fix: guard missing React version export

[nrps9909]

Summary

• avoid crashing while loading rc-util/es/ref when a bundler's React interop object does not expose version
• preserve the existing React 19 check when version is available
• add a regression test for the missing-export shape

Why

rc-util@5.44.4 started reading version.split(...) at module scope, and the same unguarded read remains in the current @rc-component/util source. In the Vite production-build cases reported in #647 and #783, the React named export can be undefined, so importing ref.js throws before the application renders. Treating a missing version as an unknown version keeps the React 18-compatible path and prevents the module-load failure. A legacy rc-util release would require a maintainer backport to 5.x.

Verification

• Regression before the fix: Cannot read properties of undefined (reading 'split') at src/ref.ts
• npm test -- --runInBand — 30 suites passed, 183 tests passed, 1 skipped
• npm run tsc
• npm run compile — ESM, CommonJS, and declarations built successfully
• npx prettier --check src/ref.ts tests/ref-version.test.ts
• focused ESLint — no errors

Closes #647 and #783.

AI assistance disclosure: Codex was used to trace the regression, construct the failing interop test, and draft the patch and PR description. The failure was reproduced against the unguarded source, and all listed verification was run locally on current master.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: da1677a1-1d37-49d5-9dfa-f5742312c915

📥 Commits

Reviewing files that changed from the base of the PR and between d1045f4 and a42c5a7.

📒 Files selected for processing (2)

• src/ref.ts
• tests/ref-version.test.ts

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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Walkthrough

本次变更为 ReactMajorVersion 增加可选链访问，并新增测试。version 为 undefined 时，模块加载不再因调用 split 抛出异常。

Changes

React version 缺失处理

Layer / File(s)	Summary
version 防护与加载测试 src/ref.ts, tests/ref-version.test.ts	ReactMajorVersion 使用 version?.split('.')[0]。新增 Jest 测试，验证 React 未导出 version 时加载 src/ref 不会抛出异常。

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to a42c5

The change prevents an import-time crash when React lacks a version export while preserving the existing behavior when the version is available. No actionable merge-blocking risk remains after normal checks and review.

Poem

小兔守着 version 门，
缺失时也不惊慌。
可选链轻轻探路，
ref 模块安稳加载。
测试敲响绿色铃，
代码继续向前跑。

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	变更满足问题 #647 的主要目标。代码在 React 版本导出为 undefined 时避免调用 split，并新增回归测试验证模块加载不会抛出异常。
Out of Scope Changes check	✅ Passed	所有变更均围绕问题 #647，包括 React 版本检测修复和对应回归测试。未发现无关或超出范围的代码变更。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	标题准确概括了主要变更：为缺失的 React version 导出增加保护，避免模块加载失败。表述简洁且与 PR 目标一致。

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2 files.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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