Fixed a number of crashes

Consolidated the PagedDatabaseObserver updating logic into a static function (can be improved further in the future)
Added defensive coding to prevent the LinkDeviceVC from crashing when the nav controller doesn't exist
Fixed an issue where the 'Permissions' callbacks were doing UI logic on background threads
Fixed an issue where the 'reloadCurrent' load type for the PagedDatabaseObserver was incorrectly increasing the 'currentCount' of the PageInfo
Fixed an issue where loading all of the data for paged data could result in a crash when the 'loadMore' section was removed

Podfile

@@ -82,6 +82,7 @@ abstract_target 'GlobalDependencies' do
       target 'SessionUtilitiesKit' do
         pod 'SAMKeychain'
         pod 'YYImage/libwebp', git: 'https://github.com/signalapp/YYImage'
+        pod 'DifferenceKit'
         
         target 'SessionUtilitiesKitTests' do
           inherit! :complete

Podfile.lock

@@ -21,11 +21,11 @@ PODS:
   - Curve25519Kit (2.1.0):
     - CocoaLumberjack
     - SignalCoreKit
-  - DifferenceKit (1.2.0):
-    - DifferenceKit/Core (= 1.2.0)
-    - DifferenceKit/UIKitExtension (= 1.2.0)
-  - DifferenceKit/Core (1.2.0)
-  - DifferenceKit/UIKitExtension (1.2.0):
+  - DifferenceKit (1.3.0):
+    - DifferenceKit/Core (= 1.3.0)
+    - DifferenceKit/UIKitExtension (= 1.3.0)
+  - DifferenceKit/Core (1.3.0)
+  - DifferenceKit/UIKitExtension (1.3.0):
     - DifferenceKit/Core
   - GRDB.swift/SQLCipher (6.1.0):
     - SQLCipher (>= 3.4.2)
@@ -221,7 +221,7 @@ SPEC CHECKSUMS:
   CocoaLumberjack: 543c79c114dadc3b1aba95641d8738b06b05b646
   CryptoSwift: a532e74ed010f8c95f611d00b8bbae42e9fe7c17
   Curve25519Kit: e63f9859ede02438ae3defc5e1a87e09d1ec7ee6
-  DifferenceKit: 5659c430bb7fe45876fa32ce5cba5d6167f0c805
+  DifferenceKit: ab185c4d7f9cef8af3fcf593e5b387fb81e999ca
   GRDB.swift: 611778a5e113385373baeb3e2ce474887d1aadb7
   libwebp: 98a37e597e40bfdb4c911fc98f2c53d0b12d05fc
   Nimble: 5316ef81a170ce87baf72dd961f22f89a602ff84
@@ -242,6 +242,6 @@ SPEC CHECKSUMS:
   YYImage: f1ddd15ac032a58b78bbed1e012b50302d318331
   ZXingObjC: fdbb269f25dd2032da343e06f10224d62f537bdb
 
-PODFILE CHECKSUM: 402850f74d70b3b57fc81eff82d0fc86d695b392
+PODFILE CHECKSUM: 7452ce88370eadd58d21fdf6a4c4945d6554ee95
 
 COCOAPODS: 1.11.3

Session/Conversations/ConversationVC+Interaction.swift

@@ -2019,7 +2019,9 @@ extension ConversationVC:
     func startVoiceMessageRecording() {
         // Request permission if needed
         Permissions.requestMicrophonePermissionIfNeeded() { [weak self] in
-            self?.cancelVoiceMessageRecording()
+            DispatchQueue.main.async {
+                self?.cancelVoiceMessageRecording()
+            }
         }
         
         // Keep screen on

Session/Conversations/ConversationVC.swift

@@ -1,6 +1,7 @@
 // Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.
 
 import UIKit
+import AVKit
 import GRDB
 import DifferenceKit
 import SessionUIKit

