Bad performance sass compared to sassc

[matiskiba]

Hello,

Since the deprecation of libsass I'm looking into transitioning to dart sass. For that I'm looking into performance issues.
I've encountered a case where sassc takes 200ms compared to libsass taking 2s. Is that interesting for you? should I post the files? (there are many files in this use case)

King regards,
Mati

[jathak]

What method did you use to install Dart Sass? If you're using NPM, you're getting the compiled-to-JS version, which has an unavoidable performance hit, but if you've installed it through some other method (the standalone release on GitHub, Homebrew, Pub, etc), this is something we could take a look at.

[nex3]

It's worth noting that 2s versus 200ms is a much larger performance hit than we'd expect, but much of that may be caused by details like how you're running Sass. As @jathak says, to provide you with more help we need a lot more information about how you installed Sass, how you're running it, and what your CSS looks like.

[matiskiba]

I've downloaded the release dart-sass-1.32.0-linux-x64.tar.gz
Ran the following commands

#1: time sass --update ../test.scss -I /var/www/cp/xsites_versions/connector_js_mati > res.css
#2: time sassc ../test.scss -I /var/www/cp/xsites_versions/connector_js_mati > res.css

The timings of sass are: "user" avg 450-500ms
The timings of sassc are: "user" avg 250ms

So about x2 performance hit.

[matiskiba]

Update: I ran the dart sass command line wrongly. This is the relevant command:
#1: time sass ../test.scss -I /var/www/cp/xsites_versions/connector_js_mati res.css

And this is the output:
real 0m2.140s
user 0m3.100s
sys 0m0.104s

A 10x performance hit

@nex3 @jathak

[nex3]

Again, without knowing what your stylesheet looks like, we can't provide much information about why it's taking so much time to compile.

[nullishamy]

Hi there. I'm maintaining catppuccin/gtk, and we have experienced this among other problems when trialling a migration to dart-sass (documented @ catppuccin/gtk#224 (comment)).

Happy to open a new issue if you wish to track a fix there. Just popping in so you can investigate a real-work complete repo that experiences this issue, as indicated by the request for more info on the topic.

[nex3]

@nullishamy I don't have a nix setup. Can you provide me with a standalone set of Sass inputs that I can test against?