Fix traverseCollection() for inline CollectionPage without id #550

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Merged

Jan 31, 2026

CHANGES.md

-Original file line number
+Diff line change
@@ Expand Up / @@ -8,6 +8,15 @@ Version 1.9.5 @@
     To be released.
+    ### @fedify/fedify
+     -  Fixed `traverseCollection()` yielding no items when a `Collection` has
+        an inline `CollectionPage` in its `first` property without an explicit
+        `id`.  This is common in Mastodon's `replies` collections.  The function
+        previously used `collection.firstId` to determine pagination, which
+        returned `null` for inline pages without an `id`, causing it to
+        incorrectly fall into the non-paginated branch.
     Version 1.9.4
     -------------
@@ Expand Down @@

-Original file line number
+Diff line change
@@ -0,0 +1,13 @@
+    {
+      "@context": "https://www.w3.org/ns/activitystreams",
+      "id": "https://example.com/inline-paged-collection",
+      "type": "Collection",
+      "first": {
+        "type": "CollectionPage",
+        "partOf": "https://example.com/inline-paged-collection",
+        "next": "https://example.com/inline-paged/a",
+        "items": [
+          { "type": "Note", "content": "Inline first note" }
+        ]
+      }
+    }

packages/fedify/src/testing/fixtures/example.com/inline-paged/a.json

-Original file line number
+Diff line change
@@ -0,0 +1,8 @@
+    {
+      "@context": "https://www.w3.org/ns/activitystreams",
+      "type": "CollectionPage",
+      "partOf": "https://example.com/inline-paged-collection",
+      "items": [
+        { "type": "Note", "content": "Inline second note" }
+      ]
+    }

packages/fedify/src/vocab/lookup.test.ts

-Original file line number
+Diff line change
@@ -1,5 +1,6 @@
     import { assertEquals, assertInstanceOf, assertRejects } from "@std/assert";
     import fetchMock from "fetch-mock";
+    import { deepStrictEqual } from "node:assert";
     import { mockDocumentLoader } from "../testing/docloader.ts";
     import { test } from "../testing/mod.ts";
     import { lookupObject, traverseCollection } from "./lookup.ts";
@@ Expand Down Expand Up / @@ -260,6 +261,21 @@ test("traverseCollection()", { @@
           new Note({ content: "This is a third simple note" }),
         ],
       );
+      // Inline-paged collection (CollectionPage embedded without id, with next)
+      const inlinePagedCollection = await lookupObject(
+        "https://example.com/inline-paged-collection",
+        options,
+      );
+      assertInstanceOf(inlinePagedCollection, Collection);
+      deepStrictEqual(
+        await Array.fromAsync(
+          traverseCollection(inlinePagedCollection, options),
+        ),
+        [
+          new Note({ content: "Inline first note" }),
+          new Note({ content: "Inline second note" }),
+        ],
+      );
     });
     test("FEP-fe34: lookupObject() cross-origin security", {
@@ Expand Down @@

packages/fedify/src/vocab/lookup.ts

-Original file line number
+Diff line change
@@ Expand Up / @@ -290,14 +290,14 @@ export async function* traverseCollection( @@
       collection: Collection,
       options: TraverseCollectionOptions = {},
     ): AsyncIterable<Object | Link> {
-      if (collection.firstId == null) {
+      const interval = Temporal.Duration.from(options.interval ?? { seconds: 0 })
+        .total("millisecond");
+      let page = await collection.getFirst(options);
+      if (page == null) {
         for await (const item of collection.getItems(options)) {
           yield item;
         }
       } else {
-        const interval = Temporal.Duration.from(options.interval ?? { seconds: 0 })
-          .total("millisecond");
-        let page = await collection.getFirst(options);
         while (page != null) {
           for await (const item of page.getItems(options)) {
             yield item;
@@ Expand Down @@

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