Session/Conversations/ConversationViewModel.swift

@@ -247,32 +247,14 @@ public class ConversationViewModel: OWSAudioPlayerDelegate {
                 )
             ],
             onChangeUnsorted: { [weak self] updatedData, updatedPageInfo in
-                guard
-                    let currentData: [SectionModel] = self?.interactionData,
-                    let updatedInteractionData: [SectionModel] = self?.process(data: updatedData, for: updatedPageInfo)
-                else { return }
-                
-                let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-                    source: currentData,
-                    target: updatedInteractionData
-                )
-                
-                // No need to do anything if there were no changes
-                guard !changeset.isEmpty else { return }
-                
-                // Run any changes on the main thread (as they will generally trigger UI updates)
-                DispatchQueue.main.async {
-                    // If we have the callback then trigger it, otherwise just store the changes to be sent
-                    // to the callback if we ever start observing again (when we have the callback it needs
-                    // to do the data updating as it's tied to UI updates and can cause crashes if not updated
-                    // in the correct order)
-                    guard let onInteractionChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self?.onInteractionChange else {
-                        self?.unobservedInteractionDataChanges = (updatedInteractionData, changeset)
-                        return
+                PagedData.processAndTriggerUpdates(
+                    updatedData: self?.process(data: updatedData, for: updatedPageInfo),
+                    currentDataRetriever: { self?.interactionData },
+                    onDataChange: self?.onInteractionChange,
+                    onUnobservedDataChange: { updatedData, changeset in
+                        self?.unobservedInteractionDataChanges = (updatedData, changeset)
                     }
-                    
-                    onInteractionChange(updatedInteractionData, changeset)
-                }
+                )
             }
         )
     }

Session/Home/HomeViewModel.swift

@@ -150,42 +150,14 @@ public class HomeViewModel {
                 orderSQL: SessionThreadViewModel.homeOrderSQL
             ),
             onChangeUnsorted: { [weak self] updatedData, updatedPageInfo in
-                guard
-                    let currentData: [SectionModel] = self?.threadData,
-                    let updatedThreadData: [SectionModel] = self?.process(data: updatedData, for: updatedPageInfo)
-                else { return }
-                
-                let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-                    source: currentData,
-                    target: updatedThreadData
-                )
-                
-                // No need to do anything if there were no changes
-                guard !changeset.isEmpty else { return }
-                
-                let performUpdates = {
-                    // If we have the callback then trigger it, otherwise just store the changes to be sent
-                    // to the callback if we ever start observing again (when we have the callback it needs
-                    // to do the data updating as it's tied to UI updates and can cause crashes if not updated
-                    // in the correct order)
-                    guard let onThreadChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self?.onThreadChange else {
-                        self?.unobservedThreadDataChanges = (updatedThreadData, changeset)
-                        return
+                PagedData.processAndTriggerUpdates(
+                    updatedData: self?.process(data: updatedData, for: updatedPageInfo),
+                    currentDataRetriever: { self?.threadData },
+                    onDataChange: self?.onThreadChange,
+                    onUnobservedDataChange: { updatedData, changeset in
+                        self?.unobservedThreadDataChanges = (updatedData, changeset)
                     }
-                    
-                    onThreadChange(updatedThreadData, changeset)
-                }
-                
-                // Note: On the initial launch the data will be fetched on the main thread and we want it
-                // to block so don't dispatch to the next run loop
-                guard !Thread.isMainThread else {
-                    return performUpdates()
-                }
-                
-                // Run any changes on the main thread (as they will generally trigger UI updates)
-                DispatchQueue.main.async {
-                    performUpdates()
-                }
+                )
             }
         )
         
@@ -246,20 +218,15 @@ public class HomeViewModel {
             data: currentData.flatMap { $0.elements },
             for: currentPageInfo
         )
-        let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-            source: currentData,
-            target: updatedThreadData
+        
+        PagedData.processAndTriggerUpdates(
+            updatedData: updatedThreadData,
+            currentDataRetriever: { [weak self] in (self?.unobservedThreadDataChanges?.0 ?? self?.threadData) },
+            onDataChange: onThreadChange,
+            onUnobservedDataChange: { [weak self] updatedThreadData, changeset in
+                self?.unobservedThreadDataChanges = (updatedThreadData, changeset)
+            }
         )
-        
-        // No need to do anything if there were no changes
-        guard !changeset.isEmpty else { return }
-        
-        guard let onThreadChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self.onThreadChange else {
-            self.unobservedThreadDataChanges = (updatedThreadData, changeset)
-            return
-        }
-        
-        onThreadChange(updatedThreadData, changeset)
     }
     
