Repository: immerjs/immer
Pull request #1094 (2024-02-27 16:14:11)

Make  `applyPatches` to accept  `readonly Patch[]`
My main goal is for `applyPatches` to accept `readonly Patch[]` as there is no reason why it shouldn't accept it. If you think that other changes here are too risky (like returning `readonly Patch[]` from `produceWithPatches`) then I can revert those bits of this change. 

mweststrate: Yeah that looks great! I'm not 100% sure about the returned patches indeed, as people might be postprocessing those in a mutable manner. So probably safer to not change right away. (Feel free to set up a separate PR to park for the next major)
mweststrate: Looks like some of the tests fail, but overall agree with the idea :) 
Andarist: @mweststrate I adjusted the PR as requested. There are still some test failures here but they are unrelated to the change - the same ones can be seen `main`
mweststrate: I didn't use GitHub for too long and can't find the rebase button anymore, but master should be fixed now.
Andarist: Just rebased this on top of `main` - it should be ready to go

Patch:
diff --git a/.gitignore b/.gitignore
index 69ff4b3..ca80435 100644
--- a/.gitignore
+++ b/.gitignore
@@ -63,3 +63,5 @@ website/build
 website/.docusaurus
 .rts2*
 .gitpod.yml
+
+.watchman-cookie*
diff --git a/package.json b/package.json
index ee4cd40..e36d3e6 100644
--- a/package.json
+++ b/package.json
@@ -5,6 +5,7 @@
   "main": "./dist/cjs/index.js",
   "module": "./dist/immer.legacy-esm.js",
   "exports": {
+    "./package.json": "./package.json",
     ".": {
       "types": "./dist/immer.d.ts",
       "import": "./dist/immer.mjs",
diff --git a/src/core/immerClass.ts b/src/core/immerClass.ts
index 6c673e0..f827361 100644
--- a/src/core/immerClass.ts
+++ b/src/core/immerClass.ts
@@ -31,11 +31,16 @@ interface ProducersFns {
 	produceWithPatches: IProduceWithPatches
 }
 
+export type StrictMode = boolean | "class_only";
+
 export class Immer implements ProducersFns {
 	autoFreeze_: boolean = true
-	useStrictShallowCopy_: boolean = false
+	useStrictShallowCopy_: StrictMode = false
 
-	constructor(config?: {autoFreeze?: boolean; useStrictShallowCopy?: boolean}) {
+	constructor(config?: {
+		autoFreeze?: boolean
+		useStrictShallowCopy?: StrictMode
+	}) {
 		if (typeof config?.autoFreeze === "boolean")
 			this.setAutoFreeze(config!.autoFreeze)
 		if (typeof config?.useStrictShallowCopy === "boolean")
@@ -163,11 +168,11 @@ export class Immer implements ProducersFns {
 	 *
 	 * By default, immer does not copy the object descriptors such as getter, setter and non-enumrable properties.
 	 */
-	setUseStrictShallowCopy(value: boolean) {
+	setUseStrictShallowCopy(value: StrictMode) {
 		this.useStrictShallowCopy_ = value
 	}
 
-	applyPatches<T extends Objectish>(base: T, patches: Patch[]): T {
+	applyPatches<T extends Objectish>(base: T, patches: readonly Patch[]): T {
 		// If a patch replaces the entire state, take that replacement as base
 		// before applying patches
 		let i: number
diff --git a/src/immer.ts b/src/immer.ts
index 687cc2a..0199848 100644
--- a/src/immer.ts
+++ b/src/immer.ts
@@ -8,9 +8,11 @@ import {
 
 export {
 	Draft,
+	WritableDraft,
 	Immutable,
 	Patch,
 	PatchListener,
+	Producer,
 	original,
 	current,
 	isDraft,
@@ -18,7 +20,8 @@ export {
 	NOTHING as nothing,
 	DRAFTABLE as immerable,
 	freeze,
-	Objectish
+	Objectish,
+	StrictMode
 } from "./internal"
 
 const immer = new Immer()
diff --git a/src/plugins/patches.ts b/src/plugins/patches.ts
index e82e999..934e0b9 100644
--- a/src/plugins/patches.ts
+++ b/src/plugins/patches.ts
@@ -211,7 +211,7 @@ export function enablePatches() {
 		})
 	}
 
