feat: implement useStrictShallowCopy

__tests__/not-strict-copy.ts

@@ -0,0 +1,39 @@
+import produce, {enableAllPlugins, setUseStrictShallowCopy} from "../src/immer"
+
+enableAllPlugins()
+
+describe("setUseStrictShallowCopy(true)", () => {
+	test("keep descriptors", () => {
+		setUseStrictShallowCopy(true)
+
+		const base: Record<string, unknown> = {}
+		Object.defineProperty(base, "foo", {
+			value: "foo",
+			writable: false,
+			configurable: false
+		})
+		const copy = produce(base, (draft: any) => {
+			draft.bar = "bar"
+		})
+		expect(Object.getOwnPropertyDescriptor(copy, "foo")).toStrictEqual(
+			Object.getOwnPropertyDescriptor(base, "foo")
+		)
+	})
+})
+
+describe("setUseStrictShallowCopy(false)", () => {
+	test("ignore descriptors", () => {
+		setUseStrictShallowCopy(false)
+
+		const base: Record<string, unknown> = {}
+		Object.defineProperty(base, "foo", {
+			value: "foo",
+			writable: false,
+			configurable: false
+		})
+		const copy = produce(base, (draft: any) => {
+			draft.bar = "bar"
+		})
+		expect(Object.getOwnPropertyDescriptor(copy, "foo")).toBeUndefined()
+	})
+})

src/core/current.ts

@@ -33,10 +33,14 @@ function currentImpl(value: any): any {
 			return state.base_
 		// Optimization: avoid generating new drafts during copying
 		state.finalized_ = true
-		copy = copyHelper(value, archType)
+		copy = copyHelper(
+			value,
+			archType,
+			state.scope_.immer_.useStrictShallowCopy_
+		)
 		state.finalized_ = false
 	} else {
-		copy = copyHelper(value, archType)
+		copy = copyHelper(value, archType, true)
 	}
 
 	each(copy, (key, childValue) => {
@@ -47,7 +51,7 @@ function currentImpl(value: any): any {
 	return archType === Archtype.Set ? new Set(copy) : copy
 }
 
-function copyHelper(value: any, archType: number): any {
+function copyHelper(value: any, archType: number, strict: boolean): any {
 	// creates a shallow copy, even if it is a map or set
 	switch (archType) {
 		case Archtype.Map:
@@ -56,5 +60,5 @@ function copyHelper(value: any, archType: number): any {
 			// Set will be cloned as array temporarily, so that we can replace individual items
 			return Array.from(value)
 	}
-	return shallowCopy(value)
+	return shallowCopy(value, strict)
 }

src/core/finalize.ts

@@ -83,7 +83,10 @@ function finalize(rootScope: ImmerScope, value: any, path?: PatchPath) {
 		const result =
 			// For ES5, create a good copy from the draft first, with added keys and without deleted keys.
 			state.type_ === ProxyType.ES5Object || state.type_ === ProxyType.ES5Array
-				? (state.copy_ = shallowCopy(state.draft_))
+				? (state.copy_ = shallowCopy(
+						state.draft_,
+						rootScope.immer_.useStrictShallowCopy_
+				  ))
 				: state.copy_
 		// Finalize all children of the copy
 		// For sets we clone before iterating, otherwise we can get in endless loop due to modifying during iteration, see #628

src/core/immerClass.ts

@@ -37,11 +37,19 @@ export class Immer implements ProducersFns {
 
 	autoFreeze_: boolean = true
 
-	constructor(config?: {useProxies?: boolean; autoFreeze?: boolean}) {
+	useStrictShallowCopy_: boolean = true
+
+	constructor(config?: {
+		useProxies?: boolean
+		autoFreeze?: boolean
+		useStrictShallowCopy?: boolean
+	}) {
 		if (typeof config?.useProxies === "boolean")
 			this.setUseProxies(config!.useProxies)
 		if (typeof config?.autoFreeze === "boolean")
 			this.setAutoFreeze(config!.autoFreeze)
+		if (typeof config?.useStrictShallowCopy === "boolean")
+			this.setUseStrictShallowCopy(config!.useStrictShallowCopy)
 	}
 
 	/**
@@ -195,6 +203,15 @@ export class Immer implements ProducersFns {
 		this.useProxies_ = value
 	}
 
+	/**
+	 * Pass false to disable strict shallow copy.
+	 *
+	 * By default, immer copies the object descriptors on creating new object.
+	 */
+	setUseStrictShallowCopy(value: boolean) {
+		this.useStrictShallowCopy_ = value
+	}
+
 	applyPatches<T extends Objectish>(base: T, patches: Patch[]): T {
 		// If a patch replaces the entire state, take that replacement as base
 		// before applying patches

src/core/proxy.ts

@@ -17,6 +17,7 @@ import {
 	createProxy,
 	ProxyType
 } from "../internal"
+import {ImmerScope} from "./scope"
 
 interface ProxyBaseState extends ImmerBaseState {
 	assigned_: {
@@ -273,8 +274,15 @@ export function markChanged(state: ImmerState) {
 	}
 }
 
-export function prepareCopy(state: {base_: any; copy_: any}) {
+export function prepareCopy(state: {
+	base_: any
+	copy_: any
+	scope_: ImmerScope
+}) {
 	if (!state.copy_) {
-		state.copy_ = shallowCopy(state.base_)
+		state.copy_ = shallowCopy(
+			state.base_,
+			state.scope_.immer_.useStrictShallowCopy_
+		)
 	}
 }

src/immer.ts

@@ -67,6 +67,13 @@ export const setAutoFreeze = immer.setAutoFreeze.bind(immer)
  */
 export const setUseProxies = immer.setUseProxies.bind(immer)
 
+/**
+ * Pass false to disable strict shallow copy.
+ *
+ * By default, immer copies the object descriptors on creating new object.
+ */
+export const setUseStrictShallowCopy = immer.setUseStrictShallowCopy.bind(immer)
+
 /**
  * Apply an array of Immer patches to the first argument.
  *

src/types/index.js.flow

@@ -84,6 +84,13 @@ declare export function setAutoFreeze(autoFreeze: boolean): void
  */
 declare export function setUseProxies(useProxies: boolean): void
 
+/**
+ * Pass false to disable strict shallow copy.
+ *
+ * By default, immer copies the object descriptors on creating new object.
+ */
+declare export function setUseStrictShallowCopy(useStrictShallowCopy: boolean): void
+
 declare export function applyPatches<S>(state: S, patches: Patch[]): S
 
 declare export function original<S>(value: S): S

src/utils/common.ts

@@ -162,8 +162,19 @@ export function latest(state: ImmerState): any {
 }
 
 /*#__PURE__*/
-export function shallowCopy(base: any) {
+export function shallowCopy(base: any, strict: boolean) {
 	if (Array.isArray(base)) return Array.prototype.slice.call(base)
+
+	if (!strict && isPlainObject(base)) {
+		const keys = Object.keys(base)
+		const obj: any = Object.create(Object.getPrototypeOf(base))
+		for (let i = 0; i < keys.length; i++) {
+			const key = keys[i]
+			obj[key] = base[key]
+		}
+		return obj
+	}
+
 	const descriptors = getOwnPropertyDescriptors(base)
 	delete descriptors[DRAFT_STATE as any]
 	let keys = ownKeys(descriptors)