perf(core): patch dotenv-expand to improve performance

[chenjiahan]

Summary

This PR patches dotenv-expand@13.0.0 with pnpm patch to avoid cloning the full processEnv object for every .env key during expansion.

The patch keeps the same expansion behavior by resolving values lazily with processEnv taking priority over runningParsed, while preserving the existing dependency path instead of forking the package inside Rsbuild.

Comparing upstream dotenv-expand@13.0.0 with the patched package using a large-project-like setup: 2,000 processEnv keys and 200 parsed .env keys.

Version	Avg	Min	Max
Upstream	51.282 ms	49.540 ms	55.521 ms
Patched	0.100 ms	0.060 ms	0.271 ms

Average speedup: ~513x.

Related

• perf: avoid cloning env during expansion dotenvx/dotenv-expand#149

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR patches dotenv-expand@13.0.0 to replace the spread-based { ...runningParsed, ...processEnv } construction inside expandValue() with a lazy getEnvValue() helper. This helper checks whether a key is an enumerable own property of processEnv before falling back to runningParsed, avoiding a full object clone on every expansion. The patch is registered in pnpm-workspace.yaml. A new e2e test case is added under e2e/cases/javascript-api/load-env-expand with .env, .env.production, and src/index.js fixture files, plus an index.test.ts that validates loadEnv correctly expands PUBLIC_* variables when a custom processEnv is supplied and that cleanup() removes the composed variable.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.
Title check	✅ Passed	The title accurately describes the main change: patching dotenv-expand to improve performance, which is the core objective of the pull request.
Description check	✅ Passed	The pull request description clearly explains the performance optimization for dotenv-expand, including benchmarks and the rationale for using pnpm patch.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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