-	function applyPatches_<T>(draft: T, patches: Patch[]): T {
+	function applyPatches_<T>(draft: T, patches: readonly Patch[]): T {
 		patches.forEach(patch => {
 			const {path, op} = patch
 
diff --git a/src/utils/common.ts b/src/utils/common.ts
index fb4a768..692157b 100644
--- a/src/utils/common.ts
+++ b/src/utils/common.ts
@@ -8,7 +8,8 @@ import {
 	AnySet,
 	ImmerState,
 	ArchType,
-	die
+	die,
+	StrictMode
 } from "../internal"
 
 export const getPrototypeOf = Object.getPrototypeOf
@@ -62,7 +63,7 @@ export function original(value: Drafted<any>): any {
 
 /**
  * Each iterates a map, set or array.
- * Or, if any other kind of of object all it's own properties.
+ * Or, if any other kind of object, all of its own properties.
  * Regardless whether they are enumerable or symbols
  */
 export function each<T extends Objectish>(
@@ -140,7 +141,7 @@ export function latest(state: ImmerState): any {
 }
 
 /*#__PURE__*/
-export function shallowCopy(base: any, strict: boolean) {
+export function shallowCopy(base: any, strict: StrictMode) {
 	if (isMap(base)) {
 		return new Map(base)
 	}
@@ -149,36 +150,41 @@ export function shallowCopy(base: any, strict: boolean) {
 	}
 	if (Array.isArray(base)) return Array.prototype.slice.call(base)
 
-	if (!strict && isPlainObject(base)) {
-		if (!getPrototypeOf(base)) {
-			const obj = Object.create(null)
-			return Object.assign(obj, base)
+	const isPlain = isPlainObject(base)
+
+	if (strict === true || (strict === "class_only" && !isPlain)) {
+		// Perform a strict copy
+		const descriptors = Object.getOwnPropertyDescriptors(base)
+		delete descriptors[DRAFT_STATE as any]
+		let keys = Reflect.ownKeys(descriptors)
+		for (let i = 0; i < keys.length; i++) {
+			const key: any = keys[i]
+			const desc = descriptors[key]
+			if (desc.writable === false) {
+				desc.writable = true
+				desc.configurable = true
+			}
+			// like object.assign, we will read any _own_, get/set accessors. This helps in dealing
+			// with libraries that trap values, like mobx or vue
+			// unlike object.assign, non-enumerables will be copied as well
+			if (desc.get || desc.set)
+				descriptors[key] = {
+					configurable: true,
+					writable: true, // could live with !!desc.set as well here...
+					enumerable: desc.enumerable,
+					value: base[key]
+				}
 		}
-		return {...base}
-	}
-
-	const descriptors = Object.getOwnPropertyDescriptors(base)
-	delete descriptors[DRAFT_STATE as any]
-	let keys = Reflect.ownKeys(descriptors)
-	for (let i = 0; i < keys.length; i++) {
-		const key: any = keys[i]
-		const desc = descriptors[key]
-		if (desc.writable === false) {
-			desc.writable = true
-			desc.configurable = true
+		return Object.create(getPrototypeOf(base), descriptors)
+	} else {
+		// perform a sloppy copy
+		const proto = getPrototypeOf(base)
+		if (proto !== null && isPlain) {
+			return {...base} // assumption: better inner class optimization than the assign below
 		}
-		// like object.assign, we will read any _own_, get/set accessors. This helps in dealing
-		// with libraries that trap values, like mobx or vue
-		// unlike object.assign, non-enumerables will be copied as well
-		if (desc.get || desc.set)
-			descriptors[key] = {
-				configurable: true,
-				writable: true, // could live with !!desc.set as well here...
-				enumerable: desc.enumerable,
-				value: base[key]
-			}
+		const obj = Object.create(proto)
+		return Object.assign(obj, base)
 	}
-	return Object.create(getPrototypeOf(base), descriptors)
 }
 