     // MARK: - Thread Data

Session/Home/Message Requests/MessageRequestsViewModel.swift

@@ -98,32 +98,14 @@ public class MessageRequestsViewModel {
                 orderSQL: SessionThreadViewModel.messageRequetsOrderSQL
             ),
             onChangeUnsorted: { [weak self] updatedData, updatedPageInfo in
-                guard
-                    let currentData: [SectionModel] = self?.threadData,
-                    let updatedThreadData: [SectionModel] = self?.process(data: updatedData, for: updatedPageInfo)
-                else { return }
-                
-                let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-                    source: currentData,
-                    target: updatedThreadData
-                )
-                
-                // No need to do anything if there were no changes
-                guard !changeset.isEmpty else { return }
-                
-                // Run any changes on the main thread (as they will generally trigger UI updates)
-                DispatchQueue.main.async {
-                    // If we have the callback then trigger it, otherwise just store the changes to be sent
-                    // to the callback if we ever start observing again (when we have the callback it needs
-                    // to do the data updating as it's tied to UI updates and can cause crashes if not updated
-                    // in the correct order)
-                    guard let onThreadChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self?.onThreadChange else {
-                        self?.unobservedThreadDataChanges = (updatedThreadData, changeset)
-                        return
+                PagedData.processAndTriggerUpdates(
+                    updatedData: self?.process(data: updatedData, for: updatedPageInfo),
+                    currentDataRetriever: { self?.threadData },
+                    onDataChange: self?.onThreadChange,
+                    onUnobservedDataChange: { updatedData, changeset in
+                        self?.unobservedThreadDataChanges = (updatedData, changeset)
                     }
-                    
-                    onThreadChange(updatedThreadData, changeset)
-                }
+                )
             }
         )
         

Session/Home/New Conversation/NewDMVC.swift

@@ -131,8 +131,10 @@ final class NewDMVC: BaseVC, UIPageViewControllerDataSource, UIPageViewControlle
     }
     
     fileprivate func handleCameraAccessGranted() {
-        pages[1] = scanQRCodeWrapperVC
-        pageVC.setViewControllers([ scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        DispatchQueue.main.async {
+            self.pages[1] = self.scanQRCodeWrapperVC
+            self.pageVC.setViewControllers([ self.scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        }
     }
     
     // MARK: - Updating

Session/Media Viewing & Editing/MediaGalleryViewModel.swift

@@ -93,32 +93,14 @@ public class MediaGalleryViewModel {
             orderSQL: Item.galleryOrderSQL,
             dataQuery: Item.baseQuery(orderSQL: Item.galleryOrderSQL),
             onChangeUnsorted: { [weak self] updatedData, updatedPageInfo in
-                guard
-                    let currentData: [SectionModel] = self?.galleryData,
-                    let updatedGalleryData: [SectionModel] = self?.process(data: updatedData, for: updatedPageInfo)
-                else { return }
-                
-                let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-                    source: currentData,
-                    target: updatedGalleryData
-                )
-                
-                // No need to do anything if there were no changes
-                guard !changeset.isEmpty else { return }
-                
-                // Run any changes on the main thread (as they will generally trigger UI updates)
-                DispatchQueue.main.async {
-                    // If we have the callback then trigger it, otherwise just store the changes to be sent
-                    // to the callback if we ever start observing again (when we have the callback it needs
-                    // to do the data updating as it's tied to UI updates and can cause crashes if not updated
-                    // in the correct order)
-                    guard let onGalleryChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self?.onGalleryChange else {
-                        self?.unobservedGalleryDataChanges = (updatedGalleryData, changeset)
-                        return
+                PagedData.processAndTriggerUpdates(
+                    updatedData: self?.process(data: updatedData, for: updatedPageInfo),
+                    currentDataRetriever: { self?.galleryData },
+                    onDataChange: self?.onGalleryChange,
+                    onUnobservedDataChange: { updatedData, changeset in
+                        self?.unobservedGalleryDataChanges = (updatedData, changeset)
                     }
-                    
-                    onGalleryChange(updatedGalleryData, changeset)
-                }
+                )
             }
         )
         

Session/Media Viewing & Editing/SendMediaNavigationController.swift

@@ -142,13 +142,17 @@ class SendMediaNavigationController: UINavigationController {
 
     private func didTapCameraModeButton() {
         Permissions.requestCameraPermissionIfNeeded { [weak self] in
-            self?.fadeTo(viewControllers: ((self?.captureViewController).map { [$0] } ?? []))
+            DispatchQueue.main.async {
+                self?.fadeTo(viewControllers: ((self?.captureViewController).map { [$0] } ?? []))
+            }
         }
     }
 
     private func didTapMediaLibraryModeButton() {
         Permissions.requestLibraryPermissionIfNeeded { [weak self] in
-            self?.fadeTo(viewControllers: ((self?.mediaLibraryViewController).map { [$0] } ?? []))
+            DispatchQueue.main.async {
+                self?.fadeTo(viewControllers: ((self?.mediaLibraryViewController).map { [$0] } ?? []))
+            }
         }
     }
 

Session/Onboarding/LinkDeviceVC.swift

@@ -109,8 +109,10 @@ final class LinkDeviceVC: BaseVC, UIPageViewControllerDataSource, UIPageViewCont
     }
     
     fileprivate func handleCameraAccessGranted() {
-        pages[1] = scanQRCodeWrapperVC
-        pageVC.setViewControllers([ scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        DispatchQueue.main.async {
+            self.pages[1] = self.scanQRCodeWrapperVC
+            self.pageVC.setViewControllers([ self.scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        }
     }
     
