Following an account brings its earlier posts to its profile

Once a follow holds, OutboxBackfill reads the account's latest public posts from its outbox's first page (twenty at
most, once a day) and keeps them as any fetched post: its profile shows them at once instead of only what it posts from
then on. Homes still get only what arrives afterwards, as on Mastodon. Announces and other servers' objects in the
outbox are left out. Checked live against Mastodon (scenarios/pins.sh, now 9 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub.Tests/Federation/BackfillTests.cs

@@ -0,0 +1,78 @@
+using MongoDB.Entities;
+
+using PrivaPub.Federation.Actors;
+using PrivaPub.Models.Jobs;
+using PrivaPub.Models.Post;
+using PrivaPub.Models.Social;
+using PrivaPub.Tests.Support;
+
+using System.Text.Json.Nodes;
+
+namespace PrivaPub.Tests.Federation
+{
+	// a follow that holds reads the account's latest public posts from its outbox, so its profile is not empty
+	[Trait("Category", "Integration")]
+	public sealed class BackfillTests : IAsyncLifetime
+	{
+		Harness _harness;
+
+		public async ValueTask InitializeAsync()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			_harness = await Harness.Start();
+		}
+
+		public async ValueTask DisposeAsync()
+		{
+			if (_harness != default)
+				await _harness.DisposeAsync();
+		}
+
+		[Fact]
+		public async Task An_accepted_follow_reads_the_accounts_latest_public_posts_from_its_outbox()
+		{
+			var token = TestContext.Current.CancellationToken;
+			var (_, alice) = await _harness.Persona("alice");
+			var bob = new RemoteActor(_harness.Peer, "bob");
+			var mallory = new RemoteActor(_harness.Peer, "mallory", _harness.Peer.B);
+			var origin = new Uri(bob.Id).GetLeftPart(UriPartial.Authority);
+			JsonObject Note(string id, string text, RemoteActor author) => new()
+			{
+				["id"] = id, ["type"] = "Note", ["attributedTo"] = author.Id, ["content"] = $"<p>{text}</p>",
+				["to"] = new JsonArray("https://www.w3.org/ns/activitystreams#Public"), ["published"] = DateTime.UtcNow.ToString("O")
+			};
+			var older = $"{origin}/notes/{Guid.NewGuid():N}";
+			var newer = $"{origin}/notes/{Guid.NewGuid():N}";
+			var notBobs = $"{new Uri(mallory.Id).GetLeftPart(UriPartial.Authority)}/notes/{Guid.NewGuid():N}";
+			_harness.Peer.Serve(new Uri(older).AbsolutePath, Note(older, "an older post", bob).ToJsonString());
+			_harness.Peer.Serve(new Uri(newer).AbsolutePath, Note(newer, "a newer post", bob).ToJsonString());
+			_harness.Peer.Serve(new Uri(bob.Id).AbsolutePath + "/outbox", new JsonObject
+			{
+				["id"] = bob.Id + "/outbox", ["type"] = "OrderedCollection", ["totalItems"] = 4,
+				["orderedItems"] = new JsonArray(
+					new JsonObject { ["type"] = "Create", ["object"] = Note(newer, "a newer post", bob) },
+					new JsonObject { ["type"] = "Announce", ["object"] = notBobs },
+					new JsonObject { ["type"] = "Create", ["object"] = notBobs },
+					new JsonObject { ["type"] = "Create", ["object"] = older })
+			}.ToJsonString());
+			var account = await _harness.Remote.GetActor(bob.Id, refresh: false, token);
+			var followId = alice.ActivityUri($"follow-{Guid.NewGuid():N}");
+			await DB.Default.SaveAsync(new Following
+			{
+				AvatarId = alice.Id, TargetActorURI = bob.Id, TargetAccountId = account.ID, State = FollowState.Requested, FollowActivityURI = followId
+			}, token);
+
+			await _harness.Deliver(bob, "/human-centipede", new JsonObject
+			{
+				["id"] = $"{bob.Id}#accept-{Guid.NewGuid():N}", ["type"] = "Accept", ["actor"] = bob.Id,
+				["object"] = new JsonObject { ["id"] = followId, ["type"] = "Follow", ["actor"] = alice.Uri, ["object"] = bob.Id }
+			});
+			var job = await DB.Default.Find<Job>().Match(j => j.Kind == JobKind.BackfillOutbox && j.Payload == bob.Id).ExecuteSingleAsync(token);
+			await new OutboxBackfill(_harness.Db, _harness.Remote, _harness.RemotePosts).Handle(job, token);
+
+			var held = (await DB.Default.Find<Post>().Match(p => p.ActorURI == bob.Id).ExecuteAsync(token)).Select(p => p.ObjectURI).ToHashSet();
+			Assert.Equal(new HashSet<string> { older, newer }, held);
+			Assert.False(await DB.Default.Find<Post>().Match(p => p.ObjectURI == notBobs).ExecuteAnyAsync(token));
+		}
+	}
+}

PrivaPub.Tests/Support/Harness.cs

@@ -62,7 +62,7 @@ namespace PrivaPub.Tests.Support
 			Handlers = new IActivityHandler[]
 			{
 				new FollowHandler(Db, Local, Remote, Delivery),
-				new AcceptHandler(Db, Local, Quotes, Approvals, Participations, Relays),
+				new AcceptHandler(Db, Local, Quotes, Approvals, Participations, Relays, Queue),
 				new RejectHandler(Db, Local, Quotes, Approvals, Participations, Relays),
 				new UndoHandler(Db, Local, Reactions),
 				new LikeHandler(Db, Reactions),

PrivaPub.Tests/Support/RemoteActor.cs

@@ -41,6 +41,7 @@ namespace PrivaPub.Tests.Support
 				["preferredUsername"] = Name,
 				["inbox"] = Id + "/inbox",
 				["followers"] = Id + "/followers",
+				["outbox"] = Id + "/outbox",
 				["featured"] = Id + "/featured",
 				["publicKey"] = new JsonObject
 				{