 /**
diff --git a/src/utils/plugins.ts b/src/utils/plugins.ts
index 36cc1d7..fede08f 100644
--- a/src/utils/plugins.ts
+++ b/src/utils/plugins.ts
@@ -24,7 +24,7 @@ const plugins: {
 			patches: Patch[],
 			inversePatches: Patch[]
 		): void
-		applyPatches_<T>(draft: T, patches: Patch[]): T
+		applyPatches_<T>(draft: T, patches: readonly Patch[]): T
 	}
 	MapSet?: {
 		proxyMap_<T extends AnyMap>(target: T, parent?: ImmerState): T
diff --git a/website/docs/complex-objects.md b/website/docs/complex-objects.md
index 985482c..b98b430 100644
--- a/website/docs/complex-objects.md
+++ b/website/docs/complex-objects.md
@@ -7,8 +7,6 @@ title: Classes
 <div data-ea-publisher="immerjs" data-ea-type="image" className="horizontal bordered"></div>
 </center>
 
-By default, Immer does not strictly handle Plain object's non-eumerable properties such as getters/setters for performance reason. If you want this behavior to be strict, you can opt-in with `useStrictShallowCopy(true)`.
-
 Plain objects (objects without a prototype), arrays, `Map`s and `Set`s are always drafted by Immer. Every other object must use the `immerable` symbol to mark itself as compatible with Immer. When one of these objects is mutated within a producer, its prototype is preserved between copies.
 
 ```js
@@ -61,15 +59,17 @@ console.log(clock2 instanceof Clock) // true
 The semantics on how classes are drafted are as follows:
 
 1. A draft of a class is a fresh object but with the same prototype as the original object.
-1. When creating a draft, Immer will copy all _own_ properties from the base to the draft.This includes non-enumerable and symbolic properties.
+1. When creating a draft, Immer will copy all _own_ properties from the base to the draft.This includes (in strict mode) non-enumerable and symbolic properties.
 1. _Own_ getters will be invoked during the copy process, just like `Object.assign` would.
-1. Inherited getters and methods will remain as is and be inherited by the draft.
+1. Inherited getters and methods will remain as is and be inherited by the draft, as they are stored on the prototype which is untouched.
 1. Immer will not invoke constructor functions.
 1. The final instance will be constructed with the same mechanism as the draft was created.
 1. Only getters that have a setter as well will be writable in the draft, as otherwise the value can't be copied back.
 
 Because Immer will dereference own getters of objects into normal properties, it is possible to use objects that use getter/setter traps on their fields, like MobX and Vue do.
 
+Note that, by default, Immer does not strictly handle object's non-enumerable properties such as getters/setters for performance reason. If you want this behavior to be strict, you can opt-in with `useStrictShallowCopy(config)`. Use `true` to always copy strict, or `"class_only"` to only copy class instances strictly but use the faster loose copying for plain objects. The default is `false`. (Remember, regardless of strict mode, own getters / setters are always copied _by value_. There is currently no config to copy descriptors as-is. Feature request / PR welcome).
+
