fix(stepper): fix unable update value in async change (#5191)

packages/common/component.ts

@@ -23,6 +23,7 @@ function VantComponent<
   mapKeys(vantOptions, options, {
     data: 'data',
     props: 'properties',
+    watch: 'observers',
     mixins: 'behaviors',
     methods: 'methods',
     beforeCreate: 'created',

packages/definitions/index.ts

@@ -24,6 +24,8 @@ export type VantComponentOptions<
     mixin: string;
   };
 
+  watch?: Record<string, (...args: any[]) => any>;
+
   methods?: Methods;
 
   // lifetimes

packages/stepper/index.ts

@@ -22,7 +22,6 @@ VantComponent({
   props: {
     value: {
       type: null,
-      observer: 'observeValue',
     },
     integer: {
       type: Boolean,
@@ -74,6 +73,12 @@ VantComponent({
     currentValue: '',
   },
 
+  watch: {
+    value() {
+      this.observeValue();
+    },
+  },
+
   created() {
     this.setData({
       currentValue: this.format(this.data.value),
@@ -82,11 +87,8 @@ VantComponent({
 
   methods: {
     observeValue() {
-      const { value, currentValue } = this.data;
-
-      if (!equal(value, currentValue)) {
-        this.setData({ currentValue: this.format(value) });
-      }
+      const { value } = this.data;
+      this.setData({ currentValue: this.format(value) });
     },
 
     check() {