Minifier Breaks Black Translucent Colors

[dev-nicolaos]

Environment

Operating Systems Tested On: Windows 10 Enterprise 22H2, Fedora Linux 40

Node Version: 20.10.0

LightningCSS Version: 1.24.1

Steps to Reproduce

• Clone the reproduction repo
• Run npm ci to install lightningcss
• Run npm run bundle-css

Expected Outcome

All the custom properties in bundled.css will have valid color values as specified in main.css

Actual Outcome

Only the white transparency and red color are output correctly. All the black transparencies have the 0 0 0 before the / in the color function removed (e.g. --Black-60:color(display-p3/.6);) in bundled.css making them impossible for the browser to render.

Notes

I feel confident the issue is with the minifiying step. If you set minify to false in the call to bundle in bundle.js, the output values are valid.

[mischnic]

Playground reproduction

[devongovett]

I think the spec must have changed at some point, but I can't find when. The are a bunch of tests specifically for this.