Describe the bug

When a project has an invalid .eslintrc.js and is started with EXTEND_ESLINT=true create-react-app will fail to compile.

Did you try recovering your dependencies?

Not sure if applicable since this happens in a newly generated project too.

Which terms did you search for in User Guide?

I mostly looked at which does not mention existing .eslintrc.js https://create-react-app.dev/docs/setting-up-your-editor#displaying-lint-output-in-the-editor

Environment

Environment Info:

  System:
    OS: macOS 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
  Binaries:
    Node: 8.15.0 - ~/.asdf/shims/node
    Yarn: 1.17.3 - /usr/local/bin/yarn
    npm: 6.4.1 - ~/.asdf/shims/npm
  Browsers:
    Chrome: Not Found
    Firefox: 68.0.2
    Safari: Not Found
  npmPackages:
    react: ^16.9.0 => 16.9.0
    react-dom: ^16.9.0 => 16.9.0
    react-scripts: 3.1.1 => 3.1.1
  npmGlobalPackages:
    create-react-app: Not Found

Steps to reproduce

1. npx create-react-app eslint-test
2. cd eslint-test
3. touch .eslintrc.js (or .eslintrc.json, .eslintrc.yml)
4. EXTEND_ESLINT=true yarn start

Note that in step 3 the contents of eslintrc doesn't matter. A valid eslintrc will also fail.
Edit: This is a bit more nuanced. The following works:

module.exports = {
}

This does not:

module.exports = {
  extends: 'eslint:recommended',
}

but this does:

module.exports = {
  extends: ['react-app', 'eslint:recommended']
}

Expected behavior

The server to start
Edit: I expect to see an error about an invalid eslintrc. Perhaps suggesting that react-app needs to be extended.

Actual behavior

Compile errors like

./src/serviceWorker.js
  Line 13:  Parsing error: The keyword 'const' is reserved

Reproducible demo

https://github.com/klaaspieter/create-react-app-eslintrc

Steps to reproduce:

1. git clone https://github.com/klaaspieter/create-react-app-eslintrc.git
2. cd create-react-app-eslintrc
3. yarn (Note that yarn.lock changes, is this a separate issue?)
4. EXTEND_ESLINT=true yarn start