feat(types/reactivity): use DeepReadonly type for readonly return type (#1462)

close #1452

packages/reactivity/src/reactive.ts

@@ -72,9 +72,31 @@ export function shallowReactive<T extends object>(target: T): T {
   )
 }
 
+type Primitive = string | number | boolean | bigint | symbol | undefined | null
+type Builtin = Primitive | Function | Date | Error | RegExp
+type DeepReadonly<T> = T extends Builtin
+  ? T
+  : T extends Map<infer K, infer V>
+    ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>>
+    : T extends ReadonlyMap<infer K, infer V>
+      ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>>
+      : T extends WeakMap<infer K, infer V>
+        ? WeakMap<DeepReadonly<K>, DeepReadonly<V>>
+        : T extends Set<infer U>
+          ? ReadonlySet<DeepReadonly<U>>
+          : T extends ReadonlySet<infer U>
+            ? ReadonlySet<DeepReadonly<U>>
+            : T extends WeakSet<infer U>
+              ? WeakSet<DeepReadonly<U>>
+              : T extends Promise<infer U>
+                ? Promise<DeepReadonly<U>>
+                : T extends {}
+                  ? { readonly [K in keyof T]: DeepReadonly<T[K]> }
+                  : Readonly<T>
+
 export function readonly<T extends object>(
   target: T
-): Readonly<UnwrapNestedRefs<T>> {
+): DeepReadonly<UnwrapNestedRefs<T>> {
   return createReactiveObject(
     target,
     true,