feat: add customRef (#423)

Author: shaonialife

src/apis/state.ts

@@ -5,6 +5,7 @@ export {
   markReactive,
   reactive,
   ref,
+  customRef,
   Ref,
   set,
   shallowReactive,

src/reactivity/index.ts

@@ -9,6 +9,7 @@ export {
 } from './reactive'
 export {
   ref,
+  customRef,
   isRef,
   Ref,
   createRef,

src/reactivity/ref.ts

@@ -128,6 +128,26 @@ export function toRefs<T extends Data = Data>(obj: T): ToRefs<T> {
   return ret
 }
 
+export type CustomRefFactory<T> = (
+  track: () => void,
+  trigger: () => void
+) => {
+  get: () => T
+  set: (value: T) => void
+}
+
+export function customRef<T>(factory: CustomRefFactory<T>): Ref<T> {
+  const version = ref(0)
+  return createRef(
+    factory(
+      () => void version.value,
+      () => {
+        ++version.value
+      }
+    )
+  )
+}
+
 export function toRef<T extends object, K extends keyof T>(
   object: T,
   key: K

test/v3/reactivity/ref.spec.ts

@@ -1,5 +1,6 @@
 import {
   ref,
+  customRef,
   reactive,
   isRef,
   toRef,
@@ -308,34 +309,37 @@ describe('reactivity/ref', () => {
     expect(dummyY).toBe(5)
   })
 
-  // test('customRef', () => {
-  //   let value = 1;
-  //   let _trigger: () => void;
-
-  //   const custom = customRef((track, trigger) => ({
-  //     get() {
-  //       track();
-  //       return value;
-  //     },
-  //     set(newValue: number) {
-  //       value = newValue;
-  //       _trigger = trigger;
-  //     },
-  //   }));
-
-  //   expect(isRef(custom)).toBe(true);
-
-  //   let dummy;
-  //   watchEffect(() => {
-  //     dummy = custom.value;
-  //   }, {flush: 'sync'});
-  //   expect(dummy).toBe(1);
-
-  //   custom.value = 2;
-  //   // should not trigger yet
-  //   expect(dummy).toBe(1);
-
-  //   _trigger!();
-  //   expect(dummy).toBe(2);
-  // });
+  test('customRef', () => {
+    let value = 1
+    let _trigger: () => void
+
+    const custom = customRef((track, trigger) => ({
+      get() {
+        track()
+        return value
+      },
+      set(newValue: number) {
+        value = newValue
+        _trigger = trigger
+      },
+    }))
+
+    expect(isRef(custom)).toBe(true)
+
+    let dummy
+    watchEffect(
+      () => {
+        dummy = custom.value
+      },
+      { flush: 'sync' }
+    )
+    expect(dummy).toBe(1)
+
+    custom.value = 2
+    // should not trigger yet
+    expect(dummy).toBe(1)
+
+    _trigger!()
+    expect(dummy).toBe(2)
+  })
 })