perf(url): avoid full parse when reading hash on the fast path

[danielroe]

context: found this profiling Nuxt's SSR path, where we build the render URL as pathname + search + hash

reading url.hash on a FastURL costs a full parse, because there's no hash getter

but ... there's nothing to find in that parse on the fast path. so in that case we can optimise by returning ''. quick measurement: 500k iterations, node 22, object-form input:

hash (object form)               316 ns -> 40 ns
hash (origin-form string)        229 ns -> 25 ns
hash (absolute string with '#')  228 ns -> 228 ns
pathname (already fast)           40 ns

Summary by CodeRabbit

• New Features

  • Added a hash property to URL handling, enabling access to URL fragments.
  • Fragment values are preserved for absolute URLs and reflected when updated.

• Bug Fixes

  • Improved fragment parsing consistency across URL formats.
  • Ensured fragment values remain consistent before and after URL processing.

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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: 72c9e57f-c619-44f2-84f6-1210c0373361

📥 Commits

Reviewing files that changed from the base of the PR and between 053be62 and 176ffcb.

📒 Files selected for processing (2)

• src/_url.ts
• test/url.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

Walkthrough

FastURL now exposes a hash getter. Fast-path URLs return an empty hash, while materialized URLs delegate to the native URL. Tests cover fragments, deoptimization, absolute-form inputs, and setter behavior.

Changes

FastURL hash support

Layer / File(s)	Summary
Add FastURL hash access src/_url.ts	The documentation lists url.hash as fast-path accessible. The getter returns an empty string on the fast path and delegates to the native URL after materialization.
Validate hash behavior test/url.test.ts	Tests compare hashes with native URL parsing and cover fast-path, absolute-form, deoptimized, and setter behavior.

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

Merge Risk: ⚪ Minimal · up to 176ff

The change optimizes hash reads on the FastURL path while preserving native hash writes and request-target fragment exclusion; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: pi0, pi0x

Poem

A rabbit checked the fragment trail,
And found the hash where URLs sail.
Fast paths kept the string serene,
Native paths showed what lay unseen.
Tests hopped after, all was green.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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 change: avoiding full URL parsing when reading hash on the fast path.
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…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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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