maybe call django_admin compress [3][4] or similar at build time?
  • having sass/less as build dependencies seems much safer than

@Jonas M.: what do you think about [2] (again maybe after Buster)? Sorry to not know more of this yet, but I hope suggesting what I think might work helps to get us the right way.

I'm absolutely in favour of getting rid of the sassc runtime dependency. After a chat with Jonas Smedegaard (thanks for his valuable input!), I think that I have an idea and a roadmap on how to get there:

1. Process static/hyperkittysass/hyperkitty.scss with sassc at build- time and patch templates/hyperkitty/base.html to reference the resulting CSS file.
2. Patch base.html at build-time to remove the '{% compress css %}' statements from it.

By then, we already can safely drop the run-time dependency on django-compressor from hyperkitty since it won't be needed anymore and consequently remove sassc dependency from mailman3-web (and all references to django-compressor from settings.py).

The downside will be some performance decrease as hyperkitty pages will reference four separate CSS file instead of a combined one. But that can be addressed as well:

3. Make python3-django-mailman3 a build-dependency of mailman-suite (one of the referenced CSS files is shipped by django-mailman3) and combine all four CSS files into one by runing sassc at build-time.
4. Further patch base.html at build-time to replace the four separate CSS references by one to the resulting combined CSS.

I plan to start working on the actual implementation soon but would be glad to hear your thoughts on it.

Cheers jonas