Transaction Corruption Fix

Sources/CodableDatastore/Datastore/Datastore.swift

@@ -460,7 +460,7 @@ extension Datastore {
             try await warmupIfNeeded()
 
             return try await persistence._withTransaction(
-                actionName: nil,
+                actionName: "Check Count",
                 options: [.idempotent, .readOnly]
             ) { transaction, _ in
                 let descriptor = try await transaction.datastoreDescriptor(for: self.key)

Sources/CodableDatastore/Persistence/Disk Persistence/Transaction/Transaction.swift

@@ -138,18 +138,20 @@ extension DiskPersistence {
                 deletedPages.removeAll()
             }
 
+            /// If the transaction is read-only, stop here without applying anything to the parent.
+            guard !options.contains(.readOnly) else {
+                assert(entryMutations.isEmpty, "Entries were mutated in a read-only transaction!")
+                assert(createdRootObjects.isEmpty, "Root objects were created in a read-only transaction!")
+                assert(createdIndexes.isEmpty, "Indexes were created in a read-only transaction!")
+                assert(createdPages.isEmpty, "Pages were created in a read-only transaction!")
+                assert(deletedRootObjects.isEmpty, "Root objects were deleted in a read-only transaction!")
+                assert(deletedIndexes.isEmpty, "Indexes were deleted in a read-only transaction!")
+                assert(deletedPages.isEmpty, "Pages were deleted in a read-only transaction!")
+                return
+            }
+
+            /// If the transaction has a parent, offload responsibility to it to persist the changes along with other children.
             if let parent {
-                /// If the transaction is read-only, stop here without applying anything to the parent.
-                guard !options.contains(.readOnly) else {
-                    assert(entryMutations.isEmpty, "Entries were mutated in a read-only transaction!")
-                    assert(createdRootObjects.isEmpty, "Root objects were created in a read-only transaction!")
-                    assert(createdIndexes.isEmpty, "Indexes were created in a read-only transaction!")
-                    assert(createdPages.isEmpty, "Pages were created in a read-only transaction!")
-                    assert(deletedRootObjects.isEmpty, "Root objects were deleted in a read-only transaction!")
-                    assert(deletedIndexes.isEmpty, "Indexes were deleted in a read-only transaction!")
-                    assert(deletedPages.isEmpty, "Pages were deleted in a read-only transaction!")
-                    return
-                }
 //                print("[CDS] Offloading persist to parent \(transactionIndex) - \(options)")
                 try await parent.apply(
                     rootObjects: rootObjects,

Tests/CodableDatastoreTests/DiskPersistenceDatastoreTests.swift

@@ -915,6 +915,162 @@ final class DiskPersistenceDatastoreTests: XCTestCase, @unchecked Sendable {
         }
     }
 
