Walkthrough

Adds a new Pro documentation page describing experimental Rspack compatibility for React on Rails Pro’s React Server Components and extends generator specs with assertions that Rspack-specific RSC config files, bundle naming, loader-chain handling, plugin conditionals, and environment-variable routing are generated.

Changes

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐇 I nibbled docs and hopped through tests,
Rspack and RSC stitched into new vests,
Bundles named, configs penned with glee,
A little rabbit celebrates compatibility! 🌿🥕

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Review Summary

Overall this is a well-scoped PR — documentation-only plus generator spec additions, no runtime behaviour changed. A few things to address before merging:

Must fix

Weak alias assertion (rsc_generator_spec.rb line 682): The test titled "aliases react-dom/server to false" only checks that the string react-dom/server appears in the file, so it would pass even if the false value were removed. Change the assertion to include("'react-dom/server': false").

Unverified citation (rspack-compatibility.md line 52): The sentence "The Rspack team has confirmed … RSC with the JavaScript API" links to #issuecomment-3350629010. That comment ID couldn't be verified during this review — please confirm the URL is live and contains the stated claim. A broken citation in public docs erodes credibility.

Suggestions

• Duplicate test coverage: Several assertions in the new describe "Rspack RSC runtime compatibility" block (e.g. RSC_BUNDLE_ONLY, rscConfig, RSCWebpackPlugin) are already covered by the "RSC webpack config transforms in config/rspack/" block above. The new tests are intentionally more specific, which is fine — just worth a comment in the spec noting that so future maintainers don't collapse them.

• Misleading test description (line 704): "handles both function-based (SWC) and array-based (Babel) loader chains" — the test checks for the presence of conditional logic strings, not actual loader insertion. Consider renaming to something like "contains conditional loader-chain handling for both function-based and array-based rule.use".

Looks good

• The compatibility matrix is accurate and well-structured.
• The "WebpackPlugin Compatibility Details" section correctly identifies the risk boundary (plugin vs. loader).
• The generated template assertions are well-matched to actual template content.
• No security or performance concerns in this change set.

Greptile Summary

This PR adds a new documentation page (docs/pro/react-server-components/rspack-compatibility.md) covering the experimental Rspack + RSC status, and extends rsc_generator_spec.rb with 9 new RSpec tests inside a dedicated describe "Rspack RSC runtime compatibility" block nested under the existing context "when Pro is installed on an existing rspack project". No production code is modified. Prior review concerns (weak false-alias assertion, misleading LimitChunkCountPlugin test description) have been fully addressed in ab3fb6dc.

Confidence Score: 5/5

Safe to merge — only documentation and additional generator spec assertions are changed; no production or generator logic is modified.

All findings from prior review rounds are resolved. Both changed files are non-production: one is a markdown doc page (all relative links verified to exist), the other is a spec file adding 9 tests inside an existing generator context with a shared before(:all). No P0 or P1 issues remain.

No files require special attention.

Important Files Changed

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[RSC Generator] --> B{rspack_configured_in_project?}
    B -- Yes --> C[Write to config/rspack/]
    B -- No --> D[Write to config/webpack/]

    C --> E["rscWebpackConfig.js\nconditionNames + react-server alias\nWebpackLoader chain\nserverWebpackConfig(true)"]
    C --> F["serverWebpackConfig.js\nrscBundle param\nif(!rscBundle) RSCWebpackPlugin\nLimitChunkCountPlugin"]
    C --> G["ServerClientOrBoth.js\nRSC_BUNDLE_ONLY routing\nclientConfig + serverConfig + rscConfig"]

    E --> H[rsc-bundle.js\nNo plugin needed]
    F --> I[react-client-manifest.json\nreact-ssr-manifest.json]
    G --> J[Three-bundle build]

    F -.->|Needs Rspack v2 verification| K[RSCWebpackPlugin\nwebpack internal APIs]

_{Reviews (2): Last reviewed commit: "Address PR review feedback on RSC genera..." | Re-trigger Greptile}

Review feedback addressed in ab3fb6d

Fixed (4 items):

1. Tightened alias assertion — include("react-dom/server") → include("'react-dom/server': false") so the test actually verifies the false value (flagged by @claude[bot], @chatgpt-codex-connector[bot], @greptile-apps[bot])
2. Clarified LimitChunkCountPlugin test origin — renamed test and updated comment to note this content comes from the Pro generator, not the RSC generator (@greptile-apps[bot])
3. Renamed loader-chain test — now "contains conditional loader-chain handling for function-based and array-based rule.use" to accurately describe what it checks (@claude[bot])
4. Added duplication rationale — comment above describe block explains overlap with earlier assertions is intentional (@claude[bot])

Skipped (verified):

• Citation link #issuecomment-3350629010 — confirmed live and accurate; the Rspack team comment exists and states "Currently, Rspack already supports RSC with JavaScript API"

All 76 RSpec examples pass. All 7 review threads resolved.

