[Bug]: CSS: @value replacement in keyframes/animation produces broken output

[Knagis]

System Info

rspack 2.2.3

Details

@value replacement for animation + @keyframes produce broken output:

===== input =====
@value animName: pulseAnim;

.anim {
    animation: animName 2s linear;
}

@keyframes animName {
    from { opacity: 0; }
}

===== rspack (native css/module) output =====
.css-modules-value-animation-src_index_css-anim {
    animation: pulseAnim 2s linear;
}

@keyframes css-modules-value-animation-src_index_css-animName {
    from { opacity: 0; }
}

note - webpack native css also has an issue, though with different output: webpack/webpack#22030

Reproduce link

https://github.com/Knagis/rspack-webpack-css-value-animation

Reproduce Steps

npm install
npm run build

[Knagis]

Expected Behavior... Needs to be aligned with webpack.

Likely to keep consistency with how @value are used (not hashed) in selectors:

.anim_hash {
    animation: pulseAnim 2s linear;
}

@keyframes pulseAnim {
    from { opacity: 0; }
}

[intellild]

I checked css-loader and the name is hashed.
localIdentName: "[path][name]__[local]--[hash:base64:5]"

.src-index__anim--aDRCe {
    animation: 2s linear src-index__pulseAnim--rpbwN;
}
@keyframes src-index__pulseAnim--rpbwN {
    0% {
        opacity: 0;
    }
}

I will align with css-loader first.

[Knagis]

css-loader is deprecated now, and it doesn't even support values in selectors that webpack and rspack native css support does support.

/* input */
@value sel: .globalThing;

sel {
    color: blue;
}

/* output */
.XbSZ44YRvgGzLB6rR_A1 {
    color: blue;
}

[intellild]

Emmm, latest webpack emits a warning for re-declaration while the generated name is incorrect.
If we treat at-value and at-keyframes as variable declarations, this is actually correct output.

@value animName: pulseAnim; // <- first declaration

.anim {
    animation: animName 2s linear; // <- deref first declaration here
}

@keyframes animName { // <- declare the second one, the first declaration is shadowed
    from { opacity: 0; }
}

[intellild]

If you want to keep the animation name, at-value is not needed. Just set parser['css/module'].animation = false
https://rspack.rs/config/module-parser#cssautoanimation

[Knagis]

@intellild If the logic that @keyframes override @value holds (why not, seems logical) then would it be expected that for

@value animName: pulseAnim;

@keyframes animName {
    from { opacity: 0; }
}

.anim {
    animation: animName 2s linear;
}

this produces the same output - the animation reference uses the first declaration, not the second.

@keyframes css-modules-value-animation-src_index_css-animName {
    from { opacity: 0; }
}

.css-modules-value-animation-src_index_css-anim {
    animation: pulseAnim 2s linear;
}

Perhaps the better approach is to throw an error when such conflict is encountered to make it explicitly not supported?

I personally don't have clear preference, we don't use this case, it was something that i found while making sure @value for typical cases work for us, and thought it worth reporting - primarily because of the inconsistency with webpack.

[intellild]

Thanks for reporting, this I will add a warning