Support symbol properties (#10)

* support symbol properties

* fix type to support all peoperty keys

src/index.test.ts

@@ -18,6 +18,7 @@ type User = {
   emails: string[];
   toString: string;
   constructor: string | null;
+  [Symbol.isConcatSpreadable]: boolean;
 };
 
 describe("defaultComposer", () => {
@@ -38,6 +39,7 @@ describe("defaultComposer", () => {
       emails: ["[email protected]"],
       hobbies: ["programming"],
       toString: "I am Aral",
+      [Symbol.isConcatSpreadable]: false,
     };
 
     const originalObject = {
@@ -70,6 +72,7 @@ describe("defaultComposer", () => {
       hobbies: ["parkour", "computer science", "books", "nature"],
       toString: "I am Aral",
       constructor: null,
+      [Symbol.isConcatSpreadable]: false,
     };
 
     expect(defaultComposer<User>(defaults, originalObject)).toEqual(expected);
@@ -137,6 +140,30 @@ describe("defaultComposer", () => {
     expect(mockFn).toBeCalledTimes(1);
   });
 
+  it("should work with enumerable symbol properties", () => {
+    const tag = Symbol.for("tag");
+    const version = Symbol.for("version");
+    const createdAt = Symbol.for("createdAt");
+
+    const defaults = {
+      [tag]: "user",
+      [createdAt]: Date.UTC(2020, 1, 1),
+    };
+
+    Object.defineProperty(defaults, version, { value: 1, enumerable: false });
+
+    const object = {
+      [createdAt]: Date.UTC(2023, 6, 1),
+    };
+
+    const expected = {
+      [tag]: "user",
+      [createdAt]: Date.UTC(2023, 6, 1),
+    };
+
+    expect(defaultComposer<any>(defaults, object)).toEqual(expected);
+  });
+
   it("should work with a custom isDefaultableValue", () => {
     const defaults = {
       original: {

src/index.ts

@@ -1,6 +1,6 @@
 type isDefaultableValueInputType = {
   defaultableValue: boolean;
-  key: string;
+  key: PropertyKey;
   value: unknown;
 };
 
@@ -26,7 +26,7 @@ export function defaultComposer<T>(...args: Partial<T>[]): T {
 
 function compose<T>(defaults: Partial<T>, obj: Partial<T>): Partial<T> {
   const result: Partial<T> = {};
-  const allKeys = new Set([defaults, obj].flatMap(Object.keys));
+  const allKeys = new Set([defaults, obj].flatMap(getAllKeys));
 
   for (let key of allKeys) {
     const defaultsValue = defaults[key];
@@ -60,7 +60,7 @@ function isObject(value: any): boolean {
 
 function isEmptyObjectOrArray<T>(object: T): boolean {
   if (typeof object !== "object" || object === null) return false;
-  return Object.keys(object).length === 0;
+  return getAllKeys(object).length === 0;
 }
 
 function checkDefaultableValue({ value }: { value: unknown }): boolean {
@@ -78,3 +78,12 @@ function hasOwn<T extends PropertyKey>(
 ): key is T {
   return Object.prototype.hasOwnProperty.call(obj, key);
 }
+
+function getAllKeys(object: {}): PropertyKey[] {
+  return [
+    ...Object.keys(object),
+    ...Object.getOwnPropertySymbols(object).filter(
+      (key) => Object.getOwnPropertyDescriptor(object, key)?.enumerable
+    ),
+  ];
+}