Using icon libraries cause massive increases to build time

[OiYouYeahYou]

Astro Info

Astro                    v5.0.9
Node                     v23.3.0
System                   Linux (x64)
Package Manager          npm
Output                   static
Adapter                  none
Integrations             none

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

Using icon libraries* increases build times by factors of seconds. The worst culprit being a 3,166,940% increase on page reloads in dev mode

	Build (total time score)	Average Page Load **
Clean	1.57s	5.2 ms
Importing	12.81s	16,4686 ms

I've also raised this issue in 2 icon libraries:

• Build and Dev time by multiples of seconds dzeiocom/lucide-astro#25
• Build and Dev time by multiples of seconds dzeiocom/simple-icons-astro#3

* and probably other types of libs, but I've not tested any others
** User hand refreshed consecutively

What's the expected result?

For the build command, I'm less concerned

For the dev command and single page refreshes, I expect the load time to be sub second, not tens of seconds like the repro and other projects

Link to Minimal Reproducible Example

https://github.com/oy3-archive/astro-dep-perf

Participation

• I am willing to submit a pull request for this issue.

[Firaenix]

I'm hitting this too - seems to be the fault of a new Astro version. I'm still trying to identify which version introduced the slowness.

EDIT: It seems to happen as soon as you go from Astro v4 to Astro v5.
I'm not using lucide-astro but lucide-svelte with the @astrojs/svelte adapter.
In dev mode, I'm getting builds of around 3-6 second per page load that has lucide-svelte icons included. the lucide-svelte JS bundle ends up being around 3.4MB or so

[OiYouYeahYou]

It happens in v4 as well, but the build time inflation is still sub second, so at least tolerable. My personal projects still suffer an intolerable build time bloat though

[ematipico]

I thought we fixed that, but maybe this is another issue. Thank you for reporting

[Firaenix]

Is this something easily worked around with some vite config changes? Or is this something inherent to Astro?

[bluwy]

For dev, since lucide-astro is an astro library that needs to be compiled, it's added by Astro to be transformed by Vite. When Vite transforms the library in dev, it doesn't perform treeshaking so all files are imported and processed by default. You can follow vitejs/vite#8237 for some details, but there's not much possible to fix this for now.

For build, it seems like Rollup will transform all files in the library before taking into account of sideEffects false for treeshaking. So it's not quite possible to skip transforming the unused icons early on without some rollup architecture change.

As a workaround, the library needs to export the icons individually and be imported individually, which understandably isn't a very good solution. Or when Vite & rolldown lands. Otherwise personally I use unocss icons.

[Firaenix]

But seems weird that the build size has suddenly ballooned just from upgrading Astro.
I was having page build times in no more than 100ms and likely even lower, however with the latest version of Astro its reached 3-9 seconds per page, which is just a ridiculous time increase and obviously impacts dev experience.