Fix traverseCollection() for inline CollectionPage without id

[moreal]

Summary

traverseCollection() used collection.firstId to determine whether a collection is paginated. When a server (e.g. Mastodon) embeds a CollectionPage inline in the first property without an explicit id, firstId returns null, causing the function to enter the non-paginated branch and call collection.getItems() — which yields nothing because items live on the page, not the collection itself.

Replace the firstId check with an actual getFirst() call so that inline CollectionPage objects are correctly detected and traversed.

Related issue

I couldn't find related issue when searching with following queries:

• label:type/bug
• traverse
• collection

Changes

List the specific modifications made in this PR.
Focus on what was changed without going into detail about impact.

• Added regression test for inline paged collection.
• Let traverseCollection call Collection.getFirst() instead to check only Collection.firstId.

Benefits

traverseCollection can handle collections with a first property without id property. (e.g., Mastodon Note.replies)

Checklist

• Did you add a changelog entry to the CHANGES.md?
• Did you write some relevant docs about this change (if it's a new feature)?
• Did you write a regression test to reproduce the bug (if it's a bug fix)?
• Did you write some tests for this change (if it's a new feature)?
• Did you run mise test on your machine?
  • In 1.9-maintenance branch, there is no test mise task. So I run deno task test, pnpm run test, pnpm run test:bun

Additional notes

Mastodon Note.replies example:

fedify lookup --raw 'https://social.silicon.moe/@moreal/115990520528477317' | jq '.replies'
✔ Fetched object: https://social.silicon.moe/@moreal/115990520528477317.
{
  "id": "https://social.silicon.moe/users/moreal/statuses/115990520528477317/replies",
  "type": "Collection",
  "first": {
    "type": "CollectionPage",
    "next": "https://social.silicon.moe/users/moreal/statuses/115990520528477317/replies?min_id=115990521217861925&page=true",
    "partOf": "https://social.silicon.moe/users/moreal/statuses/115990520528477317/replies",
    "items": [
      "https://social.silicon.moe/users/moreal/statuses/115990521217861925"
    ]
  }
}
✔ Successfully fetched the object.

[gemini-code-assist]

Summary of Changes

Hello @moreal, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical bug in the traverseCollection function, which previously failed to correctly process ActivityPub Collection objects containing an inline CollectionPage without an explicit identifier. This specific scenario, common in platforms like Mastodon for replies collections, resulted in the function incorrectly identifying such collections as non-paginated and thus yielding no items. The fix involves a refined approach to pagination detection, leveraging collection.getFirst() to accurately identify and traverse these collections, thereby improving compatibility and data retrieval for various ActivityPub implementations.

Highlights

• Bug Fix for traverseCollection: Corrected an issue where traverseCollection() failed to yield items from Collection objects that embed an inline CollectionPage without an explicit id.
• Improved Pagination Detection: The logic for determining if a collection is paginated was updated from checking collection.firstId to calling collection.getFirst(), which correctly handles inline CollectionPage objects.
• Regression Test Added: A new regression test case was introduced to ensure the correct traversal of inline paged collections, specifically addressing the scenario where CollectionPage is embedded without an id.

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[gemini-code-assist]

Code Review

This pull request provides a solid fix for an issue in traverseCollection() where inline CollectionPage objects without an id were not being handled correctly. The change to use the result of collection.getFirst() directly, instead of relying on collection.firstId, is the correct approach to solve this problem. I appreciate the inclusion of a regression test, which ensures the fix is effective and prevents future regressions. The accompanying refactoring to reduce code duplication is also a welcome improvement. The changes are well-implemented and the changelog is clearly updated. Overall, this is an excellent contribution.

[dahlia]

Good catch! Thanks!

[dahlia]

Released with 1.9.5 and 1.10.3.