ReadonlyDeep: Skip constructor (#728)

sindresorhus · Oct 24, 2023 · 3ee234a · 3ee234a
1 parent 9baccc3
commit 3ee234a
Show file tree

Hide file tree

Showing 2 changed files with 32 additions and 21 deletions.
diff --git a/source/readonly-deep.d.ts b/source/readonly-deep.d.ts
@@ -38,28 +38,30 @@ Note that types containing overloaded functions are not made deeply readonly due
 */
 export type ReadonlyDeep<T> = T extends BuiltIns
 	? T
-	: T extends (...arguments_: any[]) => unknown
-		? {} extends ReadonlyObjectDeep<T>
-			? T
-			: HasMultipleCallSignatures<T> extends true
+	: T extends new (...args: any[]) => unknown
+		? T // Skip class constructors
+		: T extends (...arguments_: any[]) => unknown
+			? {} extends ReadonlyObjectDeep<T>
 				? T
-				: ((...arguments_: Parameters<T>) => ReturnType<T>) & ReadonlyObjectDeep<T>
-		: T extends Readonly<ReadonlyMap<infer KeyType, infer ValueType>>
-			? ReadonlyMapDeep<KeyType, ValueType>
-			: T extends Readonly<ReadonlySet<infer ItemType>>
-				? ReadonlySetDeep<ItemType>
-				: // Identify tuples to avoid converting them to arrays inadvertently; special case `readonly [...never[]]`, as it emerges undesirably from recursive invocations of ReadonlyDeep below.
-				T extends readonly [] | readonly [...never[]]
-					? readonly []
-					: T extends readonly [infer U, ...infer V]
-						? readonly [ReadonlyDeep<U>, ...ReadonlyDeep<V>]
-						: T extends readonly [...infer U, infer V]
-							? readonly [...ReadonlyDeep<U>, ReadonlyDeep<V>]
-							: T extends ReadonlyArray<infer ItemType>
-								? ReadonlyArray<ReadonlyDeep<ItemType>>
-								: T extends object
-									? ReadonlyObjectDeep<T>
-									: unknown;
+				: HasMultipleCallSignatures<T> extends true
+					? T
+					: ((...arguments_: Parameters<T>) => ReturnType<T>) & ReadonlyObjectDeep<T>
+			: T extends Readonly<ReadonlyMap<infer KeyType, infer ValueType>>
+				? ReadonlyMapDeep<KeyType, ValueType>
+				: T extends Readonly<ReadonlySet<infer ItemType>>
+					? ReadonlySetDeep<ItemType>
+					: // Identify tuples to avoid converting them to arrays inadvertently; special case `readonly [...never[]]`, as it emerges undesirably from recursive invocations of ReadonlyDeep below.
+					T extends readonly [] | readonly [...never[]]
+						? readonly []
+						: T extends readonly [infer U, ...infer V]
+							? readonly [ReadonlyDeep<U>, ...ReadonlyDeep<V>]
+							: T extends readonly [...infer U, infer V]
+								? readonly [...ReadonlyDeep<U>, ReadonlyDeep<V>]
+								: T extends ReadonlyArray<infer ItemType>
+									? ReadonlyArray<ReadonlyDeep<ItemType>>
+									: T extends object
+										? ReadonlyObjectDeep<T>
+										: unknown;
 
 /**
 Same as `ReadonlyDeep`, but accepts only `ReadonlyMap`s as inputs. Internal helper for `ReadonlyDeep`.

diff --git a/test-d/readonly-deep.ts b/test-d/readonly-deep.ts
@@ -28,10 +28,15 @@ type ReadonlyJsonValue =
   | boolean
   | null;
 
+class ClassA {
+	foo = 1;
+}
+
 const data = {
 	object: {
 		foo: 'bar',
 	},
+	constructor: ClassA,
 	fn: (_: string) => true,
 	fnWithOverload: ((_: number) => 'foo') as Overloaded,
 	namespace: {} as unknown as Namespace,
@@ -66,6 +71,10 @@ readonlyData.fn('foo');
 readonlyData.fnWithOverload(1);
 readonlyData.fnWithOverload('', 1);
 
+expectType<typeof ClassA>(readonlyData.constructor);
+const instance = new readonlyData.constructor();
+instance.foo = 2; // Constructor is not made readonly
+
 expectError(readonlyData.string = 'bar');
 expectType<{readonly foo: string}>(readonlyData.object);
 expectType<string>(readonlyData.string);