     // MARK: - Updating
@@ -161,9 +163,15 @@ final class LinkDeviceVC: BaseVC, UIPageViewControllerDataSource, UIPageViewCont
         GetSnodePoolJob.run()
         
         NotificationCenter.default.addObserver(self, selector: #selector(handleInitialConfigurationMessageReceived), name: .initialConfigurationMessageReceived, object: nil)
-        ModalActivityIndicatorViewController.present(fromViewController: navigationController!) { [weak self] modal in
-            self?.activityIndicatorModal = modal
-        }
+        
+        ModalActivityIndicatorViewController
+            .present(
+                // There was some crashing here due to force-unwrapping so just falling back to
+                // using self if there is no nav controller
+                fromViewController: (self.navigationController ?? self)
+            ) { [weak self] modal in
+                self?.activityIndicatorModal = modal
+            }
     }
     
     @objc private func handleInitialConfigurationMessageReceived(_ notification: Notification) {

Session/Open Groups/JoinOpenGroupVC.swift

@@ -105,8 +105,10 @@ final class JoinOpenGroupVC: BaseVC, UIPageViewControllerDataSource, UIPageViewC
     }
 
     fileprivate func handleCameraAccessGranted() {
-        pages[1] = scanQRCodeWrapperVC
-        pageVC.setViewControllers([ scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        DispatchQueue.main.async {
+            self.pages[1] = self.scanQRCodeWrapperVC
+            self.pageVC.setViewControllers([ self.scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        }
     }
 
     // MARK: - Updating

Session/Settings/BlockedContactsViewModel.swift

@@ -62,32 +62,14 @@ public class BlockedContactsViewModel {
                 orderSQL: DataModel.orderSQL
             ),
             onChangeUnsorted: { [weak self] updatedData, updatedPageInfo in
-                guard
-                    let currentData: [SectionModel] = self?.contactData,
-                    let updatedContactData: [SectionModel] = self?.process(data: updatedData, for: updatedPageInfo)
-                else { return }
-                
-                let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
-                    source: currentData,
-                    target: updatedContactData
-                )
-                
-                // No need to do anything if there were no changes
-                guard !changeset.isEmpty else { return }
-                
-                // Run any changes on the main thread (as they will generally trigger UI updates)
-                DispatchQueue.main.async {
-                    // If we have the callback then trigger it, otherwise just store the changes to be sent
-                    // to the callback if we ever start observing again (when we have the callback it needs
-                    // to do the data updating as it's tied to UI updates and can cause crashes if not updated
-                    // in the correct order)
-                    guard let onContactChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = self?.onContactChange else {
-                        self?.unobservedContactDataChanges = (updatedContactData, changeset)
-                        return
+                PagedData.processAndTriggerUpdates(
+                    updatedData: self?.process(data: updatedData, for: updatedPageInfo),
+                    currentDataRetriever: { self?.contactData },
+                    onDataChange: self?.onContactChange,
+                    onUnobservedDataChange: { updatedData, changeset in
+                        self?.unobservedContactDataChanges = (updatedData, changeset)
                     }
-                    
-                    onContactChange(updatedContactData, changeset)
-                }
+                )
             }
         )
         

Session/Settings/QRCodeVC.swift

@@ -95,8 +95,10 @@ final class QRCodeVC : BaseVC, UIPageViewControllerDataSource, UIPageViewControl
     }
     
     fileprivate func handleCameraAccessGranted() {
-        pages[1] = scanQRCodeWrapperVC
-        pageVC.setViewControllers([ scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        DispatchQueue.main.async {
+            self.pages[1] = self.scanQRCodeWrapperVC
+            self.pageVC.setViewControllers([ self.scanQRCodeWrapperVC ], direction: .forward, animated: false, completion: nil)
+        }
     }
     
     // MARK: - Updating

Session/Settings/SettingsViewModel.swift

@@ -407,12 +407,14 @@ class SettingsViewModel: SessionTableViewModel<SettingsViewModel.NavButton, Sett
     
     private func showPhotoLibraryForAvatar() {
         Permissions.requestLibraryPermissionIfNeeded { [weak self] in
-            let picker: UIImagePickerController = UIImagePickerController()
-            picker.sourceType = .photoLibrary
-            picker.mediaTypes = [ "public.image" ]
-            picker.delegate = self?.imagePickerHandler
-            
-            self?.transitionToScreen(picker, transitionType: .present)
+            DispatchQueue.main.async {
+                let picker: UIImagePickerController = UIImagePickerController()
+                picker.sourceType = .photoLibrary
+                picker.mediaTypes = [ "public.image" ]
+                picker.delegate = self?.imagePickerHandler
+                
+                self?.transitionToScreen(picker, transitionType: .present)
+            }
         }
     }
     

