From 777b1e440d5c6d45f4277c50c1eb6c622be952ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Wed, 6 Sep 2017 06:15:19 +0800
Subject: [PATCH 1/7] WIP: New: no-unused-vars (fixes #100).

---
 docs/rules/no-unused-vars.md      | 29 ++++++++++
 lib/rules/no-unused-vars.js       | 89 +++++++++++++++++++++++++++++++
 tests/lib/rules/no-unused-vars.js | 47 ++++++++++++++++
 3 files changed, 165 insertions(+)
 create mode 100644 docs/rules/no-unused-vars.md
 create mode 100644 lib/rules/no-unused-vars.js
 create mode 100644 tests/lib/rules/no-unused-vars.js

diff --git a/docs/rules/no-unused-vars.md b/docs/rules/no-unused-vars.md
new file mode 100644
index 000000000..a48f63c33
--- /dev/null
+++ b/docs/rules/no-unused-vars.md
@@ -0,0 +1,29 @@
+# Disallow unused variable definitions of v-for directives or scope attributes. (no-unused-vars)
+
+This rule report variable definitions of v-for directives or scope attributes if those are not used.
+
+## :book: Rule Details
+
+:-1: Examples of **incorrect** code for this rule:
+
+```html
+<template>
+    <ol v-for="i in 5"><!-- "i" is defined but never used. -->
+        <li>item</li>
+    </ol>
+</template>
+```
+
+:+1: Examples of **correct** code for this rule:
+
+```html
+<template>
+    <ol v-for="i in 5">
+        <li>{{i}}</li><!-- "i" is defined and used. -->
+    </ol>
+</template>
+```
+
+## :wrench: Options
+
+Nothing.
diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
new file mode 100644
index 000000000..824acc564
--- /dev/null
+++ b/lib/rules/no-unused-vars.js
@@ -0,0 +1,89 @@
+/**
+ * @fileoverview warn variable definitions of v-for directives or scope attributes if those are not used.
+ * @author 薛定谔的猫<hh_2013@foxmail.com>
+ */
+'use strict'
+
+const utils = require('../utils')
+
+/**
+ * Collect used variables recursively.
+ *
+ * @param {Node} node - The node to collect.
+ * @param {Object} used - The object to restore result.
+ * @returns {Object} used variables.
+ */
+function collectUsed (node, used) {
+  if (node.type === 'VExpressionContainer') {
+    node.references.forEach(ref => {
+      used[ref.id.name] = true
+    })
+  }
+
+  if (node.type === 'VElement') {
+    node.children.forEach(child => collectUsed(child, used))
+  }
+
+  return used
+}
+
+/**
+ * Creates AST event handlers for require-v-for-key.
+ *
+ * @param {RuleContext} context - The rule context.
+ * @returns {Object} AST event handlers.
+ */
+function create (context) {
+  utils.registerTemplateBodyVisitor(context, {
+    "VAttribute[directive=true][key.name='for']": function (node) {
+      const vars = node.value.expression.left
+      const used = collectUsed(node.parent.parent, {})
+
+      // report unused.
+      vars.filter(v => !used[v.name]).forEach(v => {
+        context.report({
+          node,
+          loc: v.loc,
+          message: `'{{name}}' is defined but never used.`,
+          data: {
+            name: v.name
+          }
+        })
+      })
+    },
+
+    "VAttribute[directive=false][key.name='scope']": function (node) {
+      const used = collectUsed(node.parent.parent, {})
+
+      if (!used[node.value.value]) {
+        context.report({
+          node,
+          loc: node.value.loc,
+          message: `'{{name}}' is defined but never used.`,
+          data: {
+            name: node.value.value
+          }
+        })
+      }
+    }
+  })
+
+  return {}
+}
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  create,
+  meta: {
+    docs: {
+      description: 'warn variable definitions of v-for directives or scope attributes if those are not used',
+      category: 'Possible Errors',
+      recommended: false
+    },
+    fixable: null,
+    schema: []
+  }
+}
diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
new file mode 100644
index 000000000..68884eb36
--- /dev/null
+++ b/tests/lib/rules/no-unused-vars.js
@@ -0,0 +1,47 @@
+/**
+ * @author 薛定谔的猫<hh_2013@foxmail.com>
+ * @copyright 2017 薛定谔的猫. All rights reserved.
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/no-unused-vars')
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const tester = new RuleTester({
+  parser: 'vue-eslint-parser',
+  parserOptions: { ecmaVersion: 2015 }
+})
+
+tester.run('no-unused-vars', rule, {
+  valid: [
+    {
+      filename: 'test.vue',
+      code: '<template><ol v-for="i in 5"><li>{{i}}</li></ol></template>'
+    },
+    {
+      filename: 'test.vue',
+      code: '<template scope="props">{{props}}</template>'
+    }
+  ],
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: '<template><ol v-for="i in 5"></ol></template>',
+      errors: ['\'i\' is defined but never used.']
+    },
+    {
+      filename: 'test.vue',
+      code: '<template scope="props"></template>',
+      errors: ['\'props\' is defined but never used.']
+    }
+  ]
+})