— I (Claude Code)

To use Codex here, create an environment for this repo.

Follow-up review (commit ab3fb6d)

All four items from the first review are addressed:

1. Alias assertion tightened — now checks 'react-dom/server': false (line 682). ✓
2. LimitChunkCountPlugin test renamed and commented — correctly notes the content originates from the Pro generator (line 715). ✓
3. Loader-chain test renamed — description now accurately says "contains conditional loader-chain handling" rather than implying actual loader insertion (line 707). ✓
4. Duplication rationale added — the block-level comment at line 667 explains the intentional overlap. ✓

One remaining nit

The test at line 694 verifies the skip via an indirect signal (serverWebpackConfig(true)) but not the direct outcome — see inline comment. Adding not_to include("RSCWebpackPlugin") makes the intent self-documenting and catches template drift. Optional, but recommended.

Documentation

rspack-compatibility.md is accurate and well-structured. One future maintenance note: the linked Rspack RSC support PR (web-infra-dev/rspack/pull/5824) will become stale once merged — consider updating that reference to point to the Rspack changelog or stable docs page when Rspack officially ships RSC support.

No security, performance, or correctness concerns. Safe to merge as-is.

Review: #3120 — Rspack + RSC compatibility tests and documentation

Low-risk PR overall. The documentation is clear and the test additions are well-motivated. A few issues worth addressing before merge:

Critical

Unverifiable documentation claim (doc line 52) — The link #issuecomment-3350629010 should be confirmed to resolve before this lands. Comment IDs that large are unusual; if the anchor is wrong the docs make an authoritative "Rspack team has confirmed" claim with a dead link. See inline comment.

Moderate

Misleading comment in test 7 (LimitChunkCountPlugin) — The comment says "This content comes from the Pro generator" but it actually comes from the pro_server_webpack_content fixture in generator_spec_helper.rb. The test intent (regression guard: RSC generator must not remove LimitChunkCountPlugin) is valid, the comment just misrepresents the source. See inline.

Minor

• describe block name ("Rspack RSC runtime compatibility") — These are generator output assertions, not runtime tests. A name like "generated Rspack RSC config bundler-agnostic patterns" is more accurate.
• Test 5 mixes two concerns — "renames entry to rsc-bundle" checks both the entry key and the output filename; these are separate config mutations worth splitting.
• Acknowledged duplication — The overlap with the "RSC webpack config transforms" block (particularly the RSC_BUNDLE_ONLY / rscConfig checks in the ServerClientOrBoth.js test) is called out in the comment, which is good. Just flagging it in case a future reader wonders.

What looks good

• Compatibility matrix in the doc is accurate and directly traceable to the rscWebpackConfig.js.tt template content.
• All 9 new specs map to real template strings (verified by reading the template); the assertions themselves are correct.
• Sidebar placement (upgrading-existing-pro-app → rspack-compatibility → glossary) is sensible.
• The before(:all) setup is shared from the enclosing context — no duplicate fixture setup needed.

Follow-up review feedback addressed in 17708ef

Fixed (1 item):

1. Added negative assertion for RSCWebpackPlugin — the serverWebpackConfig(true) test now also verifies that RSCWebpackPlugin is not instantiated in the RSC config (not_to match(/new\s+RSCWebpackPlugin/)). Used a regex instead of the suggested not_to include("RSCWebpackPlugin") because the template legitimately contains the name in a comment explaining the skip. (@claude[bot])

Skipped (5 items):

• CodeRabbit walkthrough summary — bot status post, no action needed
• Initial review summary — all items were already addressed in ab3fb6d
• Greptile summary ("Safe to merge") — bot status post, no action needed
• Codex connector setup prompt — bot status post
• Follow-up review acknowledgment — confirmation that prior fixes were correct (nit captured in TODO for first version #1 above)

All 76 RSpec examples pass. All 8 review threads now resolved.

— I (Claude Code)