+    func testReadOnlyTransactionDoesNotOverrideWrittenTransactions() async throws {
+        struct TestFormat: DatastoreFormat {
+            enum Version: Int, CaseIterable {
+                case zero
+            }
+
+            struct Instance: Codable, Identifiable {
+                var id: Int
+                var value: String
+            }
+
+            static let defaultKey: DatastoreKey = "test"
+            static let currentVersion = Version.zero
+        }
+
+        let persistence = try DiskPersistence(readWriteURL: temporaryStoreURL)
+        try await persistence.createPersistenceIfNecessary()
+
+        let datastore = Datastore.JSONStore(
+            persistence: persistence,
+            format: TestFormat.self,
+            migrations: [
+                .zero: { data, decoder in
+                    try decoder.decode(TestFormat.Instance.self, from: data)
+                }
+            ]
+        )
+
+        let valueBank = [
+            "Hello, World!",
+            "My name is Dimitri",
+            "Writen using CodableDatastore",
+            "Swift is better than Objective-C, there, I said it",
+            "Twenty Three is Number One"
+        ]
+
+        try await persistence.perform {
+            for id in 0..<10 {
+                try await datastore.persist(.init(id: id, value: valueBank.randomElement()!))
+            }
+        }
+
+        var totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 10)
+
+        let (startReadingTask, startReadingContinuation) = await Task.makeUnresolved()
+        let (didStartReadingTask, didStartReadingContinuation) = await Task.makeUnresolved()
+
+        let readTask = Task {
+            let allEntries = datastore.load(...)
+
+            didStartReadingContinuation.resume()
+            await startReadingTask.value
+
+            var count = 0
+            for try await _ in allEntries {
+                count += 1
+            }
+        }
+
+        await didStartReadingTask.value
+
+        try await persistence.perform {
+            for id in 10..<20 {
+                try await datastore.persist(.init(id: id, value: valueBank.randomElement()!))
+            }
+        }
+        totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 20)
+
+        startReadingContinuation.resume()
+        try await readTask.value
+
+        totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 20)
+    }
+
+    func testNestedReadOnlyTransactionDoesNotOverrideWrittenTransactions() async throws {
+        struct TestFormat: DatastoreFormat {
+            enum Version: Int, CaseIterable {
+                case zero
+            }
+
+            struct Instance: Codable, Identifiable {
+                var id: Int
+                var value: String
+            }
+
+            static let defaultKey: DatastoreKey = "test"
+            static let currentVersion = Version.zero
+        }
+
+        let persistence = try DiskPersistence(readWriteURL: temporaryStoreURL)
+        try await persistence.createPersistenceIfNecessary()
+
+        let datastore = Datastore.JSONStore(
+            persistence: persistence,
+            format: TestFormat.self,
+            migrations: [
+                .zero: { data, decoder in
+                    try decoder.decode(TestFormat.Instance.self, from: data)
+                }
+            ]
+        )
+
+        let valueBank = [
+            "Hello, World!",
+            "My name is Dimitri",
+            "Writen using CodableDatastore",
+            "Swift is better than Objective-C, there, I said it",
+            "Twenty Three is Number One"
+        ]
+
+        try await persistence.perform {
+            for id in 0..<10 {
+                try await datastore.persist(.init(id: id, value: valueBank.randomElement()!))
+            }
+        }
+
+        var totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 10)
+
+        let (startReadingTask, startReadingContinuation) = await Task.makeUnresolved()
+        let (didStartReadingTask, didStartReadingContinuation) = await Task.makeUnresolved()
+
+        let readTask = Task {
+            try await persistence.perform(options: .readOnly) {
+                let allEntries = datastore.load(...)
+
+                didStartReadingContinuation.resume()
+                await startReadingTask.value
+
+                var count = 0
+                for try await _ in allEntries {
+                    count += 1
+                }
+            }
+        }
+
+        await didStartReadingTask.value
+
+        try await persistence.perform {
+            for id in 10..<20 {
+                try await datastore.persist(.init(id: id, value: valueBank.randomElement()!))
+            }
+        }
+        totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 20)
+
+        startReadingContinuation.resume()
+        try await readTask.value
+
+        totalCount = try await datastore.count
+        XCTAssertEqual(totalCount, 20)
+    }
+
     func testTakingSnapshots() async throws {
         struct TestFormat: DatastoreFormat {
             enum Version: Int, CaseIterable {

Tests/CodableDatastoreTests/Task+Unresolved.swift

@@ -0,0 +1,24 @@
+//
+//  Task+Unresolved.swift
+//  CodableDatastore
+//
+//  Created by Dimitri Bouniol on 12/22/25.
+//  Copyright © 2023-25 Mochi Development, Inc. All rights reserved.
+//
+
+extension Task where Success == Void, Failure == Never {
+    static func makeUnresolved() async -> (
+        task: Task<Success, Failure>,
+        continuation: CheckedContinuation<Success, Failure>
+    ) {
+        var task: Task<Success, Failure>?
+        let continuation = await withCheckedContinuation { factoryContinuation in
+            task = Task {
+                await withCheckedContinuation { taskContinuation in
+                    factoryContinuation.resume(returning: taskContinuation)
+                }
+            }
+        }
+        return (task!, continuation)
+    }
+}