 Immer does not support exotic / engine native objects such as DOM Nodes or Buffers, nor is subclassing Map, Set or arrays supported and the `immerable` symbol can't be used on them.
 
 So when working for example with `Date` objects, you should always create a new `Date` instance instead of mutating an existing `Date` object.
diff --git a/website/yarn.lock b/website/yarn.lock
index 6f4eb56..422400b 100644
--- a/website/yarn.lock
+++ b/website/yarn.lock
@@ -2670,13 +2670,13 @@ binary-extensions@^2.0.0:
   resolved "https://registry.yarnpkg.com/binary-extensions/-/binary-extensions-2.2.0.tgz#75f502eeaf9ffde42fc98829645be4ea76bd9e2d"
   integrity sha512-jDctJ/IVQbZoJykoeHbhXpOlNBqGNcwXJKJog42E5HDPUwQTSdjCHdihjj0DlnheQ7blbT6dHOafNAiS8ooQKA==
 
-body-parser@1.20.1:
-  version "1.20.1"
-  resolved "https://registry.yarnpkg.com/body-parser/-/body-parser-1.20.1.tgz#b1812a8912c195cd371a3ee5e66faa2338a5c668"
-  integrity sha512-jWi7abTbYwajOytWCQc37VulmWiRae5RyTpaCyDcS5/lMdtwSz5lOpDE67srw/HYe35f1z3fDQw+3txg7gNtWw==
+body-parser@1.20.2:
+  version "1.20.2"
+  resolved "https://registry.yarnpkg.com/body-parser/-/body-parser-1.20.2.tgz#6feb0e21c4724d06de7ff38da36dad4f57a747fd"
+  integrity sha512-ml9pReCu3M61kGlqoTm2umSXTlRTuGTx0bfYj+uIUKKYycG5NtSbeetV3faSU6R7ajOPw0g/J1PvK4qNy7s5bA==
   dependencies:
     bytes "3.1.2"
-    content-type "~1.0.4"
+    content-type "~1.0.5"
     debug "2.6.9"
     depd "2.0.0"
     destroy "1.2.0"
@@ -2684,7 +2684,7 @@ body-parser@1.20.1:
     iconv-lite "0.4.24"
     on-finished "2.4.1"
     qs "6.11.0"
-    raw-body "2.5.1"
+    raw-body "2.5.2"
     type-is "~1.6.18"
     unpipe "1.0.0"
 
@@ -3138,6 +3138,11 @@ content-type@~1.0.4:
   resolved "https://registry.yarnpkg.com/content-type/-/content-type-1.0.4.tgz#e138cc75e040c727b1966fe5e5f8c9aee256fe3b"
   integrity sha512-hIP3EEPs8tB9AT1L+NUqtwOAps4mk2Zob89MWXMHjHWg9milF/j4osnnQLXBCBFBk/tvIG/tUc9mOUJiPBhPXA==
 
+content-type@~1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/content-type/-/content-type-1.0.5.tgz#8b773162656d1d1086784c8f23a54ce6d73d7918"
+  integrity sha512-nTjqfcBFEipKdXCv4YDQWCfmcLZKm81ldF0pAopTvyrFGVbcR6P/VAAd5G7N+0tTr8QqiU0tFadD6FK4NtJwOA==
+
 convert-source-map@^1.7.0:
   version "1.7.0"
   resolved "https://registry.yarnpkg.com/convert-source-map/-/convert-source-map-1.7.0.tgz#17a2cb882d7f77d3490585e2ce6c524424a3a442"
@@ -3150,10 +3155,10 @@ cookie-signature@1.0.6:
   resolved "https://registry.yarnpkg.com/cookie-signature/-/cookie-signature-1.0.6.tgz#e303a882b342cc3ee8ca513a79999734dab3ae2c"
   integrity sha512-QADzlaHc8icV8I7vbaJXJwod9HWYp8uCqf1xa4OfNu1T7JVxQIrUgOWtHdNDtPiywmFbiS12VjotIXLrKM3orQ==
 
-cookie@0.5.0:
-  version "0.5.0"
-  resolved "https://registry.yarnpkg.com/cookie/-/cookie-0.5.0.tgz#d1f5d71adec6558c58f389987c366aa47e994f8b"
-  integrity sha512-YZ3GUyn/o8gfKJlnlX7g7xq4gyO6OSuhGPKaaGssGB2qgDUS0gPgtTvoyZLTt9Ab6dC4hfc9dV5arkvc/OCmrw==
+cookie@0.6.0:
+  version "0.6.0"
+  resolved "https://registry.yarnpkg.com/cookie/-/cookie-0.6.0.tgz#2798b04b071b0ecbff0dbb62a505a8efa4e19051"
+  integrity sha512-U71cyTamuh1CRNCfpGY6to28lxvNwPG4Guz/EVjgf3Jmzv0vlDp1atT9eS5dDjMYHucpHbWns6Lwf3BKz6svdw==
 
 copy-text-to-clipboard@^3.0.1:
   version "3.0.1"
