Add more logging around state restoration crash

Tusker/Screens/Timeline/TimelineViewController.swift

@@ -9,6 +9,7 @@
 import UIKit
 import Pachyderm
 import Combine
+import Sentry
 
 class TimelineViewController: UIViewController, TimelineLikeCollectionViewController, CollectionViewController, RefreshableViewController {
     let timeline: Timeline
@@ -335,7 +336,7 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         }
         loadViewIfNeeded()
         var loaded = false
-        await controller.restoreInitial {
+        await controller.restoreInitial { @MainActor in
             let hasStatusesToRestore = await loadStatusesToRestore(position: position)
             if hasStatusesToRestore {
                 applyItemsToRestore(position: position)
@@ -351,26 +352,45 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         guard !unloaded.isEmpty else {
             return true
         }
-        let statuses = await withTaskGroup(of: Status?.self) { group -> [Status] in
+        let results = await withTaskGroup(of: (String, Result<Status, Swift.Error>).self) { group -> [(String, Result<Status, Swift.Error>)] in
             for id in unloaded {
                 group.addTask {
                     do {
                         let (status, _) = try await self.mastodonController.run(Client.getStatus(id: id))
-                        return status
+                        return (id, .success(status))
                     } catch {
-                        print(error)
-                        return nil
+                        return (id, .failure(error))
                     }
                 }
             }
-            return await group.reduce(into: []) { partialResult, status in
-                if let status {
-                    partialResult.append(status)
-                }
+            return await group.reduce(into: []) { partialResult, result in
+                partialResult.append(result)
+            }
+        }
+        var statuses = [Status]()
+        for (id, result) in results {
+            switch result {
+            case .success(let status):
+                statuses.append(status)
+            case .failure(let error):
+                let crumb = Breadcrumb(level: .error, category: "TimelineViewController")
+                crumb.message = "Error loading status"
+                crumb.data = [
+                    "error": String(describing: error),
+                    "id": id
+                ]
+                SentrySDK.addBreadcrumb(crumb: crumb)
             }
         }
         await mastodonController.persistentContainer.addAll(statuses: statuses, in: mastodonController.persistentContainer.viewContext)
         
+        let crumb = Breadcrumb(level: .info, category: "TimelineViewController")
+        crumb.message = "Original position statusIDs"
+        crumb.data = [
+            "statusIDs": position.statusIDs,
+        ]
+        SentrySDK.addBreadcrumb(crumb: crumb)
+        
         // update the timeline position in case some statuses couldn't be loaded
         if let center = position.centerStatusID {
             let nearestLoadedStatusToCenter = position.statusIDs[position.statusIDs.firstIndex(of: center)!...].first(where: { id in
@@ -383,9 +403,17 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
             !unloaded.contains(id) || statuses.contains(where: { $0.id == id })
         }
         
+        let crumb2 = Breadcrumb(level: .info, category: "TimelineViewController")
+        crumb2.message = "Filtered position statusIDs"
+        crumb2.data = [
+            "statusIDs": position.statusIDs,
+        ]
+        SentrySDK.addBreadcrumb(crumb: crumb2)
+        
         return !position.statusIDs.isEmpty
     }
     
+    @MainActor
     private func applyItemsToRestore(position: TimelinePosition) {
         var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
         snapshot.appendSections([.statuses])
@@ -393,6 +421,12 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
         let centerStatusID = position.centerStatusID
         let items = position.statusIDs.map { Item.status(id: $0, collapseState: .unknown, filterState: .unknown) }
         snapshot.appendItems(items, toSection: .statuses)
+        let crumb = Breadcrumb(level: .info, category: "TimelineViewController")
+        crumb.message = "Restoring statuses"
+        crumb.data = [
+            "statusIDs": position.statusIDs
+        ]
+        SentrySDK.addBreadcrumb(crumb: crumb)
         dataSource.apply(snapshot, animatingDifferences: false) {
             if let centerStatusID,
                let index = statusIDs.firstIndex(of: centerStatusID),
@@ -426,7 +460,12 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
     
     private func filterResult(state: FilterState, statusID: String) -> (Filterer.Result, NSAttributedString?) {
         let status = {
-            let status = self.mastodonController.persistentContainer.status(for: statusID)!
+            guard let status = self.mastodonController.persistentContainer.status(for: statusID) else {
+                let crumb = Breadcrumb(level: .fatal, category: "TimelineViewController")
+                crumb.message = "Looking up status \(statusID)"
+                SentrySDK.addBreadcrumb(crumb: crumb)
+                preconditionFailure("Missing status for filtering")
+            }
             // if the status is a reblog of another one, filter based on that one
             if let reblogged = status.reblog {
                 return (reblogged, true)