Add ModelStorage.fetchID()

Author: colemancda

Sources/CoreDataModel/NSEntityDescription.swift

@@ -30,6 +30,7 @@ internal extension NSEntityDescription {
         properties += entity.attributes.map { NSAttributeDescription(attribute: $0) }
         properties += entity.relationships.map { NSRelationshipDescription(relationship: $0) }
         self.properties = properties
+        self.uniquenessConstraints = [[NSManagedObject.BuiltInProperty.id.rawValue as NSString]]
     }
 }
 

Sources/CoreDataModel/NSFetchRequest.swift

@@ -14,8 +14,12 @@ import CoreModel
 public extension FetchRequest {
 
     func toFoundation() -> NSFetchRequest<NSManagedObject> {
+        toFoundation(NSManagedObject.self)
+    }
+    
+    func toFoundation<ResultType: NSFetchRequestResult>(_ result: ResultType.Type) -> NSFetchRequest<ResultType> {
 
-        let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: entity.rawValue)
+        let fetchRequest = NSFetchRequest<ResultType>(entityName: entity.rawValue)
         fetchRequest.predicate = predicate?.toFoundation()
         fetchRequest.fetchLimit = fetchLimit
         fetchRequest.sortDescriptors = sortDescriptors.map {

Sources/CoreDataModel/NSManagedObjectContext.swift

@@ -49,6 +49,13 @@ extension NSManagedObjectContext: ModelStorage {
         }
         self.delete(managedObject)
     }
+    
+    public func fetchID(_ fetchRequest: FetchRequest) throws -> [ObjectID] {
+        let fetch = fetchRequest.toFoundation()
+        fetch.propertiesToFetch = [NSManagedObject.BuiltInProperty.id.rawValue]
+        fetch.returnsObjectsAsFaults = false
+        return try self.fetch(fetchRequest.toFoundation()).map { try $0.modelObjectID }
+    }
 }
 
 internal extension NSManagedObjectContext {

Sources/CoreDataModel/NSPersistentContainer.swift

@@ -50,6 +50,12 @@ extension NSPersistentContainer: ModelStorage {
             try context.delete(entity, for: id)
         }
     }
+    
+    public func fetchID(_ fetchRequest: FetchRequest) async throws -> [ObjectID] {
+        try await performBackgroundTask { context in
+            try context.fetchID(fetchRequest)
+        }
+    }
 }
 
 @available(macOS 12, iOS 15, watchOS 8, tvOS 15, *)

Sources/CoreModel/Store.swift

@@ -15,6 +15,9 @@ public protocol ModelStorage {
     /// Fetch managed objects.
     func fetch(_ fetchRequest: FetchRequest) async throws -> [ModelData]
 
+    /// Fetch managed objects IDs.
+    func fetchID(_ fetchRequest: FetchRequest) async throws -> [ObjectID]
+    
     /// Fetch and return result count.
     func count(_ fetchRequest: FetchRequest) async throws -> UInt