From ec2285e58362c68db2eda2216072afcb99c550f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Sun, 17 Sep 2017 02:02:41 +0800
Subject: [PATCH 2/7] Fix: collect used didn't check attrs. & add tests.

---
 lib/rules/no-unused-vars.js       |  5 +++++
 tests/lib/rules/no-unused-vars.js | 12 +++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
index 824acc564..2b5b09b6d 100644
--- a/lib/rules/no-unused-vars.js
+++ b/lib/rules/no-unused-vars.js
@@ -20,8 +20,13 @@ function collectUsed (node, used) {
     })
   }
 
+  if (node.type === 'VAttribute') {
+    collectUsed(node.value, used)
+  }
+
   if (node.type === 'VElement') {
     node.children.forEach(child => collectUsed(child, used))
+    node.startTag.attributes.forEach(attr => collectUsed(attr, used))
   }
 
   return used
diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
index 68884eb36..b7581df92 100644
--- a/tests/lib/rules/no-unused-vars.js
+++ b/tests/lib/rules/no-unused-vars.js
@@ -24,22 +24,24 @@ const tester = new RuleTester({
 tester.run('no-unused-vars', rule, {
   valid: [
     {
-      filename: 'test.vue',
       code: '<template><ol v-for="i in 5"><li>{{i}}</li></ol></template>'
     },
     {
-      filename: 'test.vue',
+      code: '<template><ol v-for="i in 5"><li :prop="i"></li></ol></template>'
+    },
+    {
       code: '<template scope="props">{{props}}</template>'
+    },
+    {
+      code: '<template scope="props"><span v-if="props"></span></template>'
     }
   ],
   invalid: [
     {
-      filename: 'test.vue',
-      code: '<template><ol v-for="i in 5"></ol></template>',
+      code: '<template><ol v-for="i in 5"><li></li></ol></template>',
       errors: ['\'i\' is defined but never used.']
     },
     {
-      filename: 'test.vue',
       code: '<template scope="props"></template>',
       errors: ['\'props\' is defined but never used.']
     }

From c627564e6be5d86468292fbc3700a38830726968 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Sun, 17 Sep 2017 02:07:19 +0800
Subject: [PATCH 3/7] Chore: use optional param to simplify.

---
 lib/rules/no-unused-vars.js | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
index 2b5b09b6d..03dd7c2a3 100644
--- a/lib/rules/no-unused-vars.js
+++ b/lib/rules/no-unused-vars.js
@@ -10,10 +10,12 @@ const utils = require('../utils')
  * Collect used variables recursively.
  *
  * @param {Node} node - The node to collect.
- * @param {Object} used - The object to restore result.
+ * @param {Object} used(optional) - The object to restore result.
  * @returns {Object} used variables.
  */
 function collectUsed (node, used) {
+  used = used || {}
+
   if (node.type === 'VExpressionContainer') {
     node.references.forEach(ref => {
       used[ref.id.name] = true
@@ -42,7 +44,7 @@ function create (context) {
   utils.registerTemplateBodyVisitor(context, {
     "VAttribute[directive=true][key.name='for']": function (node) {
       const vars = node.value.expression.left
-      const used = collectUsed(node.parent.parent, {})
+      const used = collectUsed(node.parent.parent)
 
