Convert scripts/error-codes to use ES6 syntax

scripts/error-codes/__tests__/invertObject-test.js

@@ -6,9 +6,9 @@
  */
 'use strict';
 
-var invertObject = require('../invertObject');
+const invertObject = require('../invertObject');
 
-var objectValues = target => Object.keys(target).map(key => target[key]);
+const objectValues = target => Object.keys(target).map(key => target[key]);
 
 describe('invertObject', () => {
   it('should return an empty object for an empty input', () => {

scripts/error-codes/__tests__/replace-invariant-error-codes-test.js

@@ -17,11 +17,11 @@ function transform(input) {
 }
 
 function compare(input, output) {
-  var compiled = transform(input);
+  const compiled = transform(input);
   expect(compiled).toEqual(output);
 }
 
-var oldEnv;
+let oldEnv;
 
 describe('error codes transform', () => {
   beforeEach(() => {

scripts/error-codes/extract-errors.js

@@ -35,8 +35,8 @@ module.exports = function(opts) {
     );
   }
 
-  var errorMapFilePath = opts.errorMapFilePath;
-  var existingErrorMap;
+  const errorMapFilePath = opts.errorMapFilePath;
+  let existingErrorMap;
   try {
     // Using `fs.readFileSync` instead of `require` here, because `require()`
     // calls are cached, and the cache map is not properly invalidated after
@@ -51,8 +51,8 @@ module.exports = function(opts) {
     existingErrorMap = {};
   }
 
-  var allErrorIDs = Object.keys(existingErrorMap);
-  var currentID;
+  const allErrorIDs = Object.keys(existingErrorMap);
+  let currentID;
 
   if (allErrorIDs.length === 0) {
     // Map is empty
@@ -65,17 +65,17 @@ module.exports = function(opts) {
   existingErrorMap = invertObject(existingErrorMap);
 
   function transform(source) {
-    var ast = babylon.parse(source, babylonOptions);
+    const ast = babylon.parse(source, babylonOptions);
 
     traverse(ast, {
       CallExpression: {
-        exit: function(astPath) {
+        exit(astPath) {
           if (astPath.get('callee').isIdentifier({name: 'invariant'})) {
-            var node = astPath.node;
+            const node = astPath.node;
 
             // error messages can be concatenated (`+`) at runtime, so here's a
             // trivial partial evaluator that interprets the literal value
-            var errorMsgLiteral = evalToString(node.arguments[1]);
+            const errorMsgLiteral = evalToString(node.arguments[1]);
             if (existingErrorMap.hasOwnProperty(errorMsgLiteral)) {
               return;
             }

scripts/error-codes/invertObject.js

@@ -17,12 +17,11 @@
  *   { 0: 'MUCH ERROR', 1: 'SUCH WRONG' }
  */
 function invertObject(targetObj /* : ErrorMap */) /* : ErrorMap */ {
-  var result = {};
-  var mapKeys = Object.keys(targetObj);
+  const result = {};
+  const mapKeys = Object.keys(targetObj);
 
-  for (let i = 0; i < mapKeys.length; i++) {
-    var originalKey = mapKeys[i];
-    var originalVal = targetObj[originalKey];
+  for (const originalKey of mapKeys) {
+    const originalVal = targetObj[originalKey];
 
     result[originalVal] = originalKey;
   }

scripts/error-codes/replace-invariant-error-codes.js

@@ -11,9 +11,9 @@ var evalToString = require('../shared/evalToString');
 var invertObject = require('./invertObject');
 
 module.exports = function(babel) {
-  var t = babel.types;
+  const t = babel.types;
 
-  var SEEN_SYMBOL = Symbol('replace-invariant-error-codes.seen');
+  const SEEN_SYMBOL = Symbol('replace-invariant-error-codes.seen');
 
   // Generate a hygienic identifier
   function getProdInvariantIdentifier(path, file, localState) {
@@ -27,17 +27,17 @@ module.exports = function(babel) {
     return localState.prodInvariantIdentifier;
   }
 
-  var DEV_EXPRESSION = t.identifier('__DEV__');
+  const DEV_EXPRESSION = t.identifier('__DEV__');
 
   return {
-    pre: function() {
+    pre() {
       this.prodInvariantIdentifier = null;
     },
 
     visitor: {
       CallExpression: {
-        exit: function(path, file) {
-          var node = path.node;
+        exit(path, file) {
+          const node = path.node;
           // Ignore if it's already been processed
           if (node[SEEN_SYMBOL]) {
             return;
@@ -74,10 +74,10 @@ module.exports = function(babel) {
             //   - `reactProdInvariant` is always renamed to avoid shadowing
             // The generated code is longer than the original code but will dead
             // code removal in a minifier will strip that out.
-            var condition = node.arguments[0];
-            var errorMsgLiteral = evalToString(node.arguments[1]);
+            const condition = node.arguments[0];
+            const errorMsgLiteral = evalToString(node.arguments[1]);
 
-            var devInvariant = t.callExpression(
+            const devInvariant = t.callExpression(
               node.callee,
               [
                 t.booleanLiteral(false),
@@ -88,22 +88,26 @@ module.exports = function(babel) {
             devInvariant[SEEN_SYMBOL] = true;
 
             // Avoid caching because we write it as we go.
-            var existingErrorMap = JSON.parse(
+            const existingErrorMap = JSON.parse(
               fs.readFileSync(__dirname + '/codes.json', 'utf-8')
             );
-            var errorMap = invertObject(existingErrorMap);
+            const errorMap = invertObject(existingErrorMap);
 
-            var localInvariantId = getProdInvariantIdentifier(path, file, this);
-            var prodErrorId = errorMap[errorMsgLiteral];
-            var body = null;
+            const localInvariantId = getProdInvariantIdentifier(
+              path,
+              file,
+              this
+            );
+            const prodErrorId = errorMap[errorMsgLiteral];
+            let body = null;
 
             if (prodErrorId === undefined) {
               // The error wasn't found in the map.
               // This is only expected to occur on master since we extract codes before releases.
               // Keep the original invariant.
               body = t.expressionStatement(devInvariant);
             } else {
-              var prodInvariant = t.callExpression(
+              const prodInvariant = t.callExpression(
                 localInvariantId,
                 [t.stringLiteral(prodErrorId)].concat(node.arguments.slice(2))
               );