fix: guard against undefined nested parent (valtiojs#41)

__tests__/07_nested_map_spec.ts

@@ -147,4 +147,67 @@ describe('issue #14', () => {
     expect(listener1).toBeCalledTimes(2);
     expect(listener2).toBeCalledTimes(2);
   });
+
+  it('nested map delete', async () => {
+    type State = Record<'items', {
+      [key: string]: {
+        color: string;
+      }
+    }>;
+    const doc = new Y.Doc();
+    const p = proxy<State>({ items: { item1: { color: 'blue' }, item2: { color: 'red' } } });
+    const m = doc.getMap('map') as any;
+
+    bind(p, m);
+
+    delete p.items.item1;
+    await Promise.resolve();
+
+    expect(m.get('items').get('item1')).toBeUndefined()
+    expect(m.get('items').get('item2')).toBeDefined()
+  });
+
+
+  it('nested map delete child and parent', async () => {
+    type State = Record<'parents', {
+      [key: string]: Record<'children', {
+        [key: string]: {
+          color: string;
+        }
+      }>
+    }>;
+    const doc = new Y.Doc();
+    const p = proxy<State>({
+      parents: {
+        parent1: {
+          children: {
+            child1: { color: 'blue' }
+          }
+        },
+        parent2: {
+          children: {
+            child2: { color: 'red' }
+          }
+        }
+      }
+    });
+    const m = doc.getMap('map') as any;
+
+    bind(p, m);
+
+    delete p.parents.parent1.children.child1;
+    delete p.parents.parent1;
+    await Promise.resolve();
+
+    expect(m.toJSON()).toStrictEqual({
+      parents: {
+        parent2: {
+          children: {
+            child2: { color: 'red' }
+          }
+        }
+      }
+    })
+  });
+
 });

src/index.ts

@@ -73,9 +73,13 @@ const getNestedValues = <T>(
   for (let i = 0; i < path.length; i += 1) {
     const k = path[i];
     if (yv instanceof Y.Map) {
+      // parent may already be deleted
+      if (!pv) break
       pv = pv[k];
       yv = yv.get(k as string);
     } else if (yv instanceof Y.Array) {
+      // parent may already be deleted
+      if (!pv) break
       const index = Number(k);
       pv = pv[k];
       yv = yv.get(index);