Fix RSS discovery for direct feed URLs and rel=self links

[JulienTant]

Summary

• When a URL already returns a feed content-type (application/rss+xml, application/atom+xml, application/feed+json), DiscoverFeedURL now returns it directly instead of trying to parse HTML
• Added fallback to check rel="self" link tags in addition to rel="alternate", since some feeds (e.g. TechCrunch tag feeds) use self-referencing links
• Added two new unit tests covering both cases

Credit

Based on upstream Hyaxia/blogwatcher#14 by @carlotran4, adapted to our fork's patterns (context threading, testify, error handling in tests, etc.).

Test plan

• TestDiscoverFeedURL_XMLContentType - verifies direct feed URL return for RSS content-type
• TestDiscoverFeedURL_RelSelf - verifies discovery via rel="self" link tags
• Full test suite passes (24 tests)
• golangci-lint run reports 0 issues

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Improved RSS feed discovery with Content-Type header inspection and additional feed link pattern support for more reliable feed identification.

[coderabbitai]

📝 Walkthrough

Walkthrough

The DiscoverFeedURL function now inspects the HTTP response's Content-Type header and returns the URL directly if it matches a feed type. When parsing HTML for feed links, it adds fallback logic to search for rel='self' links when rel='alternate' links are not found. Two new test cases validate this behavior.

Changes

Cohort / File(s)	Summary
Feed Discovery Logic internal/rss/rss.go	Modified DiscoverFeedURL to check Content-Type header for feed types (application/rss+xml, application/atom+xml, application/feed+json) and return directly on match. Added fallback to search link[rel='self'][type='<feedType>'] when rel='alternate' links are absent.
Discovery Tests internal/rss/rss_test.go	Added test case for direct RSS response with explicit Content-Type: application/rss+xml; charset=UTF-8. Added test case for rel='self' link discovery and URL resolution.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 Hop through the feeds with better sight,
Content-Types guide us to the right,
When alternate links don't appear,
Self-relations bring us cheer! 🔗

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main changes: fixing RSS discovery for direct feed URLs and rel=self links, which are the core improvements in the changeset.
Description check	✅ Passed	The description covers all required template sections with sufficient detail: clear summary of changes, explicit test plan with checkbox completion, and proper credit attribution.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rss-discovery-xml-content-type-and-rel-self

---

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

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@internal/rss/rss.go`:
- Around line 95-101: The mime.ParseMediaType call currently ignores parse
errors; update the code around mime.ParseMediaType in internal/rss/rss.go so
that when err != nil you do not silently continue but instead handle it per
project rule — either log the parse error with the package's logger (including
context like the contentType and candidate blogURL) or propagate the error to
the caller (adjust the function signature/returns if needed). Keep the existing
mediaType checks (application/rss+xml, application/atom+xml,
application/feed+json) unchanged when err == nil; only add explicit error
handling for the ParseMediaType error path.

🪄 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: defaults

Review profile: CHILL

Plan: Pro

Run ID: fbc279ac-b94f-4ce6-a7bf-8a65b911f7ed

📥 Commits

Reviewing files that changed from the base of the PR and between 2972f35 and 22c44d9.

📒 Files selected for processing (2)

• internal/rss/rss.go
• internal/rss/rss_test.go