feat(Form): add validate-first prop

src/form/index.js

@@ -3,6 +3,10 @@ import { createNamespace } from '../utils';
 const [createComponent, bem] = createNamespace('form');
 
 export default createComponent({
+  props: {
+    validateFirst: Boolean,
+  },
+
   provide() {
     return {
       vanForm: this,
@@ -16,8 +20,35 @@ export default createComponent({
   },
 
   methods: {
-    // @exposed-api
-    validate() {
+    validateSeq() {
+      return new Promise((resolve, reject) => {
+        const errors = [];
+
+        this.fields
+          .reduce(
+            (promise, field) =>
+              promise.then(() => {
+                if (!errors.length) {
+                  return field.validate().then(error => {
+                    if (error) {
+                      errors.push(error);
+                    }
+                  });
+                }
+              }),
+            Promise.resolve()
+          )
+          .then(() => {
+            if (errors.length) {
+              reject(errors);
+            } else {
+              resolve();
+            }
+          });
+      });
+    },
+
+    validateAll() {
       return new Promise((resolve, reject) => {
         Promise.all(this.fields.map(item => item.validate())).then(errors => {
           errors = errors.filter(item => item);
@@ -31,6 +62,11 @@ export default createComponent({
       });
     },
 
+    // @exposed-api
+    validate() {
+      return this.validateFirst ? this.validateSeq() : this.validateAll();
+    },
+
     getValues() {
       return this.fields.reduce((form, field) => {
         form[field.name] = field.formValue;