fix(intent): decode legacy __ scoped-package slugs (500 on indexed registry URLs)

[dearlordylord]

Problem

Legacy registry links encoded the scope separator as __ (@scope/name → @scope__name) and those URLs are still indexed by search engines. Commit 0f55472 switched the slug codec to encodeURIComponent/decodeURIComponent and dropped the old __→/ decode. Landing on a legacy __ URL now runs the package lookup with the literal @scope__name, which fails the npm package-name regex → the query errors → HTTP 500.

Reproduces for every scoped package via its legacy URL, e.g.:

curl -so /dev/null -w "%{http_code}\n" https://tanstack.com/intent/registry/%40apollo__client         # 500
curl -so /dev/null -w "%{http_code}\n" https://tanstack.com/intent/registry/%2540apollo%252Fclient     # 200 (canonical)

Fix

Restore the __→/ scope-separator back-compat in decodePackageNameSlug, mirroring the still-present logic in src/routes/stats/npm/-utils.ts (decodePackageName). The guard is narrow — startsWith('@') && includes('__') && !includes('/') — so:

• legacy @firfi__quint-connect → @firfi/quint-connect
• @depup__trpc__server → @depup/trpc__server (only the scope separator is restored)
• unscoped tanstack__intent → unchanged
• canonical %2F / double-encoded slugs → unchanged

Tests

Added legacy-slug cases to tests/route-encoding.test.ts.

Local gate (all green): pnpm test (tsc + oxlint --type-aware + tsx --test) and pnpm build.

Not included (open to feedback)

A 301 redirect from the legacy __ slug to the canonical encodeURIComponent URL would additionally consolidate SEO. Left out here because the router's double-encoding makes a redirect loop-prone; this decoder fix alone stops the 500s. Happy to add the redirect if preferred.

Closes #1050

Summary by CodeRabbit

• Bug Fixes
  • Improved decoding of package route links, including legacy links for scoped packages.
  • Restored compatibility with older links that use encoded scope separators.
  • Prevented unnecessary repeated decoding and preserved double underscores within package names.
  • Ensured unscoped package names containing double underscores continue to display correctly.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b41f0875-abfa-42f5-be71-152d68ec88a9

📥 Commits

Reviewing files that changed from the base of the PR and between 3b4add9 and 4c4df12.

📒 Files selected for processing (2)

• src/utils/route-encoding.ts
• tests/route-encoding.test.ts

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📝 Walkthrough

Walkthrough

decodePackageNameSlug now stops when decoding produces no change and converts legacy scoped slugs using __ into /. Tests cover percent-encoded inputs, preservation of internal __, and unscoped package names.

Changes

Route encoding compatibility

Layer / File(s)	Summary
Legacy scoped slug normalization and validation src/utils/route-encoding.ts, tests/route-encoding.test.ts	Decoding restores the leading legacy scope separator for applicable @scope__name slugs, avoids redundant passes, and tests encoded and unscoped cases.

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

Possibly related issues

• Intent registry: legacy __ scoped-package URLs return HTTP 500 (indexed by Google, no redirect to canonical) #1050 — Directly tracks the legacy __ scoped-package slug decoding behavior addressed by this change.

🚥 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 matches the main change: backward-compatible decoding of legacy __ scoped-package slugs causing 500s on indexed registry URLs.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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