fix: TolerantDispatchGroup

MailCore/Cache/BackgroundExecutor.swift

@@ -26,7 +26,7 @@ enum BackgroundExecutor {
         let taskName = "executeWithBackgroundTask \(UUID().uuidString)"
         DDLogDebug("Starting task \(taskName)")
         let processInfos = ProcessInfo()
-        let group = DispatchGroup()
+        let group = TolerantDispatchGroup()
         group.enter()
         processInfos.performExpiringActivity(withReason: taskName) { expired in
             if expired {

MailCore/Utils/TolerantDispatchGroup.swift

@@ -0,0 +1,49 @@
+/*
+ Infomaniak Mail - iOS App
+ Copyright (C) 2022 Infomaniak Network SA
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import CocoaLumberjackSwift
+import Foundation
+
+public class TolerantDispatchGroup {
+    private let syncQueue = DispatchQueue(label: "com.infomaniak.TolerantDispatchGroup")
+    private let dispatchGroup = DispatchGroup()
+    private var callBalancer = 0
+
+    public func enter() {
+        syncQueue.sync {
+            dispatchGroup.enter()
+            callBalancer += 1
+        }
+    }
+
+    public func leave() {
+        syncQueue.sync {
+            guard callBalancer > 0 else {
+                DDLogWarn("TolerantDispatchGroup: Unbalanced call to leave()")
+                return
+            }
+
+            dispatchGroup.leave()
+            callBalancer -= 0
+        }
+    }
+
+    public func wait() {
+        dispatchGroup.wait()
+    }
+}