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Merged
Adron merged 2 commits into from
Sep 17, 2026
Merged

fix(feed): reconcile in-place row updates in the feed #107

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bf04d2b
fix(feed): reconcile in-place row updates in the feed
Adron Sep 16, 2026
b053cca
Merge origin/main into fix/feedview-inplace-row-updates
Adron Sep 17, 2026
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8 changes: 8 additions & 0 deletions InterlinedList.xcodeproj/project.pbxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,8 @@
A5C47F6A46E3CE8708789CB2 /* PublicBrowse.swift in Sources */ = {isa = PBXBuildFile; fileRef = 74B5AC4D76899CEAF620E402 /* PublicBrowse.swift */; };
ADE33267E8D212F2863B1ABB /* APIClientSearchUsersTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 93B62D89758287A728A56C9B /* APIClientSearchUsersTests.swift */; };
B1C1D1E1F1A10001 /* DataCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = B1C1D1E1F1A10002 /* DataCache.swift */; };
FEED105A0000000000000001 /* FeedMerge.swift in Sources */ = {isa = PBXBuildFile; fileRef = FEED105A0000000000000002 /* FeedMerge.swift */; };
FEED105A0000000000000003 /* FeedMergeTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = FEED105A0000000000000004 /* FeedMergeTests.swift */; };
B1C1D1E1F1A10003 /* AppDataStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = B1C1D1E1F1A10004 /* AppDataStore.swift */; };
AB80F1A1C0DE000000000003 /* ThemePreferenceTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = AB80F1A1C0DE000000000004 /* ThemePreferenceTests.swift */; };
B1C1D1E1F1A10005 /* SkeletonBlock.swift in Sources */ = {isa = PBXBuildFile; fileRef = B1C1D1E1F1A10006 /* SkeletonBlock.swift */; };
Expand Down Expand Up @@ -415,6 +417,8 @@
AC8F31A0EA9ADA8C6827A16C /* APIClient+AppSettings.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "APIClient+AppSettings.swift"; sourceTree = "<group>"; };
AE452BC01A7461AF5199FFE6 /* AIJSON.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = AIJSON.swift; sourceTree = "<group>"; };
B1C1D1E1F1A10002 /* DataCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DataCache.swift; sourceTree = "<group>"; };
FEED105A0000000000000002 /* FeedMerge.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = FeedMerge.swift; sourceTree = "<group>"; };
FEED105A0000000000000004 /* FeedMergeTests.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = FeedMergeTests.swift; sourceTree = "<group>"; };
B1C1D1E1F1A10004 /* AppDataStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDataStore.swift; sourceTree = "<group>"; };
B1C1D1E1F1A10006 /* SkeletonBlock.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SkeletonBlock.swift; sourceTree = "<group>"; };
B1C1D1E1F1A10008 /* FeedSkeletonView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FeedSkeletonView.swift; sourceTree = "<group>"; };
Expand Down Expand Up @@ -640,6 +644,7 @@
966A4B3A93B371DF62CDE9B4 /* APIClient+ListContributors.swift */,
A3C3D3E3F3A30056 /* URLSessionProtocol.swift */,
B1C1D1E1F1A10002 /* DataCache.swift */,
FEED105A0000000000000002 /* FeedMerge.swift */,
B1C1D1E1F1A10004 /* AppDataStore.swift */,
D0A1D0A1D0A10002 /* OAuthCoordinator.swift */,
1F84433332486544DA15C7BA /* APIClient+Documents.swift */,
Expand Down Expand Up @@ -868,6 +873,7 @@
BA27DCE269D834AE6F1C569D /* MuteStoreTests.swift */,
AB80F1A1C0DE000000000004 /* ThemePreferenceTests.swift */,
8E384ED04860E87973898F89 /* DocumentSyncMergeTests.swift */,
FEED105A0000000000000004 /* FeedMergeTests.swift */,
D42A88BDF9EB795F41CF2F64 /* DocumentSyncOutboxTests.swift */,
126B48E798CB7064F46382CC /* DocumentSyncConflictTests.swift */,
D2113D42FDEA77E3C0E4974E /* ServerLimitsStoreTests.swift */,
Expand Down Expand Up @@ -1015,6 +1021,7 @@
A3C3D3E3F3A30053 /* DocumentsView.swift in Sources */,
A3C3D3E3F3A30055 /* URLSessionProtocol.swift in Sources */,
B1C1D1E1F1A10001 /* DataCache.swift in Sources */,
FEED105A0000000000000001 /* FeedMerge.swift in Sources */,
B1C1D1E1F1A10003 /* AppDataStore.swift in Sources */,
B1C1D1E1F1A10005 /* SkeletonBlock.swift in Sources */,
B1C1D1E1F1A10007 /* FeedSkeletonView.swift in Sources */,
Expand Down Expand Up @@ -1199,6 +1206,7 @@
C8AFF749A154E5F96FB77DE2 /* APIClientSessionsTests.swift in Sources */,
FC004747AE60A6796DAD36AB /* APIClientDocumentSyncTests.swift in Sources */,
4A2F1A2E2FB0B4BC857F9E30 /* DocumentSyncMergeTests.swift in Sources */,
FEED105A0000000000000003 /* FeedMergeTests.swift in Sources */,
1C47F69DF0848EF0C45C51EE /* DocumentSyncModelTests.swift in Sources */,
213A17C03007A464190DB5D6 /* APIClientMessageByIdTests.swift in Sources */,
C6197F8F1B52DAE1B1D4A2F1 /* AppDeepLinkParseTests.swift in Sources */,
Expand Down
20 changes: 19 additions & 1 deletion InterlinedList/Services/AppDataStore.swift
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Expand Up @@ -7,7 +7,16 @@ import Foundation

