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fix(react-router): prevent incorrectly matching paths without slash separator#14689

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brophdawg11 merged 5 commits intoremix-run:devfrom
nwleedev:feature/match-path-regex-pattern-fix
Jan 21, 2026
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fix(react-router): prevent incorrectly matching paths without slash separator#14689
brophdawg11 merged 5 commits intoremix-run:devfrom
nwleedev:feature/match-path-regex-pattern-fix

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@nwleedev
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@nwleedev nwleedev commented Dec 27, 2025

Problem

Optional dynamic segments (:param?) incorrectly match paths that extend the base path without a separator. For example:

matchPath('/test_route/:part?', '/test_route_more')
// Expected: null
// Actual: { params: { part: '_more' } }

The current regex pattern /?([^\/]+)? makes the slash and capture group independently optional.
It allows /test_route_more to match as /test_route + _more without a preceding slash.

Changes

The regex pattern to match paths

  • Groups the slash with the capture
  • Ensures slash and parameter appear together or not at all
  • Uses * instead of + to allow empty captures for backward compatibility
    (e.g., /sitemap/:lang?.xml matching /sitemap/.xml)

Impact

  • No breaking changes
    • Only fixes incorrect matching behavior
  • Maintains backward compatibility with existing patterns

Fixes #14640

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changeset-bot Bot commented Dec 27, 2025 •
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🦋 Changeset detected

Latest commit: e3c81b0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages
Name Type
react-router Patch
@react-router/architect Patch
@react-router/cloudflare Patch
@react-router/dev Patch
react-router-dom Patch
@react-router/express Patch
@react-router/node Patch
@react-router/serve Patch
@react-router/fs-routes Patch
@react-router/remix-routes-option-adapter Patch
create-react-router Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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remix-cla-bot Bot commented Dec 27, 2025

Hi @nwleedev,

Welcome, and thank you for contributing to React Router!

Before we consider your pull request, we ask that you sign our Contributor License Agreement (CLA). We require this only once.

You may review the CLA and sign it by adding your name to contributors.yml.

Once the CLA is signed, the CLA Signed label will be added to the pull request.

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- The Remix team

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remix-cla-bot Bot commented Dec 27, 2025

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

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brophdawg11 commented Jan 5, 2026

Would you mind adding a changeset via pnpm changeset?

@nwleedev
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nwleedev commented Jan 5, 2026

Would you mind adding a changeset via pnpm changeset?

Apologies for missing the changeset request. I have created a patch changeset for react-router.

brophdawg11
brophdawg11 reviewed Jan 12, 2026
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Comment thread packages/react-router/lib/router/utils.ts Outdated
(_: string, paramName: string, isOptional) => {
params.push({ paramName, isOptional: isOptional != null });
return isOptional ? "/?([^\\/]+)?" : "/([^\\/]+)";
return isOptional ? "(?:/([^\\/]*))?" : "/([^\\/]+)";
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@brophdawg11 brophdawg11 Jan 12, 2026

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Making the question mark optional can cause issues when there is a suffix after the param - here's a failing case:

expect(matchPath("/sitemap/:lang?.xml", "/sitemap.xml")?.params).toBeNull();

Normally we do require the params to be the full segment, but the dot notation slipped through out original implementations and enough apps rely on it that it would be a breaking change at this point so we plan to continue supporting it.

Can you see if there's a different solution that plays nicely with that format?

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nwleedev commented Jan 15, 2026

Checked the suffix case you mentioned and adjusted the approach to preserve dot-notation compatibility.

  • Added a regression test to ensure matchPath("/sitemap/:lang?.xml", "/sitemap.xml") returns null.
  • Kept existing dot-notation behavior working.
    • "/sitemap/en.xml" matches with { lang: "en" }
    • "/sitemap/.xml" matches with { lang: undefined }
  • Updated compilePath so optional params without a suffix require the slash+param to appear together.
    • Prevented cases like /test_route_more matching /test_route/:part?.
    • For optional params with a same-segment suffix, the segment is not made fully optional.

@brophdawg11 brophdawg11 self-requested a review January 16, 2026 14:36
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brophdawg11 commented Jan 21, 2026

Thanks!

@brophdawg11 brophdawg11 merged commit 7535805 into remix-run:dev Jan 21, 2026
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@github-actions github-actions Bot mentioned this pull request Feb 18, 2026
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github-actions Bot commented Feb 18, 2026

🤖 Hello there,

We just published version 7.13.1-pre.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

@github-actions github-actions Bot mentioned this pull request Feb 23, 2026
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github-actions Bot commented Feb 23, 2026

🤖 Hello there,

We just published version 7.13.1 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

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