polish template v-for error report

Fix vuejs#164, don't report error when nested v-for refers iterator.
Do report error when nested v-for doesn't refer iterator.

Author: HerringtonDarkholme

lib/rules/valid-v-for.js

@@ -19,34 +19,50 @@ const utils = require('../utils')
  * Check whether the given attribute is using the variables which are defined by `v-for` directives.
  * @param {ASTNode} vFor The attribute node of `v-for` to check.
  * @param {ASTNode} vBindKey The attribute node of `v-bind:key` to check.
+ * @param {boolean} isChild If checks on child in template[v-for].
  * @returns {boolean} `true` if the node is using the variables which are defined by `v-for` directives.
  */
-function isUsingIterationVar (vFor, vBindKey) {
+function isUsingIterationVar (vFor, vBindKey, isChild) {
   if (vBindKey.value == null) {
     return false
   }
   const references = vBindKey.value.references
   const variables = vFor.parent.parent.variables
-
-  return references.some(reference =>
+  const used = references.some(reference =>
         variables.some(variable =>
             variable.id.name === reference.id.name &&
             variable.kind === 'v-for'
         )
     )
+
+  if (!isChild || used) {
+    return used
+  }
+  const childFor = utils.getDirective(vBindKey.parent.parent, 'for')
+  if (!childFor) {
+    return false
+  }
+  const childForRefs = childFor.value.references
+  return childForRefs.some(cref =>
+         variables.some(variable =>
+             cref.id.name === variable.id.name &&
+             variable.kind === 'v-for'
+         )
+    )
 }
 
 /**
  * Check the given element about `v-bind:key` attributes.
  * @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} isChild If element is a child of template[v-for].
  */
-function checkKey (context, vFor, element) {
+function checkKey (context, vFor, element, isChild) {
   if (element.name === 'template') {
     for (const child of element.children) {
       if (child.type === 'VElement') {
-        checkKey(context, vFor, child)
+        checkKey(context, vFor, child, true)
       }
     }
     return
@@ -61,7 +77,7 @@ function checkKey (context, vFor, element) {
       message: "Custom elements in iteration require 'v-bind:key' directives."
     })
   }
-  if (vBindKey != null && !isUsingIterationVar(vFor, vBindKey)) {
+  if (vBindKey != null && !isUsingIterationVar(vFor, vBindKey, isChild)) {
     context.report({
       node: vBindKey,
       loc: vBindKey.loc,

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><div><template v-for="x of list"><div v-for="foo of x" :key="foo"></div></template></div></template>'
     }
   ],
   invalid: [
@@ -179,6 +183,11 @@ tester.run('valid-v-for', rule, {
       filename: 'test.vue',
       code: '<template><div><template v-for="xin list"><div></div></template></div></template>',
       errors: ["'v-for' directives require that attribute value."]
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div><template v-for="x of list"><div v-for="foo of y" :key="foo"></div></template></div></template>',
+      errors: ["Expected 'v-bind:key' directive to use the variables which are defined by the 'v-for' directive."]
     }
   ]
 })