Add Rspack optional peer dependency for @tailwindcss/webpack by chenjiahan · Pull Request #20027 · tailwindlabs/tailwindcss

chenjiahan · 2026-05-08T14:07:55Z

Summary

This PR makes Rspack support explicit for @tailwindcss/webpack by adding @rspack/core as an optional peer dependency alongside webpack.

The loader already works through Rspack's webpack-compatible loader API, as shown in this runnable example: https://github.com/rstackjs/rstack-examples/tree/main/rspack/tailwindcss. The README and package description are updated to document that usage.

Test plan

No Rspack-specific tests were added. The loader implementation is unchanged, and the existing webpack loader tests exercise the same loader API path that Rspack uses, which should cover the relevant behavior.

greptile-apps · 2026-05-08T14:10:26Z

Confidence Score: 5/5

Safe to merge — only package metadata and changelog are touched; the loader implementation is completely unchanged.

The diff is limited to adding an optional peer dependency entry and a changelog line. No runtime code paths are affected, and the existing webpack tests continue to cover the loader API that Rspack uses.

No files require special attention.

_{Reviews (8): Last reviewed commit: "update changelog" | Re-trigger Greptile}

coderabbitai · 2026-05-08T14:10:49Z

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CHANGELOG.md

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CHANGELOG.md

Walkthrough

The @tailwindcss/webpack package.json is updated to support both webpack and Rspack as optional peer dependencies. The webpack peer dependency is updated from ^5 to ^5.0.0, and a new @rspack/core peer dependency (^1.0.0 || ^2.0.0) is added. A peerDependenciesMeta section marks both dependencies as optional, allowing the package to work with either bundler independently. A CHANGELOG entry was added under Unreleased → Fixed noting the Rspack installation fix.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding Rspack as an optional peer dependency for the `@tailwindcss/webpack` package.
Description check	✅ Passed	The description provides relevant context about the PR, explaining why Rspack support is being added, referencing an existing runnable example, and detailing the testing approach.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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coderabbitai

Actionable comments posted: 2

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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@packages/`@tailwindcss-webpack/package.json:
- Around line 47-53: The package marks both "webpack" and "@rspack/core" as
optional peer dependencies in packages/@tailwindcss-webpack/package.json, so add
a clear note to the README installation section for the `@tailwindcss/webpack`
package that users must install at least one bundler (either webpack or
`@rspack/core`) before using the loader; update the installation/usage docs
(README) to state this requirement, show example install commands for both
options (npm/yarn/pnpm), and warn that omitting both will cause a runtime error
when the loader (the `@tailwindcss/webpack` package) is invoked.

In `@packages/`@tailwindcss-webpack/README.md:
- Around line 73-88: The example in rspack.config.js uses ESM import/export
(import { rspack } from '@rspack/core'; export default { ... }) which will throw
for projects without "type": "module"; fix by changing the snippet to a CommonJS
form (use require('...') and module.exports = ...) or instruct readers to rename
the file to rspack.config.mjs or add "type": "module" in package.json; update
the README around the rspack and CssExtractRspackPlugin example to present one
of these safe alternatives and mention the requirement for ESM if keeping
import/export.

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packages/@tailwindcss-webpack/README.md
packages/@tailwindcss-webpack/package.json

Copilot

Pull request overview

This PR makes Rspack support explicit for @tailwindcss/webpack by documenting Rspack usage and adding @rspack/core as an optional peer dependency so Rspack projects don’t see incorrect peer warnings.

Changes:

Update @tailwindcss/webpack README and package description to mention Rspack support and provide a Rspack config example.
Add @rspack/core as an optional peer dependency for @tailwindcss/webpack (and mark peers as optional via peerDependenciesMeta).
Update pnpm-lock.yaml to include @rspack/core and its resolved dependencies.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 4 comments.

File	Description
pnpm-lock.yaml	Adds lock entries for `@rspack/core` and associated packages as part of making Rspack support explicit.
packages/@tailwindcss-webpack/README.md	Documents Rspack usage alongside webpack and updates the short package description text.
packages/@tailwindcss-webpack/package.json	Updates package description and declares `@rspack/core` (and webpack) in peer dependency metadata.

