fix(react-router): avoid Webpack inlining React.use static analysis

[SAY-5]

Per #7176, recent bundler updates inline const REACT_USE = 'use'; React[REACT_USE] back into the literal React['use'] in the published package, which re-triggers Webpack's static analysis and breaks builds against React 18 (which doesn't export use).

This was previously fixed by #6355, but the bundled output regressed somewhere between #6355 and #6926.

This PR replaces the manual indirection with Reflect.get(React, 'use'). Reflect.get is a real runtime call — bundlers don't fold it into a direct property access — so the property name never appears as a static literal in the bundled output, and Webpack's static analyzer has nothing to flag.

Closes #7176

Summary by CodeRabbit

• Refactor
  • Internal runtime lookup logic adjusted to be safer and more defensive; preserves existing behavior while improving robustness and maintainability, with no changes to public APIs or user-facing functionality.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a4a352d8-2edd-4599-8fd3-53ea3c3a2095

📥 Commits

Reviewing files that changed from the base of the PR and between 9396596 and 80a7859.

📒 Files selected for processing (1)

• packages/react-router/src/utils.ts

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📝 Walkthrough

Walkthrough

Replaces module-level string constant and bracket-style lookup for React's "use" with a runtime Reflect.get(React, 'use') lookup and assigns reactUse only if the retrieved value is a function; no exported signatures were changed.

Changes

Cohort / File(s)	Summary
React.use access change packages/react-router/src/utils.ts	Removed REACT_USE constant and replaced (React as any)[REACT_USE] with Reflect.get(React, 'use'). reactUse now conditionally assigns only when the retrieved candidate is a function; export type and signature unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I peeked at React and gave a small tug,
Swapped a string for Reflect — light as a hug,
Only a function earns my nod and cheer,
Webpack blinks, the build runs clear! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: using Reflect.get to avoid Webpack static analysis of the React.use property access.
Linked Issues check	✅ Passed	The PR directly addresses issue #7176 by replacing direct property access with Reflect.get(React, 'use') to prevent Webpack's static analysis from detecting the 'use' property name, resolving the build error with React 18.
Out of Scope Changes check	✅ Passed	All changes in utils.ts are scoped to fixing the Webpack regression for React.use property access; no unrelated modifications detected.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

Bundle Size Benchmarks

• Commit: 0166fe8ba0f3
• Measured at: 2026-04-15T04:49:05.336Z
• Baseline source: history:f7f00250f39c
• Dashboard: bundle-size history

Scenario	Current (gzip)	Delta vs baseline	Raw	Brotli	Trend
react-router.minimal	87.37 KiB	+28 B (+0.03%)	274.65 KiB	75.88 KiB	▂▁▁▁▁▁▁▃▃▃▃█
react-router.full	90.66 KiB	+28 B (+0.03%)	285.79 KiB	78.79 KiB	▃▁▁▁▁▁▁▂▂▅▅█
solid-router.minimal	35.51 KiB	0 B (0.00%)	106.60 KiB	31.91 KiB	█▁▁▁▁▁▁▃▃▃▃
solid-router.full	39.99 KiB	0 B (0.00%)	120.09 KiB	35.93 KiB	█▁▁▁▁▁▁▆▆▆▆
vue-router.minimal	53.30 KiB	0 B (0.00%)	152.01 KiB	47.88 KiB	█▁▁▁▁▁▁▄▄▄▄
vue-router.full	58.20 KiB	0 B (0.00%)	167.43 KiB	52.06 KiB	█▁▁▁▁▁▁▄▄▄▄
react-start.minimal	101.79 KiB	+21 B (+0.02%)	322.44 KiB	88.06 KiB	▃▁▁▁▁▁▁▂▂▅▅█
react-start.full	105.23 KiB	+24 B (+0.02%)	332.77 KiB	90.88 KiB	▃▁▁▁▁▁▁▂▂▅▅█
solid-start.minimal	49.52 KiB	0 B (0.00%)	152.41 KiB	43.66 KiB	█▁▁▁▁▁▁▄▄▄▄
solid-start.full	55.04 KiB	0 B (0.00%)	168.61 KiB	48.44 KiB	█▁▁▁▁▁▁▅▅▅▅

Trend sparkline is historical gzip bytes ending with this PR measurement; lower is better.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@packages/react-router/src/utils.ts`:
- Around line 17-19: The exported reactUse is assigned via Reflect.get(React,
'use') which is typed as any at runtime; add a runtime guard that verifies the
retrieved value is actually a function (and optionally has arity 1) before
assigning/exporting it so the runtime value matches the declared signature.
Replace the direct Reflect.get usage with a checked assignment: get the
candidate via Reflect.get(React, 'use'), verify typeof candidate === 'function'
(and candidate.length === 1 if you want stricter validation), and only then cast
and export it as reactUse; otherwise export undefined. This uses the existing
reactUse symbol and Reflect.get(React, 'use') location to find and fix the code.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 10224a06-e4b6-4a96-8b78-cc7cad4debf5

📥 Commits

Reviewing files that changed from the base of the PR and between 0166fe8 and 9396596.

📒 Files selected for processing (1)

• packages/react-router/src/utils.ts