fix invalid report from template(v-for) > div(v-for)

fixes vuejs#164 vuejs/vetur#400

Author: armano2

lib/rules/valid-v-for.js

@@ -41,17 +41,22 @@ function isUsingIterationVar (vFor, vBindKey) {
  * @param {RuleContext} context The rule context to report.
  * @param {ASTNode} vFor The attribute node of `v-for` to check.
  * @param {ASTNode} element The element node to check.
+ * @param {boolean} child Are we working on child element.
  */
-function checkKey (context, vFor, element) {
+function checkKey (context, vFor, element, child) {
   if (element.name === 'template') {
     for (const child of element.children) {
       if (child.type === 'VElement') {
-        checkKey(context, vFor, child)
+        checkKey(context, vFor, child, true)
       }
     }
     return
   }
 
+  if (child && utils.hasDirective(element, 'for')) { // template(v-for) > div(v-for)
+    return
+  }
+
   const vBindKey = utils.getDirective(element, 'bind', 'key')
 
   if (utils.isCustomComponent(element) && vBindKey == null) {
@@ -83,7 +88,7 @@ function create (context) {
     "VAttribute[directive=true][key.name='for']" (node) {
       const element = node.parent.parent
 
-      checkKey(context, node, element)
+      checkKey(context, node, element, false)
 
       if (node.key.argument) {
         context.report({

tests/lib/rules/valid-v-for.js

@@ -82,6 +82,10 @@ tester.run('valid-v-for', rule, {
     {
       filename: 'test.vue',
       code: '<template v-for="x of list">foo<div></div></template>'
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><template v-for="x of list"><div v-for="foo of x" :key="foo"></div></template></template>'
     }
   ],
   invalid: [