feat(ValueObject): filter by key

src/DeepCompositeSymbol.ts

@@ -2,11 +2,13 @@ import Tuple from './Tuple';
 import { isObject } from './helpers';
 
 // tslint:disable-next-line: variable-name
-const DeepCompositeSymbol: typeof Tuple.symbol = ((object: any) => {
-  const entries = Object.entries(object);
+const DeepCompositeSymbol = ((object: any, keyFilter?: (key: string) => boolean) => {
+  const entries = keyFilter
+    ? Object.entries(object).filter(entry => keyFilter(entry[0]))
+    : Object.entries(object);
   // Recursively replace non-tuple object values with tuples
   entries.forEach(update);
-  return Tuple.unsafeSymbol(...Array.prototype.concat.apply([], entries));
+  return Tuple.unsafeSymbol(...flatten(entries));
 }) as any;
 
 const update = (entry: any) => {
@@ -16,4 +18,6 @@ const update = (entry: any) => {
   }
 };
 
+const flatten = (entries: any[][]) => Array.prototype.concat.apply([], entries);
+
 export default DeepCompositeSymbol;

src/ValueObject.ts

@@ -5,8 +5,8 @@ import DeepCompositeSymbol from './DeepCompositeSymbol';
  * https://github.com/tc39/proposal-record-tuple
  */
 // tslint:disable-next-line: variable-name
-const ValueObject = <A extends object>(object: A, filterKeys?: (key: string) => boolean): A => {
-  const key = DeepCompositeSymbol(object, filterKeys);
+const ValueObject = <A extends object>(object: A, keyFilter?: (key: string) => boolean): A => {
+  const key = DeepCompositeSymbol(object, keyFilter);
   if (cache.has(key)) {
     return cache.get(key) as A;
   }

test/DeepCompositeSymbol.test.ts

@@ -18,4 +18,12 @@ describe(DeepCompositeSymbol.name, () => {
     expect(DeepCompositeSymbol(o())).toBe(DeepCompositeSymbol(o()));
     expect(DeepCompositeSymbol(o())).not.toBe(DeepCompositeSymbol({}));
   });
+
+  it('allows filtering by key', () => {
+    const o1 = { a: { c: 1 }, b: 2, _d: 3 };
+    const o2 = { ...o1, _d: 4 };
+    const filter = (key: string) => !key.startsWith('_');
+    expect(DeepCompositeSymbol(o1, filter)).toBe(DeepCompositeSymbol(o2, filter));
+    expect(DeepCompositeSymbol(o1)).not.toBe(DeepCompositeSymbol(o2));
+  });
 });

test/ValueObject.test.ts

@@ -30,6 +30,7 @@ describe(ValueObject.name, () => {
     o.b = 3;
     const vO2 = ValueObject(o);
 
+    expect(vO2.b).toBe(o.b);
     expect(vO1).not.toBe(vO2);
     expect(ValueObject(vO2)).toBe(ValueObject(vO2));
   });