Bugfix FXIOS-9998 [inactive tabs] Fix crash when deleting and the undoing the inactive tabs multiple times in a row (related improvements FXIOS-9954, FXIOS-10010, FXIOS-9999)

firefox-ios/Client.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -140,8 +140,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-crypto.git",
       "state" : {
-        "revision" : "9f95b4d033a4edd3814b48608db3f2ca90c7218b",
-        "version" : "3.7.0"
+        "revision" : "81bee98e706aee68d39ed5996db069ef2b313d62",
+        "version" : "3.7.1"
       }
     },
     {

firefox-ios/Client/Frontend/Browser/Tabs/Legacy/LegacyInactiveTabs/LegacyInactiveTabViewModel.swift

@@ -48,19 +48,6 @@ class LegacyInactiveTabViewModel {
         updateFilteredTabs()
     }
 
-    // FIXME What is this comment saying? I don't have context... the dates described are wrong, and it didn't use the
-    // debug test wrapper like the 2 other places this logic was used.
-    //
-    /// This function returns any tabs that are less than four days old.
-    ///
-    /// Because the "Jump Back In" and "Inactive Tabs" features are separate features,
-    /// it is not a given that a tab has an active/inactive state. Thus, we must
-    /// assume that if we want to use active/inactive state, we can do so without
-    /// that particular feature being active but still respecting that logic.
-    static func getActiveEligibleTabsFrom(_ tabs: [Tab]) -> [Tab] {
-        return tabs.filter({ $0.isActive })
-    }
-
     // MARK: - Private functions
     private func updateModelState(state: TabUpdateState) {
         let hasRunInactiveTabFeatureBefore = LegacyInactiveTabModel.hasRunInactiveTabFeatureBefore

firefox-ios/Client/Frontend/Browser/Tabs/Middleware/TabManagerMiddleware.swift

@@ -233,7 +233,7 @@ class TabManagerMiddleware {
 
         let tabManager = tabManager(for: uuid)
         var inactiveTabs = [InactiveTabsModel]()
-        for tab in tabManager.getInactiveTabs() {
+        for tab in tabManager.inactiveTabs {
             let inactiveTab = InactiveTabsModel(tabUUID: tab.tabUUID,
                                                 title: tab.displayTitle,
                                                 url: tab.url,
@@ -305,10 +305,13 @@ class TabManagerMiddleware {
     /// - Returns: If is the last tab to be closed used to trigger dismissTabTray action
     private func closeTab(with tabUUID: TabUUID, uuid: WindowUUID, isPrivate: Bool) async -> Bool {
         let tabManager = tabManager(for: uuid)
+        // In non-private mode, if:
+        //      A) the last normal active tab is closed, or
+        //      B) the last of ALL normal tabs are closed (i.e. all tabs are inactive and closed at once),
+        // then we want to close the tray.
         let isLastActiveTab = isPrivate
                             ? tabManager.privateTabs.count == 1
-                            : tabManager.normalActiveTabs.count == 1
-
+                            : (tabManager.normalActiveTabs.count <= 1 || tabManager.normalTabs.count == 1)
         await tabManager.removeTab(tabUUID)
         return isLastActiveTab
     }
@@ -424,8 +427,8 @@ class TabManagerMiddleware {
 
     // MARK: - Inactive tabs helper
 
-    /// Close all inactive tabs removing them from the tabs array on `TabManager`.
-    /// Makes a backup of tabs to be deleted in case undo option is selected
+    /// Close all inactive tabs, removing them from the tabs array on `TabManager`.
+    /// Makes a backup of tabs to be deleted in case the undo option is selected.
     private func closeAllInactiveTabs(state: AppState, uuid: WindowUUID) {
         guard let tabsState = state.screenState(TabsPanelState.self, for: .tabsPanel, window: uuid) else { return }
         let tabManager = tabManager(for: uuid)
@@ -436,6 +439,14 @@ class TabManagerMiddleware {
                                                          actionType: TabPanelMiddlewareActionType.refreshInactiveTabs)
             store.dispatch(refreshAction)
 