@@ -3814,16 +3819,16 @@ execa@^5.0.0:
     strip-final-newline "^2.0.0"
 
 express@^4.17.3:
-  version "4.18.2"
-  resolved "https://registry.yarnpkg.com/express/-/express-4.18.2.tgz#3fabe08296e930c796c19e3c516979386ba9fd59"
-  integrity sha512-5/PsL6iGPdfQ/lKM1UuielYgv3BUoJfz1aUwU9vHZ+J7gyvwdQXFEBIEIaxeGf0GIcreATNyBExtalisDbuMqQ==
+  version "4.19.2"
+  resolved "https://registry.yarnpkg.com/express/-/express-4.19.2.tgz#e25437827a3aa7f2a827bc8171bbbb664a356465"
+  integrity sha512-5T6nhjsT+EOMzuck8JjBHARTHfMht0POzlA60WV2pMD3gyXw2LZnZ+ueGdNxG+0calOJcWKbpFcuzLZ91YWq9Q==
   dependencies:
     accepts "~1.3.8"
     array-flatten "1.1.1"
-    body-parser "1.20.1"
+    body-parser "1.20.2"
     content-disposition "0.5.4"
     content-type "~1.0.4"
-    cookie "0.5.0"
+    cookie "0.6.0"
     cookie-signature "1.0.6"
     debug "2.6.9"
     depd "2.0.0"
@@ -3989,9 +3994,9 @@ find-up@^5.0.0:
     path-exists "^4.0.0"
 
 follow-redirects@^1.0.0, follow-redirects@^1.14.7:
-  version "1.15.5"
-  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.5.tgz#54d4d6d062c0fa7d9d17feb008461550e3ba8020"
-  integrity sha512-vSFWUON1B+yAw1VN4xMfxgn5fTUiaOzAJCKBwIIgT/+7CuGy9+r+5gITvP62j3RmaD5Ph65UaERdOSRGUzZtgw==
+  version "1.15.6"
+  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.6.tgz#7f815c0cda4249c74ff09e95ef97c23b5fd0399b"
+  integrity sha512-wWN62YITEaOpSK584EZXJafH1AGpO8RVgElfkuXbTOrPX4fIfOyEpW/CsiNd8JdYrAoOvafRTOEnvsO++qCqFA==
 
 fork-ts-checker-webpack-plugin@^6.5.0:
   version "6.5.2"
@@ -6149,10 +6154,10 @@ range-parser@^1.2.1, range-parser@~1.2.1:
   resolved "https://registry.yarnpkg.com/range-parser/-/range-parser-1.2.1.tgz#3cf37023d199e1c24d1a55b84800c2f3e6468031"
   integrity sha512-Hrgsx+orqoygnmhFbKaHE6c296J+HTAQXoxEF6gNupROmmGJRoyzfG3ccAveqCBrwr/2yxQ5BVd/GTl5agOwSg==
 
-raw-body@2.5.1:
-  version "2.5.1"
-  resolved "https://registry.yarnpkg.com/raw-body/-/raw-body-2.5.1.tgz#fe1b1628b181b700215e5fd42389f98b71392857"
-  integrity sha512-qqJBtEyVgS0ZmPGdCFPWJ3FreoqvG4MVQln/kCgF7Olq95IbOp0/BWyMwbdtn4VTvkM8Y7khCQ2Xgk/tcrCXig==
+raw-body@2.5.2:
+  version "2.5.2"
+  resolved "https://registry.yarnpkg.com/raw-body/-/raw-body-2.5.2.tgz#99febd83b90e08975087e8f1f9419a149366b68a"
+  integrity sha512-8zGqypfENjCIqGhgXToC8aB2r7YrBX+AQAfIPs/Mlk+BtPTztOvTS01NRW/3Eh60J+a48lt8qsCzirQ6loCVfA==
   dependencies:
     bytes "3.1.2"
     http-errors "2.0.0"
@@ -7607,9 +7612,9 @@ webpack-bundle-analyzer@^4.5.0:
     ws "^7.3.1"
 
 webpack-dev-middleware@^5.3.1:
-  version "5.3.3"
-  resolved "https://registry.yarnpkg.com/webpack-dev-middleware/-/webpack-dev-middleware-5.3.3.tgz#efae67c2793908e7311f1d9b06f2a08dcc97e51f"
-  integrity sha512-hj5CYrY0bZLB+eTO+x/j67Pkrquiy7kWepMHmUMoPsmcUaeEnQJqFzHJOyxgWlq746/wUuA64p9ta34Kyb01pA==
+  version "5.3.4"
+  resolved "https://registry.yarnpkg.com/webpack-dev-middleware/-/webpack-dev-middleware-5.3.4.tgz#eb7b39281cbce10e104eb2b8bf2b63fce49a3517"
+  integrity sha512-BVdTqhhs+0IfoeAf7EoH5WE+exCmqGerHfDM0IL096Px60Tq2Mn9MAbnaGUe6HiMa41KMCYF19gyzZmBcq/o4Q==
   dependencies:
     colorette "^2.0.10"
     memfs "^3.4.3"


Test patch:
diff --git a/__tests__/not-strict-copy.ts b/__tests__/not-strict-copy.ts
