feat(Form): add validate-trigger prop

src/form/README.md

@@ -411,6 +411,7 @@ export default {
 | error-message-align | Error message align, can be set to `center` `right` | *string* | `left` |
 | colon | Whether to display `:` after label | *boolean* | *false* |
 | validate-first | Whether to stop the validation when a rule fails | *boolean* | `false` |
+| validate-trigger `v2.5.2` | When to validate the form，can be set to `onChange`、`onSubmit` | *string* | `onBlur` |
 
 ### Events
 

src/form/README.zh-CN.md

@@ -443,6 +443,7 @@ export default {
 | error-message-align | 错误提示文案对齐方式，可选值为 `center` `right` | *string* | `left` |
 | colon | 是否在 label 后面添加冒号 | *boolean* | *false* |
 | validate-first | 是否在某一项校验不通过时停止校验 | *boolean* | `false` |
+| validate-trigger `v2.5.2` | 表单校验触发时机，可选值为`onChange`、`onSubmit` | *string* | `onBlur` |
 
 > 表单项的 API 参见：[Field 组件](#/zh-CN/field#api)
 

src/form/index.js

@@ -10,6 +10,10 @@ export default createComponent({
     inputAlign: String,
     validateFirst: Boolean,
     errorMessageAlign: String,
+    validateTrigger: {
+      type: String,
+      default: 'onBlur',
+    },
   },
 
   provide() {

src/form/test/props.spec.js

@@ -1,3 +1,4 @@
+import { later } from '../../../test';
 import { mountForm, submitForm, getSimpleRules } from './shared';
 
 test('rules prop - execute order', async () => {
@@ -167,3 +168,54 @@ test('error-message-align prop', () => {
   });
   expect(wrapper).toMatchSnapshot();
 });
+
+test('validate-trigger - onBlur', async () => {
+  const wrapper = mountForm({
+    template: `
+      <van-form ref="form">
+        <van-field name="A" :rules="rulesA" value="" />
+      </van-form>
+    `,
+    data: getSimpleRules,
+  });
+
+  const input = wrapper.find('input');
+
+  input.trigger('input');
+  await later();
+  expect(wrapper.contains('.van-field__error-message')).toBeFalsy();
+
+  input.trigger('blur');
+  await later();
+  expect(wrapper.contains('.van-field__error-message')).toBeTruthy();
+});
+
+test('validate-trigger - onChange', async () => {
+  const wrapper = mountForm({
+    template: `
+      <van-form validate-trigger="onChange" ref="form">
+        <van-field v-model="value" name="A" :rules="rulesA" />
+      </van-form>
+    `,
+    data() {
+      return {
+        ...getSimpleRules(),
+        value: '',
+      };
+    },
+  });
+
+  const input = wrapper.find('input');
+
+  input.trigger('blur');
+  await later();
+  expect(wrapper.contains('.van-field__error-message')).toBeFalsy();
+
+  wrapper.setData({ value: '1' });
+  await later();
+  expect(wrapper.contains('.van-field__error-message')).toBeFalsy();
+
+  wrapper.setData({ value: '' });
+  await later();
+  expect(wrapper.contains('.van-field__error-message')).toBeTruthy();
+});