+            // Refresh the active tabs panel. Can only happen if the user is in normal browsering mode (not private).
+            // Related: FXIOS-10010, FXIOS-9954, FXIOS-9999
+            let model = getTabsDisplayModel(for: false, shouldScrollToTab: false, uuid: uuid)
+            let refreshActiveTabsPanelAction = TabPanelMiddlewareAction(tabDisplayModel: model,
+                                                                        windowUUID: uuid,
+                                                                        actionType: TabPanelMiddlewareActionType.refreshTabs)
+            store.dispatch(refreshActiveTabsPanelAction)
+
             let inactiveTabsCount = tabsState.inactiveTabs.count
             let toastAction = TabPanelMiddlewareAction(toastType: .closedAllInactiveTabs(count: inactiveTabsCount),
                                                        windowUUID: uuid,

firefox-ios/Client/TabManagement/Legacy/LegacyTabManager.swift

@@ -87,7 +87,7 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
     }
 
     var normalActiveTabs: [Tab] {
-        return LegacyInactiveTabViewModel.getActiveEligibleTabsFrom(normalTabs)
+        return normalTabs.filter({ $0.isActive })
     }
 
     var inactiveTabs: [Tab] {
@@ -98,10 +98,9 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         return tabs.filter { $0.isPrivate }
     }
 
-    /// This variable returns all normal tabs, sorted chronologically, excluding any
-    /// home page tabs.
+    /// This variable returns all normal tabs, sorted chronologically, excluding any home page tabs.
     var recentlyAccessedNormalTabs: [Tab] {
-        var eligibleTabs = viableTabs()
+        var eligibleTabs = normalActiveTabs // Do not include inactive tabs, as they are not "recently" accessed
 
         eligibleTabs = eligibleTabs.filter { tab in
             if tab.lastKnownUrl == nil {
@@ -132,6 +131,15 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         return tabs[_selectedIndex]
     }
 
+    var selectedTabUUID: UUID? {
+        guard let selectedTab = self.selectedTab,
+              let uuid = UUID(uuidString: selectedTab.tabUUID) else {
+            return nil
+        }
+
+        return uuid
+    }
+
     subscript(index: Int) -> Tab? {
         if index >= tabs.count {
             return nil
@@ -413,6 +421,7 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         return popup
     }
 
+    /// Note: Inserts AND configures the given tab.
     func configureTab(_ tab: Tab,
                       request: URLRequest?,
                       afterTab parent: Tab? = nil,
@@ -546,12 +555,9 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
     // MARK: - Remove tabs
     func removeTab(_ tab: Tab, completion: (() -> Void)? = nil) {
         guard let index = tabs.firstIndex(where: { $0 === tab }) else { return }
-        DispatchQueue.main.async { [unowned self] in
-            // gather the index of the deleted tab within the viable tabs array
-            // so we can select the correct next tab after deletion
-            let viableTabsIndex = deletedIndexForViableTabs(tab)
-            self.removeTab(tab, flushToDisk: true)
-            self.updateIndexAfterRemovalOf(tab, deletedIndex: index, viableTabsIndex: viableTabsIndex)
+        DispatchQueue.main.async { [weak self] in
+            self?.removeTab(tab, flushToDisk: true)
+            self?.updateSelectedTabAfterRemovalOf(tab, deletedIndex: index)
             completion?()
         }
 
@@ -568,15 +574,14 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         guard let index = tabs.firstIndex(where: { $0.tabUUID == tabUUID }) else { return }
 
         let tab = tabs[index]
-        let viableTabsIndex = deletedIndexForViableTabs(tab)
         if TabTrayFlagManager.isRefactorEnabled {
             backupCloseTab = BackupCloseTab(
                 tab: tab,
-                restorePosition: viableTabsIndex,
+                restorePosition: index,
                 isSelected: selectedTab?.tabUUID == tab.tabUUID)
         }
         self.removeTab(tab, flushToDisk: true)
-        self.updateIndexAfterRemovalOf(tab, deletedIndex: index, viableTabsIndex: viableTabsIndex)
+        self.updateSelectedTabAfterRemovalOf(tab, deletedIndex: index) // Crash path
 
