Raise actionable error for components declaring library react-router-dom

[masenf]

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• Have you followed the guidelines stated in CONTRIBUTING.md file?
• Have you checked to ensure there aren't any other open Pull Requests for the desired changed?

Type of change

• Bug fix (non-breaking change which fixes an issue)

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Defect

FINDING-010 (MEDIUM) from the 0.9.9a1 pre-release testing round: React Router 8 dropped the react-router-dom re-export package and Reflex no longer installs it (#6854), but a custom component declaring library = "react-router-dom" still fell through the generic custom-library install path. bun add then installed an unpinned react-router-dom@^7, nesting a second React Router 7 copy beside the first-party v8:

• Dev: the component rendered and navigated with no warning (vite dedupes to the hoisted v8 copy), and the stray dependency was persisted into reflex.lock/package.json — working purely by accident.
• Prod: the build failed at prerender with the cryptic TypeError: Cannot destructure property 'basename' of React10.useContext(...) as it is null, exit 1, with nothing pointing at the real cause.

Fix

Component._get_imports (reflex-base) now checks the component's merged import contributions — library, lib_dependencies, and add_imports alike — and raises a pointered ValueError when any of them resolves to the removed react-router-dom package. The bare name, versioned forms (react-router-dom@7.18.2), and subpath imports (react-router-dom/server, react-router-dom@7.18.2/server) are all caught; similarly named but distinct packages (e.g. react-router-dom-fork) are not. The error names the offending component and tells the author to use library = "react-router" (or "react-router/dom" for RouterProvider/HydratedRouter), matching the migration documented in the React Router 8 changelog entry:

ValueError: The component `BadDomLink` references `react-router-dom`, but React Router 8 removed the `react-router-dom` package and Reflex no longer installs it. Use `library = "react-router"` instead, or `"react-router/dom"` for `RouterProvider`/`HydratedRouter`.

The check sits in the per-component import-collection chokepoint (before the imports cache is populated), so it fires at compile/collection time in both dev and prod, names the component that declared the library, and costs a single startswith pre-filter per import key. News fragments added under news/ and packages/reflex-base/news/.

Test plan

• New regression tests in tests/units/components/test_component.py:
  • test_get_imports_rejects_react_router_dom_library (parametrized over the bare, versioned, subpath, and versioned+subpath forms) — all 4 fail with DID NOT RAISE ValueError on unfixed main, pass with the fix.
  • test_get_imports_rejects_react_router_dom_lib_dependency — fails on unfixed main, passes with the fix.
  • test_get_imports_allows_react_router_libraries — react-router, react-router/dom, and react-router-dom-fork remain accepted.
• uv run pytest tests/units/components tests/units/compiler — 4338 passed; uv run pytest tests/units/test_app.py tests/units/reflex_base — 393 passed.
• uv run ruff check . and uv run ruff format . clean; uv run pyright reflex tests packages/reflex-base — 0 errors (one pre-existing warning in an untouched file).
• uv run python scripts/make_pyi.py — no pyi_hashes.json changes.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EMjBXPozsNeQNSBZecNH8x

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Generated by Claude Code

[greptile-apps]

Greptile Summary

The PR adds compile-time validation that rejects component import contributions resolving to the removed react-router-dom package.

• Checks merged imports before caching them.
• Handles bare, versioned, and subpath package forms while allowing similarly named packages.
• Adds focused regression tests and a bug-fix news fragment.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/components/component.py	Adds a centralized prohibited-import guard and invokes it on each component’s merged import contributions before caching.
tests/units/components/test_component.py	Covers rejected bare, versioned, subpath, and dependency forms, plus accepted replacement and similarly named libraries.
packages/reflex-base/news/+react-router-dom-guard.bugfix.md	Documents the new actionable compilation failure and supported React Router replacements.

_{Reviews (3): Last reviewed commit: "Delete news/+react-router-dom-guard.bugf..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 32 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing claude/rel-fix-react-router-dom-guard (b56951a) with main (34bdfc3)}

Footnotes

1. 8 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. ↩

[cubic-dev-ai]

All reported issues were addressed across 4 files

<sub>Reply with feedback, questions, or to request a fix.

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