Added babel/no-invalid-this rule. (Closes babel#12)

Author: mathieumg

README.md

@@ -34,7 +34,8 @@ original ones as well!).
     "babel/arrow-parens": 1,
     "babel/no-await-in-loop": 1,
     "babel/flow-object-type": 1,
-    "babel/func-params-comma-dangle": 1
+    "babel/func-params-comma-dangle": 1,
+    "babel/no-invalid-this": 1
   }
 }
 ```
@@ -50,6 +51,7 @@ Each rule corresponds to a core `eslint` rule, and has the same options.
 - `babel/object-curly-spacing`: doesn't complain about `export x from "mod";` or `export * as x from "mod";` (🛠 )
 - `babel/object-shorthand`: doesn't fail when using object spread (`...obj`)
 - `babel/arrow-parens`: Handles async functions correctly (🛠 )
+- `babel/no-invalid-this`: doesn't fail when inside class properties (`class A { a = this.b; }`)
 
 The following rules are not in `eslint`, but are relevant only to syntax that is not specified by
 the current JavaScript standard or supported by `eslint`.

package.json

@@ -29,6 +29,7 @@
   "devDependencies": {
     "babel-eslint": "^6.1.0",
     "eslint": "^3.0.0",
+    "lodash.clonedeep": "^4.5.0",
     "mocha": "^3.0.0"
   }
 }

rules/no-invalid-this.js

@@ -30,6 +30,8 @@ module.exports = {
         const stack = [],
             sourceCode = context.getSourceCode();
 
+        let insideClassProperty = false;
+
         /**
          * Gets the current checking context.
          *
@@ -51,6 +53,23 @@ module.exports = {
             return current;
         };
 
+        /**
+         * `this` should be fair game anywhere inside a class property.
+         *
+         * @returns {void}
+         */
+        function enterClassProperty() {
+            insideClassProperty = true;
+        }
+
+        /**
+         * Back to the normal check.
+         * @returns {void}
+         */
+        function exitClassProperty() {
+            insideClassProperty = false;
+        }
+
         /**
          * Pushs new checking context into the stack.
          *
@@ -104,6 +123,8 @@ module.exports = {
                 stack.pop();
             },
 
+            ClassProperty: enterClassProperty,
+            "ClassProperty:exit": exitClassProperty,
             FunctionDeclaration: enterFunction,
             "FunctionDeclaration:exit": exitFunction,
             FunctionExpression: enterFunction,
@@ -113,7 +134,7 @@ module.exports = {
             ThisExpression(node) {
                 const current = stack.getCurrent();
 
-                if (current && !current.valid) {
+                if (!insideClassProperty && current && !current.valid) {
                     context.report(node, "Unexpected 'this'.");
                 }
             }

tests/rules/no-invalid-this.js

@@ -9,7 +9,7 @@
 // Requirements
 //------------------------------------------------------------------------------
 
-const lodash = require("lodash");
+const cloneDeep = require("lodash.clonedeep");
 const rule = require("../../rules/no-invalid-this");
 const RuleTester = require("../RuleTester");
 
@@ -68,7 +68,7 @@ function extractPatterns(patterns, type) {
     // Clone and apply the pattern environment.
     const patternsList = patterns.map(function(pattern) {
         return pattern[type].map(function(applyCondition) {
-            const thisPattern = lodash.cloneDeep(pattern);
+            const thisPattern = cloneDeep(pattern);
 
             applyCondition(thisPattern);
 
@@ -582,6 +582,23 @@ const patterns = [
         valid: [NORMAL],
         invalid: [USE_STRICT, IMPLIED_STRICT, MODULES]
     },
+
+    // babel/no-invalid-this
+
+    // Class Instance Properties.
+    {
+        code: "class A {a = this.b;};",
+        parserOptions: { ecmaVersion: 6 },
+        valid: [NORMAL, USE_STRICT, IMPLIED_STRICT, MODULES],
+        invalid: []
+    },
+
+    {
+        code: "class A {a = () => {return this.b;};};",
+        parserOptions: { ecmaVersion: 6 },
+        valid: [NORMAL, USE_STRICT, IMPLIED_STRICT, MODULES],
+        invalid: []
+    },
 ];
 
 const ruleTester = new RuleTester();