       // report unused.
       vars.filter(v => !used[v.name]).forEach(v => {
@@ -58,7 +60,7 @@ function create (context) {
     },
 
     "VAttribute[directive=false][key.name='scope']": function (node) {
-      const used = collectUsed(node.parent.parent, {})
+      const used = collectUsed(node.parent.parent)
 
       if (!used[node.value.value]) {
         context.report({

From 6cca458b98cf6ee08c7fd6f4f275b7a25319bbf1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Sun, 17 Sep 2017 06:00:01 +0800
Subject: [PATCH 4/7] use :exit.

---
 lib/rules/no-unused-vars.js | 90 ++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 56 deletions(-)

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
index 03dd7c2a3..1c603b78c 100644
--- a/lib/rules/no-unused-vars.js
+++ b/lib/rules/no-unused-vars.js
@@ -6,34 +6,6 @@
 
 const utils = require('../utils')
 
-/**
- * Collect used variables recursively.
- *
- * @param {Node} node - The node to collect.
- * @param {Object} used(optional) - The object to restore result.
- * @returns {Object} used variables.
- */
-function collectUsed (node, used) {
-  used = used || {}
-
-  if (node.type === 'VExpressionContainer') {
-    node.references.forEach(ref => {
-      used[ref.id.name] = true
-    })
-  }
-
-  if (node.type === 'VAttribute') {
-    collectUsed(node.value, used)
-  }
-
-  if (node.type === 'VElement') {
-    node.children.forEach(child => collectUsed(child, used))
-    node.startTag.attributes.forEach(attr => collectUsed(attr, used))
-  }
-
-  return used
-}
-
 /**
  * Creates AST event handlers for require-v-for-key.
  *
@@ -41,41 +13,47 @@ function collectUsed (node, used) {
  * @returns {Object} AST event handlers.
  */
 function create (context) {
-  utils.registerTemplateBodyVisitor(context, {
-    "VAttribute[directive=true][key.name='for']": function (node) {
-      const vars = node.value.expression.left
-      const used = collectUsed(node.parent.parent)
+  const stack = []
+  let unused = []
 
-      // report unused.
-      vars.filter(v => !used[v.name]).forEach(v => {
-        context.report({
-          node,
-          loc: v.loc,
-          message: `'{{name}}' is defined but never used.`,
-          data: {
-            name: v.name
-          }
+  return utils.defineTemplateBodyVisitor(context, {
+    'VElement:exit' () {
+      unused
+        .forEach((node) => {
+          context.report({
+            node,
+            loc: node.loc,
+            message: `'{{name}}' is defined but never used.`,
+            data: {
+              name: node.name
+            }
+          })
         })
-      })
+      unused = stack.pop()
     },
-
-    "VAttribute[directive=false][key.name='scope']": function (node) {
-      const used = collectUsed(node.parent.parent)
-
-      if (!used[node.value.value]) {
-        context.report({
-          node,
-          loc: node.value.loc,
-          message: `'{{name}}' is defined but never used.`,
-          data: {
-            name: node.value.value
+    VElement (node) {
+      stack.push(unused)
+      unused = []
+      if (node.variables) {
+        for (const variable of node.variables) {
+          unused.push(variable.id)
+        }
+      }
+    },
+    VExpressionContainer (node) {
+      if (node.references) {
+        for (const reference of node.references) {
+          if (reference.mode !== 'w') {
+            const name = reference.id.name
+            unused = unused.filter((el) => el.name !== name)
+            stack.forEach((list, i) => {
+              stack[i] = list.filter((el) => el.name !== name)
+            })
           }
-        })
+        }
       }
     }
   })
-
-  return {}
 }
 
 // ------------------------------------------------------------------------------

From a3651e103f405d643581bcf3a5b1b0d85df6f2a6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Sun, 17 Sep 2017 06:09:45 +0800
Subject: [PATCH 5/7] add tests.

