CSS modules scoped and global class name selectors aren't combined when minified

[elliotwaite]

This:

.a {
    color: red;
}

.b {
    color: red;
}

:global(.c) {
    color: red;
}

:global(.d) {
    color: red;
}

minifies to this:

._8Z4fiW_a, ._8Z4fiW_b {
  color: red;
}

.c {
  color: red;
}

.d {
  color: red;
}

But I expected it to minify to this:

._8Z4fiW_a, ._8Z4fiW_b, .c, .d {
  color: red;
}

Demo:

use lightningcss::{
    css_modules,
    stylesheet::{MinifyOptions, ParserOptions, PrinterOptions, StyleSheet},
};

fn main() {
    let mut stylesheet = StyleSheet::parse(
        r#"
.a {
  color: red;
}

.b {
  color: red;
}

:global(.c) {
  color: red;
}

:global(.d) {
  color: red;
}
"#,
        ParserOptions {
            css_modules: Some(css_modules::Config::default()),
            ..ParserOptions::default()
        },
    )
    .unwrap();

    stylesheet.minify(MinifyOptions::default()).unwrap();
    let css = stylesheet.to_css(PrinterOptions::default()).unwrap();

    // The scoped class name selectors get combined, but the global class name
    // ones don't.
    let expected = r"._8Z4fiW_a, ._8Z4fiW_b {
  color: red;
}

.c {
  color: red;
}

.d {
  color: red;
}
";
    assert_eq!(css.code, expected);

    // As a workaround, I can create a separate style sheet and minify that to
    // combine the scoped and global class name selectors into a single rule.
    let mut stylesheet_2 = StyleSheet::parse(&css.code, ParserOptions::default()).unwrap();
    stylesheet_2.minify(MinifyOptions::default()).unwrap();
    let css_2 = stylesheet_2.to_css(PrinterOptions::default()).unwrap();
    let expected_2 = r"._8Z4fiW_a, ._8Z4fiW_b, .c, .d {
  color: red;
}
";
    assert_eq!(css_2.code, expected_2);
}