Files not reviewed (1)

pnpm-lock.yaml: Language not supported

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chenjiahan · 2026-05-20T05:35:41Z

@RobinMalfait Could you take a look? ❤️

RobinMalfait · 2026-05-21T12:36:40Z

Hey! I appreciate the PR, but I'm having a hard time figuring out what the actual benefit is given that @tailwindcss/webpack already works in an Rspack project?

This might allow you to not install webpack at all, but since css-loader is also required and depends on webpack you will get webpack anyway during the installation process.

There are a few webpack drop-in replacements today, and adding all of them as optional peer dependencies seems a bit too much. Especially in a time where supply chain attacks happen left and right, I think it's better to reduce the amount of dependencies, especially since it already works as-is today.

Going to close this for now, we can revisit this if this causes any issues.
Thanks again for the PR!

chenjiahan · 2026-05-21T14:03:08Z

Thanks for taking a look!

One thing I wanted to mention is that making both webpack and @rspack/core optional peer dependencies is a common pattern across many webpack/Rspack loaders, including the ones maintained by the webpack team:

css-loader: https://github.com/webpack/css-loader/blob/main/package.json#L45-L56
postcss-loader: https://github.com/webpack/postcss-loader/blob/main/package.json#L91-L103
sass-loader: https://github.com/webpack/sass-loader/blob/main/package.json#L93-L112
less-loader: https://github.com/webpack/less-loader/blob/main/package.json#L90-L102

For projects using Rspack, it would be nice if users didn’t need to install webpack just to satisfy the peer dependency, since that would add an extra dependency that isn’t actually used.

Rspack has also become a fairly widely used webpack-compatible bundler, with @rspack/core now seeing over 6M weekly downloads on npm: https://www.npmjs.com/package/@rspack/core

So my thought was that @tailwindcss/webpack could follow the same pattern as those loaders and make the integration work a bit more smoothly for Rspack users.

chenjiahan · 2026-05-23T03:45:59Z

@RobinMalfait Would you be open to reopening this PR and continuing the discussion? We’d be happy to adjust the approach in any way that makes this more acceptable.

It's still considered a webpack plugin, but this PR makes it better compatible with Rspack as well, similar to existing loaders in the ecosystem: - https://github.com/webpack/css-loader/blob/main/package.json#L45-L56 - https://github.com/webpack/postcss-loader/blob/main/package.json#L91-L103 - https://github.com/webpack/sass-loader/blob/main/package.json#L93-L112 - https://github.com/webpack/less-loader/blob/main/package.json#L90-L102

RobinMalfait · 2026-05-23T09:14:31Z

Alright you convinced me, I've re-opened the PR to update the peer dependencies. I did clean up some of the readme to keep it simple since it's still mainly considered a webpack plugin. People using Rspack will know how to translate this config.

Thanks for the PR!

chenjiahan · 2026-05-23T13:50:22Z

Thanks a lot! This will be very helpful for Rspack users.

Copilot AI review requested due to automatic review settings May 8, 2026 14:07

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chenjiahan mentioned this pull request May 17, 2026

[Feature]: @tailwindcss/webpack support web-infra-dev/rsbuild#7660

Closed

RobinMalfait closed this May 21, 2026

RobinMalfait reopened this May 23, 2026

chenjiahan and others added 3 commits May 23, 2026 11:01

Add Rspack optional peer dependency for @tailwindcss/webpack

c4dcbf9

fix: apply review feedback

bcd8315

RobinMalfait force-pushed the add_rspack_peer branch from 6da0f29 to e6743d4 Compare May 23, 2026 09:06

update changelog

450ba0a

RobinMalfait enabled auto-merge (squash) May 23, 2026 09:14

RobinMalfait approved these changes May 23, 2026

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RobinMalfait merged commit 982e920 into tailwindlabs:main May 23, 2026
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chenjiahan deleted the add_rspack_peer branch May 23, 2026 13:50

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chenjiahan commented May 8, 2026

Summary

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Confidence Score: 5/5

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