         TelemetryWrapper.recordEvent(
             category: .action,
@@ -819,56 +824,96 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         privateConfiguration.preferences.javaScriptCanOpenWindowsAutomatically = allowPopups
     }
 
-    // returns all activate tabs (private or normal)
-    private func viableTabs(isPrivate: Bool = false) -> [Tab] {
-        if !isPrivate, featureFlags.isFeatureEnabled(.inactiveTabs, checking: .buildAndUser) {
-            // only use active tabs as viable tabs
-            // we cannot use recentlyAccessedNormalTabs as this is filtering for sponsored and sorting tabs
-            return LegacyInactiveTabViewModel.getActiveEligibleTabsFrom(normalTabs)
-        } else {
-            return isPrivate ? privateTabs : normalTabs
+    private func updateSelectedTabAfterRemovalOf(_ removedTab: Tab, deletedIndex: Int) {
+        // We have to handle 3 different types of tabs: private tabs, normal active tabs, and normal inactive tabs.
+        // These tabs are all in the `tabs` array but are differentiated by their respective flags.
+        //
+        // Once a tab has been removed, we must consider several situations:
+        // A) A change in the `tabs` array size, which may require us to shift the selected tab index 1 to the left
+        // B) If the removed tab was selected, we must choose an appropriate next selected tab from among the existing tabs
+        // C) When we close the last tab of a certain type, we may need to perform additional logic
+        //      - For example, closing the last private tab should select the most recent active normal tab, if possible
+
+        // Viable tabs for selection are private tabs and normal active tabs. We never want to select a normal inactive tab.
+        let viableTabsToSelect = removedTab.isPrivate
+                          ? privateTabs
+                          : normalActiveTabs
+
+        // When the user closes the last private tab or last normal active tab, we must handle this gracefully.
+        guard !viableTabsToSelect.isEmpty else {
+            if removedTab.isPrivate,
+               let mostRecentActiveTab = mostRecentTab(inTabs: normalActiveTabs) {
+                selectTab(mostRecentActiveTab, previous: removedTab)
+            } else {
+                selectTab(addTab(), previous: removedTab)
+            }
+            return
         }
-    }
 
