fix: handle relative Location URLs in redirect rewriting (#20)

[guoyangzhen]

Linked issue

Closes #20

Description

When a proxied server responds with a relative URL in the Location header (e.g., Location: /api/books/1 for 201 Created), the proxy throws:

Uncaught TypeError: Invalid URL

This happens because new URL(proxyRes.headers.location) on line 38 doesn't provide a base URL. Per RFC 9110, the Location header is allowed to contain a relative URI-reference.

Fix

Pass target as the base URL to the URL constructor:

- const u = new URL(proxyRes.headers.location);
+ const u = new URL(proxyRes.headers.location, target);

This resolves relative paths against the proxy target, which is the correct behavior for a reverse proxy.

Summary by CodeRabbit

• Bug Fixes

  • Better handling of relative redirects in proxied responses: Location headers are now resolved against the target and rewritten so redirected URLs become absolute and honor configured host/protocol rewrite settings.

• Tests

  • Added tests covering relative-URL redirect resolution and rewrite behavior to ensure preserved paths and query strings when applying host rewrites.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1471ea67-072b-4cc2-8db3-c23a4e9e7459

📥 Commits

Reviewing files that changed from the base of the PR and between c107a09 and 4cc41c8.

📒 Files selected for processing (1)

• test/middleware/web-outgoing.test.ts

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📝 Walkthrough

Walkthrough

setRedirectHostRewrite now resolves Location response headers against the proxy target by using new URL(proxyRes.headers.location, target), so relative Location values (e.g., /api/books/1) are parsed and rewritten correctly.

Changes

Cohort / File(s)	Summary
Redirect Host Rewrite src/middleware/web-outgoing.ts	Build redirected URL with new URL(proxyRes.headers.location, target) to correctly resolve relative Location headers against the proxy target.
Tests (added) test/middleware/web-outgoing.test.ts	Added tests verifying relative Location headers (e.g., /api/books/1, /redirect/here?foo=bar) are rewritten into absolute URLs using the configured hostRewrite.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• fix: handle relative Location URLs in redirect rewriting (#20) #104 — Makes the same change: resolve relative Location header values with new URL(proxyRes.headers.location, target) and adds matching tests.

Poem

🐰 A relative path once caused a plight,
I fed it a base and made it right,
From /api to http://ext-manual.com it’d roam,
Now redirects find their proper home,
Hoppity-hop, the headers sing tonight! 🥕

🚥 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 accurately describes the main change: handling relative Location URLs in redirect rewriting, which directly matches the core fix in the PR.
Linked Issues check	✅ Passed	The PR successfully addresses issue #20 by passing the proxy target as a base to the URL constructor when parsing the Location header, enabling correct handling of relative redirect URLs.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the issue: modification to URL constructor call and corresponding test cases for relative Location URL handling.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[pi0]

thanks. AI automation detected i have double checked changes.