---
 tests/lib/rules/no-unused-vars.js | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
index b7581df92..36f8536d3 100644
--- a/tests/lib/rules/no-unused-vars.js
+++ b/tests/lib/rules/no-unused-vars.js
@@ -29,6 +29,12 @@ tester.run('no-unused-vars', rule, {
     {
       code: '<template><ol v-for="i in 5"><li :prop="i"></li></ol></template>'
     },
+    {
+      code: '<template v-for="i in 5"><comp v-for="j in 10">{{i}}{{j}}</comp></template>'
+    },
+    {
+      code: '<template><ol v-for="i in data"><li v-for="f in i">{{ f.bar.baz }}</li></ol></template>'
+    },
     {
       code: '<template scope="props">{{props}}</template>'
     },
@@ -44,6 +50,14 @@ tester.run('no-unused-vars', rule, {
     {
       code: '<template scope="props"></template>',
       errors: ['\'props\' is defined but never used.']
+    },
+    {
+      code: '<template v-for="i in 5"><comp v-for="j in 10">{{i}}{{i}}</comp></template>',
+      errors: ['\'j\' is defined but never used.']
+    },
+    {
+      code: '<template><ol v-for="i in data"><li v-for="f in i"></li></ol></template>',
+      errors: ['\'f\' is defined but never used.']
     }
   ]
 })

From 4cfaf89457038ec2b8dcd5df700d4a192edf0e98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Mon, 25 Sep 2017 01:01:08 +0800
Subject: [PATCH 6/7] =?UTF-8?q?simplify=20,,=D4=BE=E3=85=82=D4=BE,,?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 lib/rules/no-unused-vars.js | 39 ++++++-------------------------------
 1 file changed, 6 insertions(+), 33 deletions(-)

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
index 1c603b78c..c329aecf8 100644
--- a/lib/rules/no-unused-vars.js
+++ b/lib/rules/no-unused-vars.js
@@ -13,43 +13,16 @@ const utils = require('../utils')
  * @returns {Object} AST event handlers.
  */
 function create (context) {
-  const stack = []
-  let unused = []
-
   return utils.defineTemplateBodyVisitor(context, {
-    'VElement:exit' () {
-      unused
-        .forEach((node) => {
+    VElement (node) {
+      for (const variable of node.variables) {
+        if (variable.references.length === 0) {
           context.report({
-            node,
-            loc: node.loc,
+            node: variable.id,
+            loc: variable.id.loc,
             message: `'{{name}}' is defined but never used.`,
-            data: {
-              name: node.name
-            }
+            data: variable.id
           })
-        })
-      unused = stack.pop()
-    },
-    VElement (node) {
-      stack.push(unused)
-      unused = []
-      if (node.variables) {
-        for (const variable of node.variables) {
-          unused.push(variable.id)
-        }
-      }
-    },
-    VExpressionContainer (node) {
-      if (node.references) {
-        for (const reference of node.references) {
-          if (reference.mode !== 'w') {
-            const name = reference.id.name
-            unused = unused.filter((el) => el.name !== name)
-            stack.forEach((list, i) => {
-              stack[i] = list.filter((el) => el.name !== name)
-            })
-          }
         }
       }
     }

From 7567208a8ae68e8d40c9fbac46de973554f278be Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=96=9B=E5=AE=9A=E8=B0=94=E7=9A=84=E7=8C=AB?=
 <hh_2013@foxmail.com>
Date: Mon, 25 Sep 2017 02:08:49 +0800
Subject: [PATCH 7/7] add tests.

---
 tests/lib/rules/no-unused-vars.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
index 36f8536d3..92812ebcb 100644
--- a/tests/lib/rules/no-unused-vars.js
+++ b/tests/lib/rules/no-unused-vars.js
@@ -58,6 +58,10 @@ tester.run('no-unused-vars', rule, {
     {
       code: '<template><ol v-for="i in data"><li v-for="f in i"></li></ol></template>',
       errors: ['\'f\' is defined but never used.']
+    },
+    {
+      code: '<template><div v-for="(v, i, c) in foo"></div></template>',
+      errors: ['\'v\' is defined but never used.', '\'i\' is defined but never used.', '\'c\' is defined but never used.']
     }
   ]
 })