-    // returns the index of a deleted tab in the viable tabs array
-    private func deletedIndexForViableTabs(_ tab: Tab) -> Int {
-        let viableTabs = viableTabs(isPrivate: tab.isPrivate)
-        return viableTabs.firstIndex(of: tab) ?? -1
-    }
-
-    private func updateIndexAfterRemovalOf(_ tab: Tab, deletedIndex: Int, viableTabsIndex: Int) {
-        let closedLastNormalActiveTab = !tab.isPrivate && normalActiveTabs.isEmpty
-        let closedLastPrivateTab = tab.isPrivate && privateTabs.isEmpty
-
-        if closedLastNormalActiveTab {
-            // When we close the last normal tab (or last active normal tab), we should show the Home screen.
-            selectTab(addTab(), previous: tab)
-        } else if closedLastPrivateTab {
-            selectTab(mostRecentTab(inTabs: tabs) ?? tabs.last, previous: tab)
-        } else if deletedIndex == _selectedIndex {
-            if !selectParentTab(afterRemoving: tab) {
-                // We only consider active tabs viable (we don't want to surface a 2 week old inactive tab)
-                let viableTabs = viableTabs(isPrivate: tab.isPrivate)
-                let activeViableTabs = LegacyInactiveTabViewModel.getActiveEligibleTabsFrom(viableTabs)
-
-                // Try to select the active tab to the left or right of the removed tab. If that fails, fallback to
-                // selecting the most recent tab
-                if let rightOrLeftTab =
-                    activeViableTabs[safe: viableTabsIndex] ?? activeViableTabs[safe: viableTabsIndex - 1] {
-                    selectTab(rightOrLeftTab, previous: tab)
-                } else {
-                    let mostRecentTab = mostRecentTab(inTabs: activeViableTabs) ?? activeViableTabs.last
-                    selectTab(mostRecentTab, previous: tab)
-                }
+        // When the currently selected tab has been deleted, try to select the next most reasonable tab. However, we must
+        // never surface an old inactive tab.
+        if deletedIndex == _selectedIndex {
+            let mostRecentViableTab = mostRecentTab(inTabs: viableTabsToSelect)
+
+            if let mostRecentViableTab, mostRecentViableTab == removedTab.parent {
+                // 1. Try to select the most recently used viable tab, if it's the removed tab's parent.
+                selectTab(mostRecentViableTab, previous: removedTab)
+            } else if !removedTab.isNormalAndInactive,
+                      let rightOrLeftTab = findRightOrLeftTab(forRemovedTab: removedTab, withDeletedIndex: deletedIndex) {
+                // 2. Try to select an array neighbour of the same tab type, except if the removed tab is inactive (unlikely
+                // edge case).
+                selectTab(rightOrLeftTab, previous: removedTab)
+            } else {
+                // 3. If there are no suitable active tabs to select, create a new normal active tab.
+                // (Note: It's possible to fall into here when all tabs have become inactive, especially when debugging.)
+                selectTab(addTab(), previous: removedTab)
             }
         } else if deletedIndex < _selectedIndex {
-            // If we delete an active tab that's before the selected active tab, we need to shift our selection index
-            // since the array size has changed.
-            let selected = tabs[safe: _selectedIndex - 1]
-            selectTab(selected, previous: selected)
+            // If we delete a tab in the `tabs` array that's earlier than the selected tab, we need to shift our index.
+            // The selected tab itself hasn't actually changed. Reselect it to call code paths related to saving, etc.
+            if let selectedTab = tabs[safe: _selectedIndex - 1] {
+                selectTab(selectedTab, previous: selectedTab)
+            } else {
+                assertionFailure("This should never happen!")
+                selectTab(addTab())
+            }
         }
     }
 
+    /// Returns a direct neighbouring tab of the same type as the removed tab.
+    /// - Parameters:
+    ///   - removedTab: A tab that was just removed from the `tabs` array.
+    ///   - deletedIndex: The former index of the removed tab in the `tabs` array.
+    /// - Returns: Returns the neighbouring tab of the same type as removedTab. Preference given to the tab on the right.
+    func findRightOrLeftTab(forRemovedTab removedTab: Tab, withDeletedIndex deletedIndex: Int) -> Tab? {
+        // We know the fomer index of the removed tab in the full `tabs` array. However, if we want to get the closest
+        // neighbouring tab of the same type, we need to map this index into a subarray containing only tabs of that type.
+        //
+        // Example:
+        //          An array with private tabs (P), inactive normal tabs (I), and active normal tabs (A) is as follows. The
+        //          deleted index is 7, indicating normal active tab A3 was previously removed.
+        //          [P1, P2, A1, I1, A2, I2, P3, A3, A4, P4]
+        //                                       ^ deletedIndex is 7
+        //
+        //          We can map this deletedIndex to an index into a filtered subarray containing only normal active tabs.
+        //          To do this, we count the number of normal active tabs in the `tabs` array in the range 0..<deletedIndex.
+        //          In this case, there are two: A1 and A2.
+        //
+        //          [A1, A2, _, A4]
+        //                   ^ deletedIndex mapped to subarray of normal active tabs is 2
+        //
+        let arraySlice = tabs[0..<deletedIndex]
+
+        // Get the count of similar tabs on left side of the array
+        let mappedDeletedIndex = arraySlice.filter({ removedTab.isSameTypeAs($0) }).count
+        let filteredTabs = tabs.filter({ removedTab.isSameTypeAs($0) })
+
+        // Now that we know at which index in the subarray the removedTab was removed, we can look for its nearest left or
+        // right neighbours of the same type. This code checks the right tab first, then the left tab.
+        // Note: Use safe index into arrays to protect against out of bounds errors (e.g. deletedIndex is 0).
+        return filteredTabs[safe: mappedDeletedIndex] ?? filteredTabs[safe: mappedDeletedIndex - 1]
+    }
+
     private func reAddTabs(tabsToAdd: [Tab], previousTabUUID: TabUUID, isPrivate: Bool = false) {
         tabs.append(contentsOf: tabsToAdd)
         let tabToSelect = tabs.first(where: { $0.tabUUID == previousTabUUID })
@@ -905,24 +950,6 @@ class LegacyTabManager: NSObject, FeatureFlaggable, TabManager, TabEventHandler
         storeChanges()
     }
 