@MainActor
final class AppDataStore: ObservableObject {
@Published private(set) var feedMessages: [Message] = []
@Published private(set) var feedMessages: [Message] = [] {
didSet { feedRevision &+= 1 }
}

/// Bumped on every mutation of `feedMessages`, in-place row edits included.
/// `Message`'s `Equatable` is identity-based (`id` only), so neither the array
/// nor its `count` moves when a row's content is replaced — a view mirroring the
/// feed has nothing else to observe.
@Published private(set) var feedRevision = 0

@Published private(set) var feedLoading = true
@Published private(set) var feedError: String?

Expand Down Expand Up @@ -483,6 +492,15 @@ final class AppDataStore: ObservableObject {
saveFeedCache()
}

/// Replaces an already-loaded row with a newer copy of itself. Unknown id: no-op —
/// the feed page is a window, not the whole timeline, so a message that has scrolled
/// out of it is not an error.
func updateFeedMessage(_ message: Message) {
guard let index = feedMessages.firstIndex(where: { $0.id == message.id }) else { return }
feedMessages[index] = message
saveFeedCache()
}

/// Replaces the link previews on one already-inserted feed message, so the row
/// a publish just added can show its card as soon as the metadata refresh lands.
///
Expand Down
37 changes: 37 additions & 0 deletions InterlinedList/Services/FeedMerge.swift
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@@ -0,0 +1,37 @@
//
// FeedMerge.swift
// InterlinedList
//

import Foundation

/// Reconciles the store's feed page into a view's working copy of the feed.
///
/// The working copy is not a plain mirror of `AppDataStore.feedMessages`: pagination
/// appends pages the store never sees, so the store's page has to be merged into it
/// rather than replace it. Rows already held keep their position (and with it the
/// scroll position); a row the store has re-sent replaces the held copy in place, so
/// an edit to an existing row is visible without a reload.
enum FeedMerge {
struct Result {
let messages: [Message]
/// Rows this merge inserted or replaced — the ones whose derived per-row
/// state (dig counts) needs re-seeding. Empty means nothing moved.
let changed: [Message]
}

static func merge(existing: [Message], incoming: [Message]) -> Result {
let incomingById = Dictionary(incoming.map { ($0.id, $0) }, uniquingKeysWith: { _, last in last })
var merged = existing
var replaced: [Message] = []
for index in merged.indices {
guard let updated = incomingById[merged[index].id] else { continue }
merged[index] = updated
replaced.append(updated)
}
let existingIds = Set(existing.map(\.id))
let inserted = incoming.filter { !existingIds.contains($0.id) }
merged.insert(contentsOf: inserted, at: 0)
return Result(messages: merged, changed: inserted + replaced)
}
}
15 changes: 8 additions & 7 deletions InterlinedList/Views/FeedView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,9 @@ struct FeedView: View {
if let index = messages.firstIndex(where: { $0.id == updated.id }) {
messages[index] = updated
}
// The working copy can hold rows the store's page never saw, so the
// local write above stays; this keeps the store and its cache in step.
store.updateFeedMessage(updated)
}
}
.alert("Delete message?", isPresented: Binding(
Expand Down Expand Up @@ -392,7 +395,7 @@ struct FeedView: View {
if authState.isLoggedIn { Task { await loadMessages() } }
}
return nav
.onChange(of: store.feedMessages.count) { _, _ in
.onChange(of: store.feedRevision) { _, _ in
guard !showOnlyMine && tagFilter == nil else { return }
if !syncedFromStore {
let msgs = store.feedMessages
Expand All @@ -401,12 +404,10 @@ struct FeedView: View {
isLoading = false
syncedFromStore = !msgs.isEmpty
} else {
let existingIds = Set(messages.map { $0.id })
let newMessages = store.feedMessages.filter { !existingIds.contains($0.id) }
if !newMessages.isEmpty {
messages.insert(contentsOf: newMessages, at: 0)
initDigStates(from: newMessages)
}
let result = FeedMerge.merge(existing: messages, incoming: store.feedMessages)
guard !result.changed.isEmpty else { return }
messages = result.messages
initDigStates(from: result.changed)
}
}
.onChange(of: store.feedLoading) { _, loading in
Expand Down
91 changes: 89 additions & 2 deletions InterlinedListTests/ServiceTests/AppDataStoreTests.swift
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Expand Up @@ -82,6 +82,92 @@ final class AppDataStoreTests: XCTestCase {
wait(for: [countIncreased], timeout: 1.0)
}

