turns out inout arguments in closures are malloc nightmares. this finally fixes it

CoreStore/Importing Data/BaseDataTransaction+Importing.swift

@@ -86,6 +86,8 @@ public extension BaseDataTransaction {
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            return try autoreleasepool {
+                
                 guard T.shouldInsertFromImportSource(source, inTransaction: self) else {
                     
                     return nil
@@ -95,6 +97,7 @@ public extension BaseDataTransaction {
                 try object.didInsertFromImportSource(source, inTransaction: self)
                 return object
             }
+    }
     
     func importObjects<T where T: NSManagedObject, T: ImportableObject>(
         into: Into<T>,
@@ -105,6 +108,8 @@ public extension BaseDataTransaction {
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            try autoreleasepool {
+                
                 for source in sourceArray {
                     
                     guard T.shouldInsertFromImportSource(source, inTransaction: self) else {
@@ -119,6 +124,7 @@ public extension BaseDataTransaction {
                     }
                 }
             }
+    }
     
     func importObjects<T where T: NSManagedObject, T: ImportableObject>(
         into: Into<T>,
@@ -130,6 +136,8 @@ public extension BaseDataTransaction {
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            try autoreleasepool {
+                
                 var objects = [T]()
                 for source in sourceArray {
                     
@@ -148,6 +156,7 @@ public extension BaseDataTransaction {
                 }
                 postProcess(sorted: objects)
             }
+    }
     
     func importUniqueObject<T where T: NSManagedObject, T: ImportableUniqueObject>(
         into: Into<T>,
@@ -158,6 +167,8 @@ public extension BaseDataTransaction {
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            return try autoreleasepool {
+                
                 let uniqueIDKeyPath = T.uniqueIDKeyPath
                 guard let uniqueIDValue = try T.uniqueIDFromImportSource(source, inTransaction: self) else {
                     
@@ -182,17 +193,20 @@ public extension BaseDataTransaction {
                     return object
                 }
             }
+    }
     
     func importUniqueObjects<T where T: NSManagedObject, T: ImportableUniqueObject>(
         into: Into<T>,
         sourceArray: [T.ImportSource],
-        preProcess: ((inout mapping: [T.UniqueIDType: T.ImportSource]) throws -> Void)? = nil) throws {
+        preProcess: ((mapping: [T.UniqueIDType: T.ImportSource]) throws -> [T.UniqueIDType: T.ImportSource])? = nil) throws {
             
             CoreStore.assert(
                 self.bypassesQueueing || self.transactionQueue.isCurrentExecutionContext(),
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            try autoreleasepool {
+                
                 var mapping = Dictionary<T.UniqueIDType, T.ImportSource>()
                 for source in sourceArray {
                     
@@ -207,18 +221,15 @@ public extension BaseDataTransaction {
                     }
                 }
                 
-            var mappingCopy = mapping // bugfix: prevent deallocation of exhausted items when accessed lazily with .keys and .values
                 if let preProcess = preProcess {
                     
                     try autoreleasepool {
                         
-                    try preProcess(mapping: &mappingCopy)
+                        mapping = try preProcess(mapping: mapping)
                     }
                 }
-            mapping = mappingCopy
                 
-            var mappingCopyForKeys = mapping
+                for object in self.fetchAll(From(T), Where(T.uniqueIDKeyPath, isMemberOf: mapping.keys)) ?? [] {
-            for object in self.fetchAll(From(T), Where(T.uniqueIDKeyPath, isMemberOf: mappingCopyForKeys.keys)) ?? [] {
                     
                     try autoreleasepool {
                         
@@ -249,11 +260,12 @@ public extension BaseDataTransaction {
                     }
                 }
             }
+    }
     
     func importUniqueObjects<T where T: NSManagedObject, T: ImportableUniqueObject>(
         into: Into<T>,
         sourceArray: [T.ImportSource],
-        preProcess: ((inout mapping: [T.UniqueIDType: T.ImportSource]) throws -> Void)? = nil,
+        preProcess: ((mapping: [T.UniqueIDType: T.ImportSource]) throws -> [T.UniqueIDType: T.ImportSource])? = nil,
         postProcess: (sorted: [T]) -> Void) throws {
             
             CoreStore.assert(
@@ -261,6 +273,8 @@ public extension BaseDataTransaction {
                 "Attempted to import an object of type \(typeName(into.entityClass)) outside the transaction's designated queue."
             )
             
+            try autoreleasepool {
+                
                 var sortedIDs = Array<T.UniqueIDType>()
                 var mapping = Dictionary<T.UniqueIDType, T.ImportSource>()
                 for source in sourceArray {
@@ -277,19 +291,16 @@ public extension BaseDataTransaction {
                     }
                 }
                 
-            var mappingCopy = mapping // bugfix: prevent deallocation of exhausted items when accessed lazily with .keys and .values
                 if let preProcess = preProcess {
                     
                     try autoreleasepool {
                         
-                    try preProcess(mapping: &mappingCopy)
+                        mapping = try preProcess(mapping: mapping)
                     }
                 }
-            mapping = mappingCopy
                 
-            var mappingCopyForKeys = mapping
                 var objects = Dictionary<T.UniqueIDType, T>()
-            for object in self.fetchAll(From(T), Where(T.uniqueIDKeyPath, isMemberOf: mappingCopyForKeys.keys)) ?? [] {
+                for object in self.fetchAll(From(T), Where(T.uniqueIDKeyPath, isMemberOf: mapping.keys)) ?? [] {
                     
                     try autoreleasepool {
                         
@@ -326,3 +337,4 @@ public extension BaseDataTransaction {
                 postProcess(sorted: sortedIDs.flatMap { objects[$0] })
             }
     }
+}