From ae9b2c675046c224d0efa1eb7127cc00ca5b9895 Mon Sep 17 00:00:00 2001
From: Weijia Wang <381152119@qq.com>
Date: Tue, 31 Oct 2017 23:51:59 +0800
Subject: [PATCH] tools: Implement automatic fix for no-let-in-for-declaration

Refs: https://github.com/nodejs/node/issues/16636
---
 .../test-eslint-no-let-in-for-declaration.js     |  3 +++
 tools/eslint-rules/no-let-in-for-declaration.js  | 16 +++++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/test/parallel/test-eslint-no-let-in-for-declaration.js b/test/parallel/test-eslint-no-let-in-for-declaration.js
index b6b7c357455ab9..c3c1e17a729252 100644
--- a/test/parallel/test-eslint-no-let-in-for-declaration.js
+++ b/test/parallel/test-eslint-no-let-in-for-declaration.js
@@ -24,14 +24,17 @@ ruleTester.run('no-let-in-for-declaration', rule, {
   invalid: [
     {
       code: 'for (let foo = 1;;);',
+      output: 'for (var foo = 1;;);',
       errors: [{ message }]
     },
     {
       code: 'for (let foo in bar);',
+      output: 'for (var foo in bar);',
       errors: [{ message }]
     },
     {
       code: 'for (let foo of bar);',
+      output: 'for (var foo of bar);',
       errors: [{ message }]
     }
   ]
diff --git a/tools/eslint-rules/no-let-in-for-declaration.js b/tools/eslint-rules/no-let-in-for-declaration.js
index 8b1a6783e0773d..34ad2d5761fda2 100644
--- a/tools/eslint-rules/no-let-in-for-declaration.js
+++ b/tools/eslint-rules/no-let-in-for-declaration.js
@@ -14,7 +14,7 @@
 
 module.exports = {
   create(context) {
-
+    const sourceCode = context.getSourceCode();
     const msg = 'Use of `let` as the loop variable in a for-loop is ' +
                 'not recommended. Please use `var` instead.';
 
@@ -23,7 +23,12 @@ module.exports = {
      */
     function testForLoop(node) {
       if (node.init && node.init.kind === 'let') {
-        context.report(node.init, msg);
+        context.report({
+          node: node.init,
+          message: msg,
+          fix: (fixer) =>
+            fixer.replaceText(sourceCode.getFirstToken(node.init), 'var')
+        });
       }
     }
 
@@ -33,7 +38,12 @@ module.exports = {
      */
     function testForInOfLoop(node) {
       if (node.left && node.left.kind === 'let') {
-        context.report(node.left, msg);
+        context.report({
+          node: node.left,
+          message: msg,
+          fix: (fixer) =>
+            fixer.replaceText(sourceCode.getFirstToken(node.left), 'var')
+        });
       }
     }