From 535097ab963710cf4137f858e262f198521ff72f Mon Sep 17 00:00:00 2001
From: Thomas Goyne <tg@realm.io>
Date: Thu, 14 Dec 2023 14:13:28 -0800
Subject: [PATCH] Allow creating notifiers inside write transactions before the
 first change

Core has allowed this for a while, but we had our own validation which made it not work.
---
 CHANGELOG.md                       | 20 ++++++++++++++++++++
 Realm/RLMCollection.mm             |  7 ++++++-
 Realm/RLMObjectBase.mm             |  9 +++++++--
 Realm/RLMRealm.mm                  |  3 ---
 Realm/Tests/AsyncTests.mm          | 14 +++++++++-----
 RealmSwift/Tests/ObjectTests.swift |  2 --
 6 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1d81a82d72..daedb02600 100644
--- a/CHANGELOG.md
+++ b/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)
 =============================================================
 
diff --git a/Realm/RLMCollection.mm b/Realm/RLMCollection.mm
index aebaf1eb63..6826e302db 100644
--- a/Realm/RLMCollection.mm
+++ b/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;
     }
 
diff --git a/Realm/RLMObjectBase.mm b/Realm/RLMObjectBase.mm
index 8dbf6f48b9..a31310fe43 100644
--- a/Realm/RLMObjectBase.mm
+++ b/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 {
diff --git a/Realm/RLMRealm.mm b/Realm/RLMRealm.mm
index 9109d0e0ba..268a65ad6f 100644
--- a/Realm/RLMRealm.mm
+++ b/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 {
diff --git a/Realm/Tests/AsyncTests.mm b/Realm/Tests/AsyncTests.mm
index 819c46b45b..854297da09 100644
--- a/Realm/Tests/AsyncTests.mm
+++ b/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.");
     }];
 }
 
diff --git a/RealmSwift/Tests/ObjectTests.swift b/RealmSwift/Tests/ObjectTests.swift
index 06918f6964..a29697d519 100644
--- a/RealmSwift/Tests/ObjectTests.swift
+++ b/RealmSwift/Tests/ObjectTests.swift
@@ -1580,7 +1580,6 @@ class ObjectTests: TestCase {
 
     // 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 {
@@ -1608,7 +1607,6 @@ class ObjectTests: TestCase {
         task.cancel()
         _ = try await task.value
     }
-    #endif
 
     @MainActor
     @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)