Add no-this-in-template rule. (vuejs#149)

* Add `no-this-in-template` rule.
fixes vuejs#148

* Update documentation

Author: armano2

docs/rules/no-this-in-template.md

@@ -0,0 +1,25 @@
+# Disallow usage of `this` in template. (no-this-in-template)
+
+This rule reports expresions that contain `this` keyword in expressions
+
+## :book: Rule Details
+
+:-1: Examples of **incorrect** code for this rule:
+
+```html
+<template>
+     <a :href="this.link">{{this.text}}</a>
+</template>
+```
+
+:+1: Examples of **correct** code for this rule:
+
+```html
+<template>
+     <a :href="link">{{text}}</a>
+</template>
+```
+
+## :wrench: Options
+
+Nothing.

lib/rules/no-this-in-template.js

@@ -0,0 +1,47 @@
+/**
+ * @fileoverview Disallow usage of `this` in template.
+ * @author Armano
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Disallow usage of `this` in template.',
+      category: 'Best Practices',
+      recommended: false
+    },
+    fixable: null,
+    schema: []
+  },
+
+  /**
+   * Creates AST event handlers for no-this-in-template.
+   *
+   * @param {RuleContext} context - The rule context.
+   * @returns {Object} AST event handlers.
+   */
+  create (context) {
+    utils.registerTemplateBodyVisitor(context, {
+      'VExpressionContainer ThisExpression' (node) {
+        context.report({
+          node,
+          loc: node.loc,
+          message: "Unexpected usage of 'this'."
+        })
+      }
+    })
+
+    return {}
+  }
+}

tests/lib/rules/no-this-in-template.js

@@ -0,0 +1,79 @@
+/**
+ * @fileoverview Disallow usage of `this` in template.
+ * @author Armano
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const rule = require('../../../lib/rules/no-this-in-template')
+
+const RuleTester = require('eslint').RuleTester
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({
+  parser: 'vue-eslint-parser',
+  parserOptions: { ecmaVersion: 2015 }
+})
+
+ruleTester.run('no-this-in-template', rule, {
+  valid: [
+    '',
+    '<template></template>',
+    '<template><div></div></template>',
+    '<template><div>{{ foo.bar }}</div></template>',
+    '<template><div v-for="foo in bar">{{ foo }}</div></template>',
+    '<template><div v-if="foo">{{ foo }}</div></template>',
+    '<template><div :class="foo">{{ foo }}</div></template>',
+    '<template><div :class="{this: foo}">{{ foo }}</div></template>'
+  ],
+  invalid: [
+    {
+      code: '<template><div>{{ this.foo }}</div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    },
+    {
+      code: '<template><div :class="this.foo"></div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    },
+    {
+      code: '<template><div :class="{foo: this.foo}"></div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    },
+    {
+      code: '<template><div :class="{foo: this.foo()}"></div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    },
+    {
+      code: '<template><div v-if="this.foo"></div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    },
+    {
+      code: '<template><div v-for="foo in this.bar"></div></template>',
+      errors: [{
+        message: "Unexpected usage of 'this'.",
+        type: 'ThisExpression'
+      }]
+    }
+  ]
+})