Fix

Author: ardatan

.changeset/chilly-icons-guess.md

@@ -6,6 +6,6 @@ Fix the bug in `mergeDeep`;
 
 The following inputs and outputs are corrected;
 
-- `mergeDeep([{a:2} undefined])` - Any nullish values should be ignored so it should return `{a:2}`
+- `mergeDeep([{a:2}, undefined])` - Any nullish values should be ignored so it should return `{a:2}`
 - `mergeDeep([])` - no sources should return `undefined`
 - `mergeDeep([undefined])` - no sources should return `undefined`

packages/utils/src/mergeDeep.ts

@@ -52,10 +52,10 @@ export function mergeDeep<S extends any[]>(
   let firstObjectSource: any;
   if (respectPrototype) {
     firstObjectSource = sources.find(source => isObject(source));
-    if (output == null) {
-      output = {};
-    }
     if (firstObjectSource) {
+      if (output == null) {
+        output = {};
+      }
       Object.setPrototypeOf(output, Object.create(Object.getPrototypeOf(firstObjectSource)));
     }
   }