Upgrade Rspack SWC

Perform the upgrade end to end. Keep the patch focused, preserve unrelated work, and base every changelog claim on the SWC tag range.

Guardrails

Confirm the checkout is web-infra-dev/rspack and read the applicable AGENTS.md instructions before editing.
Inspect git status --short, the current branch, and remotes first. Never overwrite, discard, stage, or commit unrelated user changes. Stop for direction if unrelated changes overlap the files required by the upgrade.
Use exact, stable, non-yanked crate versions. Ignore prereleases unless the user explicitly requests one.
Treat the root Cargo.toml comment Must be pinned with the same swc versions as an invariant. Keep SWC direct dependencies on one compatible release set; do not blindly bump only swc_core.
Treat every swc_experimental_* crate as independent and out of scope. Never query, bump, or otherwise change its manifest or lockfile version as part of this workflow.
Keep existing default-features, feature lists, and unrelated dependency versions unchanged unless the new SWC release requires an adaptation.
Do not edit crates/rspack_workspace/src/generated.rs by hand. Generate it with cargo codegen.
Use official sources for release data: crates.io and swc-project/swc tags, commits, and pull requests.
Mention an upstream bug fix in the PR description only when it matches a Rspack issue's failure mode and the fix is validated when practical. Omit plausible, weak, or unverified bug connections instead of using “related” or “may fix”.
Use pnpm run build:binding:dev as the only validation command. Do not run tests or lint unless the user explicitly requests them.
Do not create the PR until the intended diff and required validation have been reviewed. If validation is incomplete or an important risk remains, explain it and open a draft only when the user still wants a PR.

1. Establish the version range

Read the SWC dependency block in the repository root Cargo.toml and record the exact current swc_core version as OLD_VERSION.
Query crates.io for the newest stable, non-yanked swc_core release and record it as NEW_VERSION. Cross-check that the tag swc_core@NEW_VERSION exists in https://github.com/swc-project/swc.
Stop with a no-op report if OLD_VERSION already equals NEW_VERSION.
Enumerate the in-scope direct root dependencies named swc or beginning with swc_. At swc_core@NEW_VERSION, inspect the SWC workspace and crate manifests to identify their release-compatible versions. Also check crates.io for compatible patch releases published after the tag.
Update only those in-scope entries in the root Cargo.toml. If the upgrade cannot resolve without changing an excluded dependency, stop and report the incompatibility instead of expanding scope.
Refresh Cargo.lock through Cargo resolution, using a precise swc_core update where needed. Inspect resolution errors rather than loosening pins or features speculatively.
Check the resolved SWC graph for unintended duplicate major versions, especially swc_common, AST, parser, transform, minifier, plugin, and HTML crates. Resolve incompatible direct pins before proceeding.

Preserve full semantic versions for Cargo and tag operations. For the PR title labels, follow the recent Rspack SWC bump convention: use major-only labels for a major-to-major bump, otherwise use the shortest unambiguous semantic versions.

2. Regenerate workspace code

Run from the repository root:

bash

cargo codegen

Verify that crates/rspack_workspace/src/generated.rs contains NEW_VERSION in rspack_swc_core_version() and that no unrelated generated values changed.

3. Build the tag-to-tag changelog

Use these exact refs:

text

swc_core@OLD_VERSION...swc_core@NEW_VERSION

Create the canonical comparison link:

text

https://github.com/swc-project/swc/compare/swc_core%40OLD_VERSION...swc_core%40NEW_VERSION

Collect the complete commit list through the GitHub compare API or the exact tag refs in a temporary/local SWC checkout. Paginate and de-duplicate by SHA. If GitHub truncates a large comparison, split it across consecutive swc_core@... tags and merge the results. Do not substitute dates, branches, or release-page prose for the tag range.

For commits that reference a pull request, inspect that PR’s title, body, labels, and relevant files. Drop release bookkeeping, dependency noise, and merges with no user-visible impact. Classify the remaining changes as:

breaking changes that require a Rspack adaptation or materially affect a Rspack integration surface;
new features available through a Rspack integration surface;
performance improvements that plausibly benefit Rspack;
bug fixes that match a verified Rspack issue.

For every included item, link the upstream PR or commit and explain the concrete Rspack surface it affects. Search the Rspack checkout for changed SWC API names and behavior so the summary reflects actual integration points instead of repeating upstream titles. Omit changes with no meaningful Rspack impact. Do not add empty categories or state that there are no relevant changes.

Search open and recent Rspack issues using the symptoms, syntax, transform names, and error text from notable SWC fixes. Read candidate issues and confirm the behavior matches from the available issue details, upstream fix, and local integration code. Do not run tests as part of this workflow. Record verified issue links for the PR.

Keep issue correlation as an analysis step, not a reporting requirement. If no Rspack issue is verified, omit the bug fix and omit the related-links section entirely. Never list upstream bug fixes solely to summarize the SWC release.

4. Adapt and validate

Fix compilation changes caused by the new SWC release with the smallest compatible patch. Validate the upgrade by running only:

bash

pnpm run build:binding:dev

Do not run unit tests, integration tests, end-to-end tests, lint, or additional validation commands unless the user explicitly requests them. If the build fails because of the SWC upgrade, make the smallest necessary compatibility fix and rerun the same build command. If an environment failure prevents the build, capture the exact failure; never present it as passing.

Review the final diff. Expected files are normally root Cargo.toml, Cargo.lock, and crates/rspack_workspace/src/generated.rs, plus only necessary compatibility changes. Confirm the generated version is correct and inspect the resolved SWC versions one final time.

5. Commit and open the PR

Use this exact title shape, retaining the backticks:

text

chore: bump `swc_core` from FROM_LABEL to TO_LABEL

Use the same subject for the commit unless repository history indicates a necessary commit-only variation. Stage only intended paths, review the staged diff, commit, push the current feature branch, and open the PR against main.

Build the PR description from .github/PULL_REQUEST_TEMPLATE.md. Keep it brief and evidence-based:

markdown

## Summary

Bumps `swc_core` from `OLD_VERSION` to `NEW_VERSION` and aligns the compatible SWC dependency pins.

[Upstream tag comparison](COMPARE_URL)

- **Breaking:** <only Rspack-impacting breaking changes or required adaptations; omit when empty>
- **Features:** <new capabilities available through Rspack; omit when empty>
- **Performance:** <improvements likely to benefit Rspack; omit when empty>
- **Fixes:** <only fixes matched to verified Rspack issues; omit when empty>

## Related links

<Include this section only when verified Rspack issue links exist. Use `Fixes #NNNN` only for confirmed fixes.>

## Checklist

- [x] Tests updated (or not required).
- [x] Documentation updated (or not required).

## Validation

- `<exact command>`

Include only useful changelog detail in the PR body; do not dump the raw commit list. Prefer omitting a low-confidence or low-impact item over making reviewers evaluate it. Remove empty optional bullets and sections from the final body. Mark a checklist item complete only when true, and state why tests or docs are not required when that is not obvious. After creation, report the PR URL, exact version range, changed files, validation results, and any remaining risks.