Change parser from Esprima to Babel

This commit changes the parser from esprima (the default parser that comes with recast) to @babel/parser. It uses the pre-configured Babel parser shipped with recast (recast/parsers/babel) that ensures the AST returned by Babel is compatible with recast.

The goal of this change is to support newer JavaScript syntax that is not yet supported by Esprima, so this commit also includes a new test where the input source includes class syntax, class fields, and a decorator.

I also replaced jshint with eslint, based on the current ember-cli configuration, but adjusted the rules to be looser to avoid noise in the diff. We can tighten up the rules and update the source in a separate change.

This also adds a prettier config pulled from ember-cli, but does not enforce the rules in the test suite at this time (again, to avoid a noisy diff making it hard to understand the Babel/Esprima parser change).

.eslintignore

@@ -0,0 +1 @@
+/tests/fixtures/

.eslintrc.js

@@ -0,0 +1,67 @@
+module.exports = {
+  root: true,
+  parserOptions: {
+    ecmaVersion: 2018,
+  },
+  plugins: ['mocha', 'node'],
+  extends: ['eslint:recommended', 'plugin:node/recommended', 'prettier'],
+  env: {
+    browser: false,
+    node: true,
+    es6: true,
+  },
+  globals: {},
+  rules: {
+    /*** For compatibility with existing source */
+    'no-var': 0,
+    'no-undef': 0,
+    'strict': 0,
+    'object-shorthand': 0,
+    'no-lonely-if': 0,
+
+    /*** Possible Errors ***/
+
+    'no-console': 0,
+    'no-template-curly-in-string': 2,
+    'no-unsafe-negation': 2,
+
+    /*** Best Practices ***/
+
+    curly: 2,
+    eqeqeq: 2,
+    'guard-for-in': 0,
+    'no-caller': 2,
+    'no-eq-null': 2,
+    'no-eval': 2,
+    'no-new': 0,
+    'no-unused-expressions': [
+      2,
+      {
+        allowShortCircuit: true,
+        allowTernary: true,
+      },
+    ],
+    'wrap-iife': 0,
+    yoda: 2,
+
+    /*** Variables ***/
+
+    'no-unused-vars': 2,
+    'no-use-before-define': [2, 'nofunc'],
+
+    /*** Stylistic Issues ***/
+
+    camelcase: 2,
+    'new-cap': [2, { properties: false }],
+    'no-array-constructor': 2,
+    'no-bitwise': 2,
+    'no-plusplus': 0,
+    'no-unneeded-ternary': 2,
+
+    /*** ECMAScript 6 ***/
+
+    'no-useless-computed-key': 2,
+    'prefer-template': 2,
+    'symbol-description': 2,
+  },
+};

.prettierrc.js

@@ -0,0 +1,7 @@
+'use strict';
+
+module.exports = {
+  singleQuote: true,
+  trailingComma: 'es5',
+  printWidth: 120,
+};

lib/ember-router-generator.js

@@ -1,6 +1,7 @@
 module.exports = EmberRouterGenerator;
 
 var recast = require('recast');
+var parser = require('recast/parsers/babel');
 
 var findFunctionExpression = require('./helpers/find-function-expression');
 var findRoutes = require('./helpers/find-routes');
@@ -21,7 +22,7 @@ EmberRouterGenerator.prototype.clone = function() {
 };
 
 EmberRouterGenerator.prototype._ast  = function() {
-  return (this.ast = this.ast || recast.parse(this.source));
+  return (this.ast = this.ast || recast.parse(this.source, { parser }));
 };
 
 EmberRouterGenerator.prototype._walk  = function() {

package.json

@@ -19,14 +19,20 @@
     "url": "https://github.com/ember-cli/ember-router-generator.git"
   },
   "dependencies": {
+    "@babel/parser": "^7.4.5",
+    "@babel/traverse": "^7.4.5",
     "recast": "^0.18.1"
   },
   "devDependencies": {
     "assertion-error": "^1.1.0",
     "chai": "^4.2.0",
-    "esprima": "^2.7.2",
+    "eslint": "^6.0.1",
+    "eslint-config-prettier": "^6.0.0",
+    "eslint-plugin-mocha": "^5.3.0",
+    "eslint-plugin-node": "^9.1.0",
     "mocha": "^6.1.4",
-    "mocha-jshint": "2.3.1"
+    "mocha-eslint": "^5.0.0",
+    "prettier": "^1.18.2"
   },
   "author": "Adolfo Builes",
   "license": "MIT",

tests/fixtures/class-syntax-foos-route.js

@@ -0,0 +1,8 @@
+class AppRouter extends Router {
+  @tracked location = config.locationType;
+  rootURL = config.rootURL;
+}
+
+Router.map(function() {
+  this.route('foos');
+});

tests/fixtures/class-syntax.js

@@ -0,0 +1,7 @@
+class AppRouter extends Router {
+  @tracked location = config.locationType;
+  rootURL = config.rootURL;
+}
+
+Router.map(function() {
+});

tests/generator-test.js

@@ -1,10 +1,6 @@
 var EmberRouterGenerator = require('../index.js');
-var assert = require('assert');
 var fs = require('fs');
-var astEquality = require('./helpers/esprima-ast-equality');
-var recast = require('recast');
-var expect = require('chai').expect;
-
+var astEquality = require('./helpers/ast-equality');
 
 describe('Adding routes', function() {
   it('adds routes', function() {
@@ -16,6 +12,15 @@ describe('Adding routes', function() {
     astEquality(newRoutes.code(), fs.readFileSync('./tests/fixtures/foos-route.js'));
   });
 
+  it('handles files with class syntax', function() {
+    var source = fs.readFileSync('./tests/fixtures/class-syntax.js');
+
+    var routes = new EmberRouterGenerator(source);
+    var newRoutes = routes.add('foos');
+
+    astEquality(newRoutes.code(), fs.readFileSync('./tests/fixtures/class-syntax-foos-route.js'));
+  });
+
   it('leaves untouched existing routes', function() {
     var source = fs.readFileSync('./tests/fixtures/foos-route.js');
 

tests/helpers/esprima-ast-equality.js → tests/helpers/ast-equality.js

@@ -10,13 +10,16 @@ EqualityError.prototype = Object.create(Error.prototype);
 EqualityError.prototype.name = 'EqualityError';
 EqualityError.prototype.constructor = EqualityError;
 
-var assert = require('assert');
-var esprima = require('esprima');
 var recast = require('recast');
+var parser = require('recast/parsers/babel');
+var traverse = require('@babel/traverse').default;
 
 module.exports = function(actual, expected, message) {
-  var parsedActual   = esprima.parse(actual);
-  var parsedExpected = esprima.parse(expected);
+  var parsedActual   = recast.parse(actual.toString(), { parser });
+  var parsedExpected = recast.parse(expected.toString(), { parser });
+
+  // Removes source-specific metadata from AST nodes
+  stripSourceInfo(parsedActual, parsedExpected);
 
   var seemEqual = JSON.stringify(parsedActual) === JSON.stringify(parsedExpected);
 
@@ -27,3 +30,15 @@ module.exports = function(actual, expected, message) {
     );
   }
 };
+
+function stripSourceInfo(ast1, ast2) {
+  const stripNode = node => {
+    delete node.tokens;
+    delete node.loc;
+    delete node.start;
+    delete node.end;
+  }
+
+  traverse.cheap(ast1, stripNode);
+  traverse.cheap(ast2, stripNode);
+}

tests/jshint-test.js

@@ -1 +1 @@
-require('mocha-jshint')();
+require('mocha-eslint')(['lib', 'index.js', 'tests/*.js', 'tests/helpers']);