feat(ValueObject): make it work with primitives

src/ValueObject.ts

@@ -1,20 +1,21 @@
 import DeepCompositeSymbol from './DeepCompositeSymbol';
+import { isObject } from './helpers';
 
 /**
  * Works somewhat similarly to Record in the Record & Tuple proposal:
  * https://github.com/tc39/proposal-record-tuple
  */
 // tslint:disable-next-line: variable-name
-const ValueObject = <A extends object>(
-  object: A,
-  filter?: (entry: [string, any]) => boolean,
-): A => {
-  const key = DeepCompositeSymbol(object, filter);
+const ValueObject = <A extends any>(target: A, filter?: (entry: [string, any]) => boolean): A => {
+  if (!isObject(target)) {
+    return target;
+  }
+  const key = DeepCompositeSymbol(target, filter);
   if (cache.has(key)) {
     return cache.get(key) as A;
   }
-  cache.set(key, object);
-  return object;
+  cache.set(key, target);
+  return target;
 };
 
 const cache = new Map<symbol, object>();

test/ValueObject.test.ts

@@ -34,4 +34,9 @@ describe(ValueObject.name, () => {
     expect(vO1).not.toBe(vO2);
     expect(ValueObject(vO2)).toBe(ValueObject(vO2));
   });
+
+  it('works with primitives', () => {
+    expect(() => ValueObject(null)).not.toThrow();
+    expect(() => ValueObject(undefined)).not.toThrow();
+  });
 });