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Enable URL rewriting for PostCSS - #16965
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Co-authored-by: Jordan Pittman <jordan@cryptica.me>
Co-authored-by: Jordan Pittman <jordan@cryptica.me>
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…` in optimized builds (#20576) ## Summary Fixes #20570 Vite adds its own `postcss-import` before the PostCSS plugins of the user. Thus, when `@tailwindcss/postcss` runs, the `@import`-ed stylesheets are already inlined. Their relative `url(…)`s are still relative to their own file. At the end, Vite resolves each `url(…)` against the `source.input.file` of its declaration. Without optimization, we keep the `source` of each node (since #17775), so this works. With optimization, we parse the output of Lightning CSS again, and every node gets the input file as its `source`. `optimize` is on by default when `NODE_ENV` is `production`, and `vite build` sets it. Vite then looks for the asset next to the input file, does not find it, and keeps the URL as it is: ``` ./fonts/ExampleSans.woff2 referenced in ./fonts/ExampleSans.woff2 didn't resolve at build time, it will remain unchanged to be resolved at runtime ``` This is the problem that #16636 and #16700 reported. #16965 fixed URL rewriting only for the stylesheets that we inline ourselves. `transformAssetUrls` (#18321) has no effect here. ## Solution When we optimize, we now rewrite the relative `url(…)`s of declarations that come from another file, so that they are relative to the input file. This is the same rewrite that we do for the stylesheets that we inline ourselves. After the rewrite, the URLs match the `source` that the optimized nodes get. - We rewrite the AST that we get from PostCSS, before we compile it. The stylesheets that we load ourselves are not in that AST yet, so we do not rewrite their URLs two times. - Without optimization, nothing changes, because the nodes keep their `source`. - `transformAssetUrls: false` disables the rewrite. To share the code, `rewriteUrls` in `@tailwindcss/node` now uses a new `rewriteUrlsInAst` function. A callback gives it the base folder of each declaration. This also changes optimized builds of other setups that run `postcss-import` before `@tailwindcss/postcss`, like `postcss-cli`. Their URLs are now relative to the input file, like the URLs of the stylesheets that we inline ourselves. ## Test plan - Added unit tests in `packages/@tailwindcss-postcss/src/index.test.ts`. They run `postcss-import` before the plugin with `optimize` on, with `optimize` off, and with `transformAssetUrls: false`. The test with `optimize` on fails on `main`. - Added an integration test in `integrations/postcss/url-rewriting.test.ts`. It runs `vite build` with `@tailwindcss/postcss` in a PostCSS config. Without this change, Vite emits no fonts and the test fails. With this change, it passes. - `pnpm vitest run`: 5598 passed. - `pnpm vitest --root=./integrations run` on `postcss/url-rewriting`, `vite/url-rewriting`, `postcss/index`, `postcss/source`, `postcss/plugins`, `postcss/config`, `postcss/core-as-postcss-plugin` and `postcss/multi-root`: all passed. I did not run `postcss/next.test.ts`. - Built a Vite 8.2.0 project with a font CSS file in a package and one in a local folder. With `optimize: true`, the fonts are now emitted to `dist/assets` and the URLs are rewritten, the same as with `optimize: false`.
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Fixes #16636
This PR enables URL rebasing for PostCSS. Furthermore it fixes an issue where transitive imports rebased against the importer CSS file instead of the input CSS file. While fixing this we noticed that this is also broken in Vite right now and that our integration test swallowed that when testing because it did not import any Tailwind CSS code and thus was not considered a Tailwind file.
Test plan
Added regression integration tests
Also validated it against the repro of @tailwindcss/postcss #16962: