细节修改，保持 dom 结构稳定。

components/form/FormItem.jsx

@@ -22,11 +22,11 @@ class FormItem extends React.Component {
 
   renderHelp() {
     const prefixCls = this.props.prefixCls;
-    return this.props.help ? (
-      <div className={prefixClsFn(prefixCls, 'explain')}>
+    return (
+      <div className={this.props.help ? prefixClsFn(prefixCls, 'explain') : ''}>
         {this.props.help}
       </div>
-    ) : null;
+    );
   }
 
   renderValidateWrapper(children) {
@@ -51,11 +51,11 @@ class FormItem extends React.Component {
 
   renderWrapper(children) {
     const wrapperCol = this.props.wrapperCol;
-    return wrapperCol ? (
+    return (
       <div className={this._getLayoutClass(wrapperCol)}>
         {children}
       </div>
-    ) : children;
+    );
   }
 
   renderLabel() {

components/form/Input.jsx

@@ -43,13 +43,13 @@ class Input extends React.Component {
       </span>
     ) : null;
 
-    return addonBefore || addonAfter ? (
-      <div className={wrapperClassName}>
+    return (
+      <div className={(addonBefore || addonAfter) ? wrapperClassName : ''}>
         {addonBefore}
         {children}
         {addonAfter}
       </div>
-    ) : children;
+    );
   }
 
   renderInput() {

style/mixins/input.less

@@ -152,6 +152,7 @@
   }
 
   // Reset rounded corners
+  > div > .@{inputClass}:first-child,
   > .@{inputClass}:first-child,
   &-addon:first-child {
     border-bottom-right-radius: 0;