// MARK: - updateFeedMessage

func test_updateFeedMessage_replacesTheRowContent() {
sut.insertFeedMessage(makeMessage(id: "a", content: "before"))
sut.updateFeedMessage(makeMessage(id: "a", content: "after"))
XCTAssertEqual(sut.feedMessages.first?.content, "after")
}

func test_updateFeedMessage_keepsCountAndOrder() {
sut.insertFeedMessage(makeMessage(id: "a"))
sut.insertFeedMessage(makeMessage(id: "b"))
sut.updateFeedMessage(makeMessage(id: "a", content: "edited"))
XCTAssertEqual(sut.feedMessages.map(\.id), ["b", "a"])
XCTAssertEqual(sut.feedMessages.last?.content, "edited")
}

func test_updateFeedMessage_leavesOtherRowsAlone() {
sut.insertFeedMessage(makeMessage(id: "a", content: "a-content"))
sut.insertFeedMessage(makeMessage(id: "b", content: "b-content"))
sut.updateFeedMessage(makeMessage(id: "b", content: "edited"))
XCTAssertEqual(sut.feedMessages.last?.content, "a-content")
}

func test_updateFeedMessage_unknownId_isANoOp() {
sut.insertFeedMessage(makeMessage(id: "a", content: "kept"))
sut.updateFeedMessage(makeMessage(id: "ghost", content: "ignored"))
XCTAssertEqual(sut.feedMessages.map(\.id), ["a"])
XCTAssertEqual(sut.feedMessages.first?.content, "kept")
}

// MARK: - feedRevision

/// The whole point of the revision: `Message` compares by id, so neither the
/// array nor its count moves when a row is edited in place.
func test_feedRevision_movesWhenARowIsEditedInPlace() {
sut.insertFeedMessage(makeMessage(id: "a", content: "before"))
let before = sut.feedRevision
let countBefore = sut.feedMessages.count
sut.updateFeedMessage(makeMessage(id: "a", content: "after"))
XCTAssertEqual(sut.feedMessages.count, countBefore)
XCTAssertGreaterThan(sut.feedRevision, before)
}

func test_feedRevision_movesWhenARowIsInserted() {
let before = sut.feedRevision
sut.insertFeedMessage(makeMessage(id: "a"))
XCTAssertGreaterThan(sut.feedRevision, before)
}

func test_feedRevision_doesNotMoveForAnUnknownId() {
sut.insertFeedMessage(makeMessage(id: "a"))
let before = sut.feedRevision
sut.updateFeedMessage(makeMessage(id: "ghost"))
XCTAssertEqual(sut.feedRevision, before)
}

// MARK: - store mutation reaching the feed's working copy

/// End of the chain the bug broke: the store edits a row, and the copy `FeedView`
/// renders from picks the edit up through `FeedMerge` without a reload.
func test_storeRowEdit_reachesTheViewsWorkingCopy() {
sut.insertFeedMessage(makeMessage(id: "a", content: "before"))
let viewCopy = sut.feedMessages
let revisionBefore = sut.feedRevision

sut.updateFeedMessage(makeMessage(id: "a", content: "after"))

XCTAssertGreaterThan(sut.feedRevision, revisionBefore)
let merged = FeedMerge.merge(existing: viewCopy, incoming: sut.feedMessages)
XCTAssertEqual(merged.messages.count, 1)
XCTAssertEqual(merged.messages.first?.content, "after")
}

/// The view's copy runs ahead of the store once pagination has appended a page;
/// a store edit must not drop those rows.
func test_storeRowEdit_keepsPaginatedRowsTheStoreNeverSaw() {
sut.insertFeedMessage(makeMessage(id: "p1", content: "before"))
let viewCopy = sut.feedMessages + [makeMessage(id: "p2"), makeMessage(id: "p3")]

sut.updateFeedMessage(makeMessage(id: "p1", content: "after"))

let merged = FeedMerge.merge(existing: viewCopy, incoming: sut.feedMessages)
XCTAssertEqual(merged.messages.map(\.id), ["p1", "p2", "p3"])
XCTAssertEqual(merged.messages.first?.content, "after")
}

// MARK: - reset

func test_reset_clearsFeedMessages() {
Expand Down Expand Up @@ -352,8 +438,9 @@ final class AppDataStoreTests: XCTestCase {

// MARK: - Helpers

private func makeMessage(id: String, linkMetadata: LinkMetadata? = nil) -> Message {
Message(id: id, content: "test", publiclyVisible: true,
private func makeMessage(id: String, content: String = "test",
linkMetadata: LinkMetadata? = nil) -> Message {
Message(id: id, content: content, publiclyVisible: true,
userId: "u1", createdAt: "2026-01-01T00:00:00Z",
updatedAt: nil, user: nil, imageUrls: nil, videoUrls: nil,
linkMetadata: linkMetadata, parentId: nil, scheduledAt: nil,
Expand Down
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