fix(customReactive): avoid circular reference.

src/mixin.ts

@@ -149,7 +149,8 @@ export function mixin(Vue: VueConstructor) {
     }
   }
 
-  function customReactive(target: object) {
+  function customReactive(target: object, visited = new Set()) {
+    if (visited.has(target)) return
     if (
       !isPlainObject(target) ||
       isRef(target) ||
@@ -165,7 +166,8 @@ export function mixin(Vue: VueConstructor) {
       const val = target[k]
       defineReactive(target, k, val)
       if (val) {
-        customReactive(val)
+        visited.add(val)
+        customReactive(val, visited)
       }
       return
     })

test/setupContext.spec.ts

@@ -5,9 +5,12 @@ import {
   ref,
   nextTick,
   SetupContext,
+  getCurrentInstance,
 } from '../src'
+import { mockWarn } from './helpers'
 
 describe('setupContext', () => {
+  mockWarn(true)
   it('should have proper properties', () => {
     let context: SetupContext = undefined!
 
@@ -195,4 +198,31 @@ describe('setupContext', () => {
 
     expect(_attrs.foo).toBe('bar2')
   })
+
+  // #563
+  it('should not RangeError: Maximum call stack size exceeded', async () => {
+    createApp(
+      defineComponent({
+        template: `<div/>`,
+        setup() {
+          // @ts-expect-error
+          const app = getCurrentInstance().proxy
+          let mockNT: any = []
+          mockNT.__ob__ = {}
+          const test = {
+            app,
+            mockNT,
+          }
+          return {
+            test,
+          }
+        },
+      })
+    ).mount()
+
+    await nextTick()
+    expect(
+      `"RangeError: Maximum call stack size exceeded"`
+    ).not.toHaveBeenWarned()
+  })
 })