From 1dad4df4e34dca851fe3f82ad9ca3684d7fd5ccc Mon Sep 17 00:00:00 2001
From: Jay Meistrich <jmeistrich@gmail.com>
Date: Thu, 21 Sep 2023 18:15:51 +0200
Subject: [PATCH] Fix updateNodes not notifying when assigning

---
 src/ObservableObject.ts |  8 +++++++-
 tests/tests.test.ts     | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/ObservableObject.ts b/src/ObservableObject.ts
index 3deb4ca62..2dfb2c772 100644
--- a/src/ObservableObject.ts
+++ b/src/ObservableObject.ts
@@ -213,7 +213,7 @@ function updateNodes(parent: NodeValue, obj: Record<any, any> | Array<any> | und
         }
     }
 
-    if (obj && !isPrimitive(obj) && !parent.lazy) {
+    if (obj && !parent.lazy && !isPrimitive(obj)) {
         hasADiff = hasADiff || length !== lengthPrev;
         const isArrDiff = hasADiff;
         let didMove = false;
@@ -556,6 +556,12 @@ function setKey(node: NodeValue, key: string, newValue?: any, level?: number) {
     // Get the child node for updating and notifying
     const childNode: NodeValue = isRoot ? node : getChildNode(node, key);
 
+    if (childNode.lazy) {
+        // Make sure the node is activated when assigning because the node
+        // is never accessed through the proxy
+        peek(childNode);
+    }
+
     // Set the raw value on the parent object
     const { newValue: savedValue, prevValue, parentValue } = setNodeValue(childNode, newValue);
 
diff --git a/tests/tests.test.ts b/tests/tests.test.ts
index 3d9822d8b..62bc48031 100644
--- a/tests/tests.test.ts
+++ b/tests/tests.test.ts
@@ -511,6 +511,20 @@ describe('Listeners', () => {
             { path: ['test'], pathTypes: ['object'], valueAtPath: { test2: 'hi' }, prevAtPath: undefined },
         ]);
     });
+    test('Start undefined assign something', () => {
+        interface Data {
+            test?: undefined | { test2: string };
+        }
+        const obs = observable<Data>({});
+        const handler = expectChangeHandler(obs);
+
+        obs.assign({ test: { test2: 'hi' } });
+
+        // TODO: The previous value here is not totally correct because it filled out the path to make set work
+        expect(handler).toHaveBeenCalledWith({ test: { test2: 'hi' } }, { test: undefined }, [
+            { path: ['test'], pathTypes: ['object'], valueAtPath: { test2: 'hi' }, prevAtPath: undefined },
+        ]);
+    });
     test('Set with object should only fire listeners once', () => {
         interface Data {
             test: undefined | Record<string, string>;