Better (or configurable) order of built-in transpilation vs custom transforms vs CSS modules

[kizu]

It seems that all current transpilation steps happen before any of the custom transforms, but the renaming of idents from CSS modules happening after custom transforms.

I don't know how viable it is, but the way I'd expect it to work:

1. Entry custom transforms.
2. Built-in transpilation, CSS Modules idents.
3. Exit custom transforms.

This way it would be possible to adjust things both before the built-in transpilation, and after CSS Modules.

Use cases:

1. Using a custom env() visitor to replace it with some value which is then statically transpiled. Example: doing something like color-mix(in srgb, env(--my-color), transparent). Right now this will not transpile the color-mix as it will be done before the custom transforms, even though we could expand the env() into a static color.

2. Adjusting the ident names for CSS Modules. This could allow to work around things like More control over CSS modules dashed-idents naming #315.

If it is not possible to achieve with the custom setup, I wonder what could be the alternatives?