Fix(json-safe-extend): Prevent extending array members

Author: 1aron

packages/json-safe-extend/src/index.ts

@@ -12,14 +12,15 @@ export default function extend<T extends object>(...sources: (Partial<T> | null
 
             if (Array.isArray(val)) {
                 target[key] = val.map(item =>
-                    typeof item === 'object' && item !== null
-                        ? extend({}, item)
-                        : item
+                    Array.isArray(item)
+                        ? [...item] // shallow copy nested arrays
+                        : typeof item === 'object' && item !== null
+                            ? extend({}, item)
+                            : item
                 )
             } else if (
                 typeof val === 'object' &&
-                val !== null &&
-                !Array.isArray(val)
+                val !== null
             ) {
                 target[key] =
                     typeof src === 'object' && src !== null && !Array.isArray(src)

packages/json-safe-extend/tests/test.ts

@@ -285,4 +285,14 @@ test('symbol', ()=> {
         [C]: 3,
         [D]: 5
     })
+})
+
+test('array', () => {
+    const result = extend(
+        { a: [1, 2, [3, 4]] },
+        { a: [5, 6, [7, 8]] },
+    )
+    expect(result).toEqual({
+        a: [5, 6, [7, 8]]
+    })
 })