Fixes#16725
When using `@reference "tailwindcss";` inside a separate CSS root (e.g.
Svelte `<style>` components, CSS modules, etc.), we have no guarantee
that the CSS variables will be defined in the main stylesheet (or if
there even is one). To work around potential issues with this we decided
in #16676 that we would emit all used CSS variables from the `@theme`
inside the `@reference` block.
However, this is not only a bit surprising but also unexpected in CSS
modules and Next.js that **requires CSS module files to only create
scope-able declarations**. To fix this issue, we decided to not emit CSS
variables but instead ensure all `var(…)` calls we create for theme
values in reference mode will simply have their fallback value added.
This ensures styles work as-expected even if the root Tailwind file does
not pick up the variable as being used or _if you don't add a root at
all_. Furthermore we do not duplicate any variable declarations across
your stylesheets and you still have the ability to change variables at
runtime.
## Test plan
- Updated snapshots everywhere (see diff)
- New Next.js CSS modules integration test
This PR fixes an issue when trying to resolve plugins with `exports` in
their `package.json`, like `@headlessui/tailwindcss`. The missing
`conditionNames` in the enhanced resolver config would cause it to not
properly look up the name.
## Test Plan
I added a test using the `postcss` setup (the existing plugin tests are
inside the CLI setup but the CLI can only ever run in Module JS mode).
To ensure the tests are resolving to the right environment (CJS vs MJS),
I added logging of the `import.meta.url` value to the resolver code.
When run, this was the output:
Co-authored-by: Adam Wathan <adam.wathan@gmail.com>
