Cannot read property 'ecmaFeatures' of undefined

Getting

Parsing error: Cannot read property 'ecmaFeatures' of undefined

Tell us about your environment

• ESLint Version: 5.1.0
• Node Version: 10.6.0
• **npm Version:**6.1.0"

my eslintrc

env:
  node: true
  es6: true
  jquery: false
  browser: false

extends:
  - eslint:recommended

rules:
  curly: off

[not-an-aardvark]

The root cause of this issue is that two different versions of espree are being loaded simultaneously with the same version of acorn. espree works by adding a plugin to the acorn parser, and acorn’s plugin API seems to require setting global state on the acorn object. As a result, espree@4 is setting some state by adding listeners to acorn, and then espree@3 is getting loaded and is overriding the state that was set by espree@4. This is causing espree@3’s listeners to unexpectedly get called even though the running version of ESLint is using espree@4, which is causing espree@3 to throw an error.

To me, it seems like the best way to fix this would be for acorn to allow registering a plugin without modifying global state on the acorn package. Another possibility would be for espree to include acorn as a bundled dependency to ensure that it never shares its version of acorn with any other packages.

[regseb]

@not-an-aardvark This bug comes when eslint@5 and eslint@4 are used in project. It’s not specific at standard (https://github.com/xojs/xo/issues/336 and https://github.com/javascript-obfuscator/webpack-obfuscator/issues/35).

A test case with only ESLint:

• package.json:

{
    "dependencies": {
        "eslint": "5.2.0",
        "other": "file:./other"
    }
}

• testcase.js:

#!/usr/bin/env node

var Linter = require("eslint").Linter;
require("other"); // Comment me !
var linter = new Linter();

var messages = linter.verify("var foo;", {
    rules: {
        semi: 2
    }
}, { filename: "foo.js" });

console.log(messages);

• other/package.json:

{
    "name": "other",
    "main": "index",
    "dependencies": {
        "eslint": "4.19.1"
    }
}

• other/index.js:

require("eslint");

To test, decompress testcase.tar.gz. Execute npm install and ./testcase.js. This JSON is displayed in console:

[ { ruleId: null,
    fatal: true,
    severity: 2,
    message:
     'Parsing error: Cannot read property \'ecmaFeatures\' of undefined',
    line: undefined,
    column: undefined } ]

If you comment line 4 of testcase.js (require("other");), the output is:

[]