修复effect不可嵌套问题

src/reactivity/__tests__/effect.spec.ts

@@ -116,4 +116,33 @@ describe("effect", () => {
     stop(runner);
     expect(onStop).toHaveBeenCalled();
   });
+
+  it('nested effect', () => {
+    const obj = reactive({ foo: 1, bar: 1 })
+    let temp1, temp2
+    const outerCall = jest.fn()
+    const innerCall = jest.fn()
+    effect(() => {
+      outerCall()
+      effect(() => {
+        innerCall()
+        temp2 = obj.bar
+      })
+      temp1 = obj.foo
+    })
+    // 两个都会执行
+    expect(outerCall).toBeCalledTimes(1)
+    expect(innerCall).toBeCalledTimes(1)
+
+    obj.bar = 2
+    // 只执行内层的
+    expect(outerCall).toBeCalledTimes(1)
+    expect(innerCall).toBeCalledTimes(2)
+
+    obj.foo = 2
+    // 内外层都执行
+    expect(outerCall).toBeCalledTimes(2)
+    expect(innerCall).toBeCalledTimes(3)
+
+  })
 });

src/reactivity/src/effect.ts

@@ -4,6 +4,7 @@ import { extend } from "../../shared/index";
 let activeEffect = void 0;
 let shouldTrack = false;
 const targetMap = new WeakMap();
+const effectStack: any[] = []
 
 // 用于依赖收集
 export class ReactiveEffect {
@@ -34,12 +35,16 @@ export class ReactiveEffect {
     // 执行的时候给全局的 activeEffect 赋值
     // 利用全局属性来获取当前的 effect
     activeEffect = this as any;
+    effectStack.push(this)
     // 执行用户传入的 fn
     console.log("执行用户传入的 fn");
     const result = this.fn();
+    effectStack.pop()
+    activeEffect = effectStack[effectStack.length - 1]
     // 重置
-    shouldTrack = false;
-    activeEffect = undefined;
+    if (effectStack.length === 0) {
+      shouldTrack = false
+    }
 
     return result;
   }