From 3a08e1ccabb9556ef1ffc4203427af986b3718c9 Mon Sep 17 00:00:00 2001
From: Kenneth Geisshirt <kenneth.geisshirt@mongodb.com>
Date: Tue, 14 Feb 2023 15:46:42 +0100
Subject: [PATCH] Fix a bug in parsing client reset configuration (#5288)

* Fix a bug in parsing client reset configuration
* Add default callbacks for recoverOrDiscard mode
---
 CHANGELOG.md      |  2 ++
 lib/extensions.js |  3 +++
 src/js_sync.hpp   | 26 ++++++++++++++------------
 types/index.d.ts  |  4 ++--
 4 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 881a0e9433..40ad4e9beb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,11 +9,13 @@
 
 ### Enhancements
 * Converting flexible sync Realms to bundled and local realms is now supported. ([realm/realm-core#6076](https://github.com/realm/realm-core/pull/6076))
+* For client reset mode `onRecoveryOrDiscard`, the `onDiscard` and `onRecovery` callbacks now have simple default values. ([#5288](https://github.com/realm/realm-js/pull/5288), since v11.1.0)
 
 ### Fixed
 * Fixed possible segfault in sync client where async callback was using object after being deallocated. ([realm/realm-core#6053](https://github.com/realm/realm-core/issues/6053), since v10.11.0)
 * Fixed crash when using client reset with recovery and flexible sync with a single subscription ([#6070](https://github.com/realm/realm-core/issues/6070), since v10.19.5)
 * If `path` is defined in the configuration, it will used for synced Realms too. Relative paths will be appended to a default prefix (prefix is computed using app id and user id). Absolute paths are left untouched. (since v10.0.0)
+* Fixed a bug related to parsing the client reset configuration. ([#5288](https://github.com/realm/realm-js/pull/5288), since v11.1.0)
 
 ### Compatibility
 * React Native >= v0.70.0
diff --git a/lib/extensions.js b/lib/extensions.js
index e581822b16..999ccecdc1 100644
--- a/lib/extensions.js
+++ b/lib/extensions.js
@@ -61,6 +61,8 @@ module.exports = function (realmConstructor) {
   realmConstructor._UUID = realmConstructor.BSON.UUID;
   const { DefaultNetworkTransport } = require("@realm/network-transport");
   realmConstructor._networkTransport = new DefaultNetworkTransport();
+  realmConstructor._defaultOnDiscardCallback = () => {};
+  realmConstructor._defaultOnRecoveryCallback = () => {};
 
   // Adds to cache when serializing an object for toJSON
   const addToCache = (cache, realmObj, value) => {
@@ -488,6 +490,7 @@ module.exports = function (realmConstructor) {
 
     realmConstructor.ClientResetMode = {
       Manual: "manual",
+      DiscardLocal: "discardLocal",
       DiscardUnsyncedChanges: "discardUnsyncedChanges",
       RecoverUnsyncedChanges: "recoverUnsyncedChanges",
       RecoverOrDiscardUnsyncedChanges: "recoverOrDiscardUnsyncedChanges",
diff --git a/src/js_sync.hpp b/src/js_sync.hpp
index 03b15ad7ae..89bf0a7d22 100644
--- a/src/js_sync.hpp
+++ b/src/js_sync.hpp
@@ -1303,21 +1303,23 @@ void SyncClass<T>::populate_sync_config(ContextType ctx, ObjectType realm_constr
                 }
 
                 case realm::ClientResyncMode::RecoverOrDiscard: {
-                    ValueType client_reset_after_value = Object::get_property(ctx, client_reset_object, "onDiscard");
-                    if (Value::is_undefined(ctx, client_reset_after_value)) {
-                        throw std::invalid_argument("'onDiscard' is required");
-                    }
-
-                    ValueType client_reset_recovery_value =
-                        Object::get_property(ctx, client_reset_object, "onRecovery");
-                    if (Value::is_undefined(ctx, client_reset_after_value)) {
-                        throw std::invalid_argument("'onRecovery' is required");
-                    }
+                    auto get_callback = [=](std::string callback_name, std::string default_callback_name) {
+                        ValueType callback_value = Object::get_property(ctx, client_reset_object, callback_name);
+                        if (Value::is_undefined(ctx, callback_value)) {
+                            auto realm = Value::validated_to_object(ctx, Object::get_global(ctx, "Realm"));
+                            auto default_callback_value = Value::validated_to_object(
+                                ctx, Object::get_property(ctx, realm, default_callback_name));
+                            return Value::validated_to_function(ctx, default_callback_value);
+                        }
+                        else {
+                            return Value::validated_to_function(ctx, callback_value);
+                        }
+                    };
 
                     FunctionType client_reset_discard_callback =
-                        Value::validated_to_function(ctx, client_reset_after_value);
+                        get_callback("onDiscard", "_defaultOnDiscardCallback");
                     FunctionType client_reset_recovery_callback =
-                        Value::validated_to_function(ctx, client_reset_recovery_value);
+                        get_callback("onRecovery", "_defaultOnRecoveryCallback");
 
                     auto client_reset_after_handler =
                         util::EventLoopDispatcher<void(SharedRealm, ThreadSafeReference, bool)>(
diff --git a/types/index.d.ts b/types/index.d.ts
index 1ff43e28f8..5ac56ae8b8 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -175,8 +175,8 @@ declare namespace Realm {
     interface ClientResetRecoveryOrDiscardConfiguration {
       mode: ClientResetMode.RecoverOrDiscardUnsyncedChanges;
       onBefore?: ClientResetBeforeCallback;
-      onRecovery: ClientResetAfterCallback;
-      onDiscard: ClientResetAfterCallback;
+      onRecovery?: ClientResetAfterCallback;
+      onDiscard?: ClientResetAfterCallback;
       onFallback?: ClientResetFallbackCallback;
     }