[workers-shared] Add support for inline comments in _redirects files

[petebacondarwin]

Fixes #3255.

Adds support for inline comments in _redirects files using the # character. This allows developers to document complex redirect rules directly alongside the rules themselves:

/old-page /new-page 301 # Moved during site redesign
/blog/* /articles/:splat # Blog URL migration

The implementation detects inline comments by looking for any token starting with # at position 2 or later (after the required from and to tokens). This approach:

• Correctly preserves URL fragments like /page#section (no space before the #)
• Strips comments like /a /b # comment or /a /b 301 # comment
• Is backwards compatible - existing _redirects files work identically
• Handles edge cases like empty comments, multiple hashes in fragments, and absolute URLs with fragments

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• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s): docs: document inline comments in _redirects files cloudflare-docs#28171
  • Documentation not necessary because:

A picture of a cute animal (not mandatory, but encouraged)

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[changeset-bot]

🦋 Changeset detected

Latest commit: d075084

The changes in this PR will be included in the next version bump.

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[claude]

Claude finished @petebacondarwin's task —— View job

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Changeset Review

Reviewing the changeset for this PR...

Tasks

• Read changeset guidelines from .changeset/README.md
• Review .changeset/inline-comments-redirects.md
• Validate version type, changelog quality, and formatting
• Check for cute animal images
• Post review findings

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Review Results

✅ All changesets look good

The changeset .changeset/inline-comments-redirects.md is well-formatted and follows all guidelines:

• Version Type: minor is appropriate (new feature - inline comment support)
• Changelog Quality: Clear title and helpful body with usage examples
• Markdown Headers: No h1/h2/h3 headers used ✓
• Package Coverage: Correctly references @cloudflare/workers-shared
• Description: Excellent - explains what the feature is, provides examples, and notes important details about URL fragments

The changeset effectively communicates the new functionality and will create a helpful changelog entry for users.

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commit: d075084

[petebacondarwin]

The docs already state:

Lines starting with a # will be treated as comments.

I think we probably need to tweak those to also cover these new inline comments.

[petebacondarwin]

The change is in workers-shared, which is used in the backend to parse the _redirects file at deploy/runtime.
Once we land this change it won't be live in production until the backend updates its version of workers-shared.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 4 additional findings.

[vicb]

See the inline comment

Feedback addressed.