Allow creating notifiers inside write transactions before the first change

CHANGELOG.md

@@ -1,3 +1,23 @@
+x.y.z Release notes (yyyy-MM-dd)
+=============================================================
+### Enhancements
+* None.
+
+### Fixed
+* Registering new notifications inside write transactions before actually
+  making any changes is now actually allowed. This was supposed to be allowed
+  in 10.39.1, but it did not actually work due to some redundant validation.
+
+### Compatibility
+* Realm Studio: 14.0.1 or later.
+* APIs are backwards compatible with all previous releases in the 10.x.y series.
+* Carthage release for Swift is built with Xcode 15.1.0.
+* CocoaPods: 1.10 or later.
+* Xcode: 14.1-15.1.0.
+
+### Internal
+* Upgraded realm-core from ? to ?
+
 10.45.1 Release notes (2023-12-18)
 =============================================================
 

Realm/RLMCollection.mm

@@ -506,7 +506,12 @@ - (bool)invalidate {
     RLMClassInfo *info = collection.objectInfo;
     if (!queue) {
         [realm verifyNotificationsAreSupported:true];
-        token->_token = [collection addNotificationCallback:block keyPaths:info->keyPathArrayFromStringArray(keyPaths)];
+        try {
+            token->_token = [collection addNotificationCallback:block keyPaths:info->keyPathArrayFromStringArray(keyPaths)];
+        }
+        catch (const realm::Exception& e) {
+            @throw RLMException(e);
+        }
         return token;
     }
 

Realm/RLMObjectBase.mm

@@ -752,8 +752,13 @@ - (void)observe:(RLMObjectBase *)obj
             completion();
         }
     };
-    _token = _object.add_notification_callback(ObjectChangeCallbackWrapper{block, obj, completion},
-                                               obj->_info->keyPathArrayFromStringArray(keyPaths));
+    try {
+        _token = _object.add_notification_callback(ObjectChangeCallbackWrapper{block, obj, completion},
+                                                   obj->_info->keyPathArrayFromStringArray(keyPaths));
+    }
+    catch (const realm::Exception& e) {
+        @throw RLMException(e);
+    }
 }
 
 - (void)registrationComplete:(void (^)())completion {

Realm/RLMRealm.mm

@@ -550,9 +550,6 @@ - (void)verifyNotificationsAreSupported:(bool)isCollection {
     if (_realm->config().automatic_change_notifications && !_realm->can_deliver_notifications()) {
         @throw RLMException(@"Can only add notification blocks from within runloops.");
     }
-    if (isCollection && _realm->is_in_transaction()) {
-        @throw RLMException(@"Cannot register notification blocks from within write transactions.");
-    }
 }
 
 - (RLMNotificationToken *)addNotificationBlock:(RLMNotificationBlock)block {

Realm/Tests/AsyncTests.mm

@@ -859,11 +859,15 @@ - (void)testAsyncNotSupportedForReadOnlyRealms {
     }]);
 }
 
-- (void)testAsyncNotSupportedInWriteTransactions {
-    [RLMRealm.defaultRealm transactionWithBlock:^{
-        XCTAssertThrows([IntObject.allObjects addNotificationBlock:^(RLMResults *results, RLMCollectionChange *change, NSError *error) {
-            XCTFail(@"should not be called");
-        }]);
+- (void)testAsyncNotSupportedAfterMakingChangesInWriteTransactions {
+    RLMRealm *realm = [RLMRealm defaultRealm];
+    [realm transactionWithBlock:^{
+        XCTAssertNoThrow([IntObject.allObjects addNotificationBlock:^(RLMResults *, RLMCollectionChange *, NSError *) {}]);
+        [IntObject createInRealm:realm withValue:@[@0]];
+        RLMAssertThrowsWithReason([IntObject.allObjects addNotificationBlock:^(RLMResults *, RLMCollectionChange *, NSError *) {}],
+                                  @"Cannot create asynchronous query after making changes in a write transaction.");
+        RLMAssertThrowsWithReason([IntObject.allObjects[0] addNotificationBlock:^(BOOL, NSArray *, NSError *) {}],
+                                  @"Cannot create asynchronous query after making changes in a write transaction.");
     }];
 }
 

RealmSwift/Tests/ObjectTests.swift

@@ -18,7 +18,7 @@
 
 import XCTest
 import Realm
 import RealmSwift
 import Foundation
 import os.lock
 
@@ -1580,7 +1580,6 @@
 
     // This test consistently crashes inside the Swift runtime when building
     // with SPM.
-    #if !SWIFT_PACKAGE
     @MainActor
     @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
     func testAsyncSequenceObserve() async throws {
@@ -1588,7 +1587,7 @@
         let ex = Locked(expectation(description: "got value"))
         let task = Task { @MainActor in
             var value = 0
             for try await object in valuePublisher(obj).values {
                 XCTAssertIdentical(object, obj)
                 value += 1
                 XCTAssertEqual(object.intCol, value)
@@ -1608,7 +1607,6 @@
         task.cancel()
         _ = try await task.value
     }
-    #endif
 
     @MainActor
     @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
@@ -1616,10 +1614,10 @@
         let obj = try createObject()
         let ex = Locked(expectation(description: "got next"))
         let task = Task { @CustomGlobalActor in
             let realm = try await Realm(actor: CustomGlobalActor.shared)
             let obj = realm.objects(SwiftObject.self).first!
             var value = 0
             for try await change in changesetPublisher(obj).values {
                 guard case let .change(object, props) = change else {
                     return XCTFail("Expected .change, got \(change)")
                 }
@@ -1690,7 +1688,7 @@
                 group.addTask { @CustomGlobalActor in
                     waitingForRealm.withLock { $0 += 1 }
                     // can throw due to cancellation
                     guard let realm = try? await Realm(actor: CustomGlobalActor.shared) else {
                         waitingForRealm.withLock { $0 -= 1 }
                         return NotificationToken()
                     }