-    // Select the most recently visited tab, IFF it is also the parent tab of the closed tab.
-    private func selectParentTab(afterRemoving tab: Tab) -> Bool {
-        let viableTabs = (tab.isPrivate ? privateTabs : normalTabs).filter { $0 != tab }
-        guard let parentTab = tab.parent,
-              parentTab != tab,
-              !viableTabs.isEmpty,
-              viableTabs.contains(parentTab)
-        else { return false }
-
-        let parentTabIsMostRecentUsed = mostRecentTab(inTabs: viableTabs) == parentTab
-
-        if parentTabIsMostRecentUsed {
-            selectTab(parentTab, previous: tab)
-            return true
-        }
-        return false
-    }
-
     // MARK: - Start at Home
 
     /// Public interface for checking whether the StartAtHome Feature should run.

firefox-ios/Client/TabManagement/Tab.swift

@@ -80,6 +80,18 @@ class Tab: NSObject, ThemeApplicable {
         }
     }
 
+    var isNormal: Bool {
+        return !isPrivate
+    }
+
+    var isNormalActive: Bool {
+        return !isPrivate && isActive
+    }
+
+    var isNormalAndInactive: Bool {
+        return !isPrivate && isInactive
+    }
+
     /// The window associated with the tab (where the tab lives and will be displayed).
     /// Currently tabs cannot be actively moved between windows on iPadOS, however this
     /// may change in the future.
@@ -888,6 +900,14 @@ class Tab: NSObject, ThemeApplicable {
     func applyTheme(theme: Theme) {
         UITextField.appearance().keyboardAppearance = theme.type.keyboardAppearence(isPrivate: isPrivate)
     }
+
+    // MARK: - Static Helpers
+
+    /// Returns true if the tabs both have the same type of private, normal active, and normal inactive.
+    /// Simply checks the `isPrivate` and `isActive` flags of both tabs.
+    func isSameTypeAs(_ otherTab: Tab) -> Bool {
+        return isPrivate == otherTab.isPrivate && isActive == otherTab.isActive
+    }
 }
 
 extension Tab: UIGestureRecognizerDelegate {

firefox-ios/Client/TabManagement/TabManager.swift

@@ -21,9 +21,10 @@ protocol TabManager: AnyObject {
     var tabs: [Tab] { get }
     var count: Int { get }
     var selectedTab: Tab? { get }
+    var selectedTabUUID: UUID? { get }
     var backupCloseTab: BackupCloseTab? { get set }
     var backupCloseTabs: [Tab] { get set }
-    var normalTabs: [Tab] { get }
+    var normalTabs: [Tab] { get } // Includes active and inactive tabs
     var normalActiveTabs: [Tab] { get }
     var inactiveTabs: [Tab] { get }
     var privateTabs: [Tab] { get }
@@ -59,6 +60,7 @@ protocol TabManager: AnyObject {
                                          isPrivate: Bool,
                                          previousTabUUID: TabUUID)
     func undoCloseAllTabsLegacy(recentlyClosedTabs: [Tab], previousTabUUID: TabUUID, isPrivate: Bool)
+    func findRightOrLeftTab(forRemovedTab removedTab: Tab, withDeletedIndex deletedIndex: Int) -> Tab?
 
     @discardableResult
     func addTab(_ request: URLRequest!,