revert: remove faster module concatenation

[LingyuCoder]

Summary

• Revert perf: avoid parsing concatenated module codegen #14852 and fix: preserve reexport call context in concatenation #15247 because the measured end-to-end benefit does not justify the added maintenance and correctness complexity.
• Restore the legacy parse-based concatenated-module code generation path.
• Preserve the module code generation cache integration added after those PRs, including ESM library concatenation scope output.

Related links

• Reverts perf: avoid parsing concatenated module codegen #14852.
• Reverts fix: preserve reexport call context in concatenation #15247.

Validation

• pnpm run build:binding:dev
• pnpm run build:js
• pnpm run test:unit
• cargo clippy --workspace --all-targets --tests --locked -- -D warnings
• cargo fmt --all -- --check
• pnpm exec rs fmt --check

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[cloudflare-workers-and-pages]

Deploying rspack with    Cloudflare Pages

Latest commit:	e87a341
Status:	✅  Deploy successful!
Preview URL:	https://ce580f3f.rspack-v2.pages.dev
Branch Preview URL:	https://seal-revert-faster-module-co.rspack-v2.pages.dev

View logs

[github-actions]

📦 Binary Size-limit

Comparing 92101da to fix: refine binding code generation result error handling (#15253) by AsyncIter

🎉 Size decreased by 220.13KB from 68.26MB to 68.05MB (⬇️0.31%)

[github-actions]

Rsdoctor Bundle Diff Analysis

⚠️ Note: The latest commit (78186afa38) does not have baseline artifacts. Using commit 91384b1a7c for baseline comparison instead. If this seems incorrect, please wait a few minutes and try rerunning the workflow.

Found 5 projects in monorepo, 0 projects with changes.

📊 Quick Summary

Project	Total Size	Gzip Size	Change	Gzip Change
popular-libs	1.7 MB	556.5 KB	0	0
react-10k	5.6 MB	1.3 MB	0	0
react-1k	823.1 KB	218.4 KB	0	0
react-5k	2.7 MB	669.3 KB	0	0
ui-components	4.9 MB	1.4 MB	0	0

Generated by Rsdoctor GitHub Action

[codspeed]

Merging this PR will degrade performance by 19.11%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 3 regressed benchmarks
✅ 47 untouched benchmarks
⏩ 47 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	rust@concatenate_module_code_generation	32.5 ms	44.4 ms	-26.72%
❌	Simulation	bundle@threejs-production-sourcemap	148.6 ms	191.8 ms	-22.52%
❌	Simulation	bundle@misc-production-sourcemap	3.3 s	3.6 s	-6.77%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing seal/revert-faster-module-concatenation (92101da) with main (91384b1)}

Footnotes

1. 47 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

📝 Rspack Ecosystem CI: Open

suite	result
rsbuild	✅ success
examples	❌ failure
rsdoctor	✅ success
modernjs	❌ failure
lynx-stack	❌ failure
rstest	❌ failure
rspress	✅ success
devserver	✅ success
plugin	✅ success
rsbuild-rsc-plugin	✅ success
rslib	✅ success