fix(router-core): preserve encoded slashes in splat params

[xianjianlf2]

Fixes #7871.

Splat params span multiple path segments, so decoding the whole splat with decodeURIComponent makes an encoded slash inside a segment indistinguishable from a real path separator.

This decodes splat params segment-by-segment and keeps %2F encoded inside each segment. Other encoded characters in the segment, like %20, %23, and %3D, are still decoded as before. The same helper is used for fuzzy ** params.

Tests:

• pnpm --dir packages/router-core test:unit --run tests/path.test.ts
• pnpm --dir packages/router-core test:eslint
• pnpm --dir packages/history build && pnpm --dir packages/router-core test:types:ts70

Summary by CodeRabbit

• Bug Fixes
  • Fixed wildcard (*) and fuzzy catch-all (**) route parameter decoding so encoded slashes (%2F) stay within the same matched segment.
  • Improved handling of reserved characters inside wildcard and fuzzy catch-all matches.
  • Ensured encoded slashes are not treated the same as real path separators (/).
• Tests
  • Extended route matching tests to cover encoded-slash preservation and fuzzy catch-all behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: beea553e-a80c-4b46-bc17-32b30c2357f8

📥 Commits

Reviewing files that changed from the base of the PR and between cb9af0b and eda57d8.

📒 Files selected for processing (1)

• packages/router-core/src/new-process-route-tree.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/router-core/src/new-process-route-tree.ts

---

📝 Walkthrough

Walkthrough

Splat parameter decoding preserves encoded slashes within segments while decoding other characters. Wildcard and fuzzy catch-all extraction use the new behavior, with tests covering both matching modes.

Changes

Splat parameter decoding

Layer / File(s)	Summary
Segment-preserving splat decoding packages/router-core/src/new-process-route-tree.ts	Adds segment-wise splat decoding and applies it to wildcard (*) and fuzzy catch-all (**) parameters.
Splat decoding coverage packages/router-core/tests/path.test.ts	Tests encoded slashes, real separators, reserved characters, and fuzzy catch-all decoding.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% 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 clearly and concisely describes the main router-core change: preserving encoded slashes in splat params.
Linked Issues check	✅ Passed	The code and tests directly address issue #7871 by preserving encoded slashes within splat and fuzzy catch-all params.
Out of Scope Changes check	✅ Passed	The changes stay focused on splat decoding behavior and matching tests, with no unrelated scope introduced.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[xianjianlf2]

Added a short docstring for the splat decoding helper to clarify why decoding happens segment-by-segment and why encoded slashes stay escaped.

Local check:

• pnpm --dir packages/router-core test:unit --run tests/path.test.ts