fix(vercel): strip trailing slash from prerendered route overrides

[thribhuvan003]

🔗 Linked issue

resolves #4392

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

prerendering a route with a trailing slash (e.g. /slash/) emits a Build Output override whose path keeps the slash — "slash/index.html": { "path": "slash/" } — and vercel doesn't match override paths like that, so the route falls through to the server function instead of being served statically (repro + live deploy in #4392).

this strips the trailing slash the same way the leading one is already stripped, so the override becomes "path": "slash". the root route is unaffected (/ still maps to ""). extended the vercel:web preset test with a prerendered /slash/ route.

the same line exists on the v2 branch (src/presets/vercel/utils.ts:166) — happy to open a backport if useful.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[vercel]

@thribhuvan003 is attempting to deploy a commit to the Nitro Team on Vercel.

A member of the Team first needs to authorize it.

[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: 70adf396-d4e2-4075-8d7e-8000e1ecad32

📥 Commits

Reviewing files that changed from the base of the PR and between 1b49316 and 762a852.

📒 Files selected for processing (2)

• src/presets/vercel/utils.ts
• test/unit/vercel-overrides.test.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• test/unit/vercel-overrides.test.ts
• src/presets/vercel/utils.ts

---

📝 Walkthrough

Walkthrough

This change centralizes Vercel prerender override generation, strips surrounding slashes, skips directory-index and invalid self-referential mappings, and adds preset and unit coverage for these cases.

Changes

Vercel override mapping

Layer / File(s)	Summary
Override generation and build integration src/presets/vercel/utils.ts	Adds getPrerenderOverrides, normalizes route paths, skips directory indexes and invalid mappings, and uses the helper during Vercel config generation.
Preset output regression coverage test/presets/fixtures/slash.ts, test/presets/vercel.test.ts	Adds a /slash handler, prerenders /slash/, and updates config and function snapshots.
Override edge-case tests test/unit/vercel-overrides.test.ts	Tests empty inputs, index routes, trailing slashes, rewritten filenames, self-referential entries, and missing filenames.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% 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
Title check	✅ Passed	The title is a valid conventional commit and clearly matches the Vercel trailing-slash fix.
Description check	✅ Passed	The description directly explains the regression, fix, and test coverage, so it is clearly on-topic.
Linked Issues check	✅ Passed	The code strips trailing slashes from prerender override paths and adds regression tests, matching #4392.
Out of Scope Changes check	✅ Passed	All file changes support the Vercel override fix and tests; no unrelated changes are evident.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Fix failing CI checks

🧪 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.}

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

src/presets/vercel/utils.ts (1)

397-413: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Extract this internal mapping helper into a dedicated module.

This adds more logic to an already 400+ LoC utility module. Move the helper and regexes to src/presets/vercel/_overrides.ts and import it directly.

As per coding guidelines, “Split logic across files; avoid long single-file modules (>200 LoC). Use _* prefix for internal files.”

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/presets/vercel/utils.ts` around lines 397 - 413, Extract
getPrerenderOverrides and its related SURROUNDING_SLASH_RE and INDEX_FILE_RE
definitions from the utility module into the internal
src/presets/vercel/_overrides.ts module, then import and use
getPrerenderOverrides from that module at its existing call sites. Preserve the
helper’s current mapping behavior and keep the underscore-prefixed module
internal.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/presets/vercel/utils.ts`:
- Around line 400-407: Normalize the route and file name in the
prerenderedRoutes loop before comparing them, then skip the override when the
normalized keys are equal via file === path, covering equivalent spellings such
as “/foo/” and “/foo”. Update the existing unit test for override generation to
include this self-targeting normalized case.

---

Nitpick comments:
In `@src/presets/vercel/utils.ts`:
- Around line 397-413: Extract getPrerenderOverrides and its related
SURROUNDING_SLASH_RE and INDEX_FILE_RE definitions from the utility module into
the internal src/presets/vercel/_overrides.ts module, then import and use
getPrerenderOverrides from that module at its existing call sites. Preserve the
helper’s current mapping behavior and keep the underscore-prefixed module
internal.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: e3d53770-a9df-449e-97b5-e7e11ac02e4f

📥 Commits

Reviewing files that changed from the base of the PR and between 44908da and 95248bb.

📒 Files selected for processing (3)

• src/presets/vercel/utils.ts
• test/presets/vercel.test.ts
• test/unit/vercel-overrides.test.ts

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/nitro@4412

commit: 762a852