fix(Field): incorrect maxlength slicing (#7284)

* fix(Field): incorrect maxlength slicing

* chore: robust

src/field/index.js

@@ -294,10 +294,15 @@ export default createComponent({
     updateValue(value, trigger = 'onChange') {
       value = isDef(value) ? String(value) : '';
 
-      // native maxlength not work when type is number
+      // native maxlength have incorrect line-break counting
+      // see: https://github.com/youzan/vant/issues/5033
       const { maxlength } = this;
       if (isDef(maxlength) && value.length > maxlength) {
-        value = value.slice(0, maxlength);
+        if (this.value && this.value.length === +maxlength) {
+          ({ value } = this);
+        } else {
+          value = value.slice(0, maxlength);
+        }
       }
 
       if (this.type === 'number' || this.type === 'digit') {

src/field/test/index.spec.js

@@ -171,17 +171,25 @@ test('maxlength', async () => {
       value: 1234,
       type: 'number',
     },
+    listeners: {
+      input(value) {
+        wrapper && wrapper.setProps({ value });
+      },
+    },
   });
 
   const input = wrapper.find('input');
   expect(input.element.value).toEqual('123');
 
   input.element.value = 1234;
-  await later();
   input.trigger('input');
-
   expect(input.element.value).toEqual('123');
   expect(wrapper.emitted('input')[0][0]).toEqual('123');
+
+  // see: https://github.com/youzan/vant/issues/7265
+  input.element.value = 1423;
+  input.trigger('input');
+  expect(input.element.value).toEqual('123');
 });
 
 test('clearable prop', () => {