fix: undraftable values should not be cloned for patches, fixes #676

__tests__/patch.js

@@ -1119,3 +1119,31 @@ describe("#588", () => {
 		[{op: "add", path: ["num"], value: 42}]
 	)
 })
+
+test("#676 patching Date objects", () => {
+	class Test {
+		constructor() {
+			this.test = true
+		}
+		perform() {
+			return "tested!"
+		}
+	}
+
+	const [nextState, patches] = produceWithPatches({}, function(draft) {
+		draft.date = new Date(2020, 10, 10, 8, 8, 8, 3)
+		draft.test = new Test()
+	})
+
+	expect(nextState.date.toJSON()).toMatchInlineSnapshot(
+		`"2020-11-10T08:08:08.003Z"`
+	)
+	expect(nextState.test.perform()).toBe("tested!")
+
+	const rebuilt = applyPatches({}, patches)
+	expect(rebuilt.date).toBeInstanceOf(Date)
+	expect(rebuilt.date.toJSON()).toMatchInlineSnapshot(
+		`"2020-11-10T08:08:08.003Z"`
+	)
+	expect(rebuilt.date).toEqual(new Date(2020, 10, 10, 8, 8, 8, 3))
+})

src/plugins/patches.ts

@@ -25,7 +25,8 @@ import {
 	ArchtypeSet,
 	ArchtypeArray,
 	die,
-	isDraft
+	isDraft,
+	isDraftable
 } from "../internal"
 
 export function enablePatches() {
@@ -267,7 +268,7 @@ export function enablePatches() {
 	// (See failing test when deepClone just returns obj)
 	function deepClonePatchValue<T>(obj: T): T
 	function deepClonePatchValue(obj: any) {
-		if (!obj || typeof obj !== "object") return obj
+		if (!isDraftable(obj)) return obj
 		if (Array.isArray(obj)) return obj.map(deepClonePatchValue)
 		if (isMap(obj))
 			return new Map(