index 474d652..9414302 100644
--- a/__tests__/not-strict-copy.ts
+++ b/__tests__/not-strict-copy.ts
@@ -1,37 +1,75 @@
-import {produce, setUseStrictShallowCopy} from "../src/immer"
+import {
+	immerable,
+	produce,
+	setUseStrictShallowCopy,
+	setAutoFreeze,
+	StrictMode
+} from "../src/immer"
 
-describe("setUseStrictShallowCopy(true)", () => {
-	test("keep descriptors", () => {
-		setUseStrictShallowCopy(true)
+describe.each([true, false, "class_only" as const])(
+	"setUseStrictShallowCopy(true)",
+	(strictMode: StrictMode) => {
+		test("keep descriptors, mode: " + strictMode, () => {
+			setUseStrictShallowCopy(strictMode)
 
-		const base: Record<string, unknown> = {}
-		Object.defineProperty(base, "foo", {
-			value: "foo",
-			writable: false,
-			configurable: 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"
+			})
+			if (strictMode === true) {
+				expect(Object.getOwnPropertyDescriptor(copy, "foo")).toStrictEqual(
+					Object.getOwnPropertyDescriptor(base, "foo")
+				)
+			} else {
+				expect(Object.getOwnPropertyDescriptor(copy, "foo")).toBeUndefined()
+			}
 		})
-		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"
+
+		test("keep non-enumerable class descriptors, mode: " + strictMode, () => {
+			setUseStrictShallowCopy(strictMode)
+			setAutoFreeze(false)
+
+			class X {
+				[immerable] = true
+				foo = "foo"
+				bar!: string
+				constructor() {
+					Object.defineProperty(this, "bar", {
+						get() {
+							return this.foo + "bar"
+						},
+						configurable: false,
+						enumerable: false
+					})
+				}
+
+				get baz() {
+					return this.foo + "baz"
+				}
+			}
+
+			const copy = produce(new X(), (draft: any) => {
+				draft.foo = "FOO"
+			})
+
+			const strict = strictMode === true || strictMode === "class_only"
+
+			// descriptors on the prototype are unaffected, so this is still a getter
+			expect(copy.baz).toBe("FOObaz")
+			// descriptors on the instance are found, even when non-enumerable, and read during copy
+			// so new values won't be reflected
+			expect(copy.bar).toBe(strict ? "foobar" : undefined)
+
+			copy.foo = "fluff"
+			// not updated, the own prop became a value
+			expect(copy.bar).toBe(strict ? "foobar" : undefined)
+			// updated, it is still a getter
+			expect(copy.baz).toBe("fluffbaz")
 		})
-		expect(Object.getOwnPropertyDescriptor(copy, "foo")).toBeUndefined()
-	})
-})
+	}
+)
diff --git a/__tests__/produce.ts b/__tests__/produce.ts
index 22f0a31..f909368 100644
--- a/__tests__/produce.ts
+++ b/__tests__/produce.ts
@@ -8,7 +8,8 @@ import {
 	Immutable,
 	Immer,
 	enableMapSet,
-	enablePatches
+	enablePatches,
+	produceWithPatches
 } from "../src/immer"
 
 enableMapSet()
@@ -162,6 +163,20 @@ it("can apply patches", () => {
 	expect(applyPatches({}, patches)).toEqual({x: 4})
 })
 
+it("can apply readonly patches", () => {
+	const [, patches]: readonly [
+		{
+			x: number
+		},
+		readonly Patch[],
+		readonly Patch[]
+	] = produceWithPatches({x: 3}, d => {
+		d.x++
+	})
+
+	expect(applyPatches({}, patches)).toEqual({x: 4})
+})
+
 describe("curried producer", () => {
 	it("supports rest parameters", () => {
 		type State = {readonly a: 1}