SessionUtilitiesKit/Database/Types/PagedDatabaseObserver.swift

@@ -2,6 +2,7 @@
 
 import Foundation
 import GRDB
+import DifferenceKit
 
 // MARK: - PagedDatabaseObserver
 
@@ -198,6 +199,16 @@ public class PagedDatabaseObserver<ObservedTable, T>: TransactionObserver where
             // Update the cache, pageInfo and the change callback
             self?.dataCache.mutate { $0 = finalUpdatedDataCache }
             self?.pageInfo.mutate { $0 = updatedPageInfo }
+            
+            
+            // Make sure the updates run on the main thread
+            guard Thread.isMainThread else {
+                DispatchQueue.main.async { [weak self] in
+                    self?.onChangeUnsorted(finalUpdatedDataCache.values, updatedPageInfo)
+                }
+                return
+            }
+            
             self?.onChangeUnsorted(finalUpdatedDataCache.values, updatedPageInfo)
         }
         
@@ -673,7 +684,12 @@ public class PagedDatabaseObserver<ObservedTable, T>: TransactionObserver where
             let updatedLimitInfo: PagedData.PageInfo = PagedData.PageInfo(
                 pageSize: currentPageInfo.pageSize,
                 pageOffset: queryInfo.updatedCacheOffset,
-                currentCount: (currentPageInfo.currentCount + newData.count),
+                currentCount: {
+                    switch target {
+                        case .reloadCurrent: return currentPageInfo.currentCount
+                        default: return (currentPageInfo.currentCount + newData.count)
+                    }
+                }(),
                 totalCount: totalCount
             )
             
@@ -726,6 +742,12 @@ public class PagedDatabaseObserver<ObservedTable, T>: TransactionObserver where
             self?.isLoadingMoreData.mutate { $0 = false }
         }
         
+        // Make sure the updates run on the main thread
+        guard Thread.isMainThread else {
+            DispatchQueue.main.async { triggerUpdates() }
+            return
+        }
+        
         triggerUpdates()
     }
     
@@ -996,6 +1018,56 @@ public enum PagedData {
         let rowIndex: Int64
     }
     
+    // MARK: - Convenience Functions
+    
+    // FIXME: Would be good to clean this up further in the future (should be able to do more processing on BG threads)
+    public static func processAndTriggerUpdates<SectionModel: DifferentiableSection>(
+        updatedData: [SectionModel]?,
+        currentDataRetriever: @escaping (() -> [SectionModel]?),
+        onDataChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ())?,
+        onUnobservedDataChange: @escaping (([SectionModel], StagedChangeset<[SectionModel]>) -> Void)
+    ) {
+        guard let updatedData: [SectionModel] = updatedData else { return }
+        
+        // Note: While it would be nice to generate the changeset on a background thread it introduces
+        // a multi-threading issue where a data change can come in while the table is processing multiple
+        // updates resulting in the data being in a partially updated state (which makes the subsequent
+        // table reload crash due to inconsistent state)
+        let performUpdates = {
+            guard let currentData: [SectionModel] = currentDataRetriever() else { return }
+            
+            let changeset: StagedChangeset<[SectionModel]> = StagedChangeset(
+                source: currentData,
+                target: updatedData
+            )
+            
+            // No need to do anything if there were no changes
+            guard !changeset.isEmpty else { return }
+            
+            // If we have the callback then trigger it, otherwise just store the changes to be sent
+            // to the callback if we ever start observing again (when we have the callback it needs
+            // to do the data updating as it's tied to UI updates and can cause crashes if not updated
+            // in the correct order)
+            guard let onDataChange: (([SectionModel], StagedChangeset<[SectionModel]>) -> ()) = onDataChange else {
+                onUnobservedDataChange(updatedData, changeset)
+                return
+            }
+            
+            onDataChange(updatedData, changeset)
+        }
+        
+        // No need to dispatch to the next run loop if we are alread on the main thread
+        guard !Thread.isMainThread else {
+            performUpdates()
+            return
+        }
+        
+        // Run any changes on the main thread (as they will generally trigger UI updates)
+        DispatchQueue.main.async {
+            performUpdates()
+        }
+    }
+    
     // MARK: - Internal Functions
     
     fileprivate static func totalCount(