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fix(css): remove ?used hack (fixes #6421, #8245) #8278

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merged 2 commits into from
May 22, 2022

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@sapphi-red sapphi-red commented May 22, 2022

Description

This ?used hack was introduced by 3e3c203.

At that time, esbuild v0.12.25 was used. This version of esbuild had trouble with tree-shaking.
This is the reproduction with esbuild repl. You can see linked variable and imported variable exists in the output.

But now Vite uses esbuild v0.14.38 and tree-shake works. This is the reproduction with esbuild repl. You can see linked is removed from output. imported is still included because of new URL('---', import.meta.url).href.
So here it needs to be marked as pure.
esbuild 0.13.0+ supports /* #__PURE__ */ and it worked if I marked by using it (esbuild repl).
The same code worked successfully with terser too.

This PR removes the ?used hack and changes the css default export to export default /* #__PURE__ */ (() => ${JSON.stringify(content)})() which I showed above.
I also tested with this project (stackblitz).

commit index.js size tree-shake notes
67743a3 872B the parent commit of this PR
a49bd36 13984B because I removed ?used hack
197253e 872B because I added pure comment

fixes #6421
fixes #8245

Additional context


What is the purpose of this pull request?

  • Bug fix
  • New Feature
  • Documentation update
  • Other

Before submitting the PR, please make sure you do the following

  • Read the Contributing Guidelines.
  • Read the Pull Request Guidelines and follow the Commit Convention.
  • Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
  • Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
  • Ideally, include relevant tests that fail without this PR but pass with it.

@sapphi-red sapphi-red added feat: css p3-minor-bug An edge case that only affects very specific usage (priority) labels May 22, 2022
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This is too awesome 🔥

@patak-dev patak-dev merged commit 0b25cc1 into vitejs:main May 22, 2022
@sapphi-red sapphi-red deleted the fix/remove-css-used-query branch May 23, 2022 00:07
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sapphi-red commented May 23, 2022

This PR makes the output of import content from 'foo.css' to

const content = (() => "body{color:red}")()
console.log(content)

.

But this might hurt runtime perf if import content from 'foo.css' is used many places. https://v8.dev/blog/preparser#pife

const content = (function () { return "body{color:red}"})()
console.log(content)

This might be better for perf though the code is longer.

I'm not making a PR for this as I didn't measure the perf and it is an edge case but still leaving a note here.

sapphi-red added a commit to sapphi-red/vite that referenced this pull request Jun 5, 2022
This was referenced Jun 30, 2022
sapphi-red added a commit to sapphi-red/vite that referenced this pull request Jul 3, 2022
This reverts commit 0b25cc1.
@sapphi-red sapphi-red mentioned this pull request Jul 3, 2022
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patak-dev pushed a commit that referenced this pull request Jul 3, 2022
This reverts commit 0b25cc1.
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CSS Modules not included with import statment and resolve alias CSS is missed in transform hook
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