fix(assign): fix overriding a nested object with null

src/object/assign.ts

@@ -25,12 +25,11 @@ export function assign<X extends Record<string | symbol | number, any>>(
   const merged = proto
     ? { ...initial }
     : Object.assign(Object.create(proto), initial)
-  for (const key in override) {
-    if (Object.prototype.hasOwnProperty.call(override, key)) {
-      merged[key] = isPlainObject(initial[key])
+  for (const key of Object.keys(override)) {
+    merged[key] =
+      isPlainObject(initial[key]) && isPlainObject(override[key])
         ? assign(initial[key], override[key])
         : override[key]
-    }
   }
   return merged
 }

tests/object/assign.test.ts

@@ -49,6 +49,10 @@ describe('assign', () => {
     const result = _.assign({}, { b: 'y' })
     expect(result).toEqual({ b: 'y' })
   })
+  test('handles null overriding nested object', () => {
+    const result = _.assign({ a: { b: { c: 1 } } }, { a: { b: null } })
+    expect(result).toEqual({ a: { b: null } })
+  })
   test('works with Object.create(null)', () => {
     const object = { a: Object.create(null) }
     object.a.b = 1