Describe the bug

Extending ESLint config not working.

Environment

 System: OS: macOS 10.14.6 CPU: (4) x64 Intel(R) Core(TM) i7-7660U CPU @ 2.50GHz Binaries: Node: 8.15.0 - ~/.nvm/versions/node/v8.15.0/bin/node Yarn: 1.17.3 - /usr/local/bin/yarn npm: 6.4.1 - ~/.nvm/versions/node/v8.15.0/bin/npm Browsers: Chrome: 76.0.3809.100 Firefox: 67.0 Safari: 12.1.2 npmPackages: react: ^16.9.0 => 16.9.0 react-dom: ^16.9.0 => 16.9.0 react-scripts: 3.1.0 => 3.1.0 npmGlobalPackages: create-react-app: Not Found 

Steps to reproduce

1. yarn create react-app testapp (or npx create-react-app testapp)
2. cd testapp
3. yarn add eslint-config-airbnb (or npm install eslint-config-airbnb)
4. Add the following to package.json:

"eslintConfig": { "extends": [ "react-app", "airbnb"] } 

5. EXTEND_ESLINT=true yarn start ( or EXTEND_ESLINT=true npm start)

Expected behavior

• eslint-config-airbnb should be used
• app should not compile

Actual behavior

• eslint-config-airbnb is not used
• app compiles (it shouldn’t!)

Problem

webpack.config.js checks thateslintConfig.extends exists:

It seems that the property extends never exists on eslintConfig(??)

Deleting the above two lines yields the expected behavior (eslint-config-airbnb is picked up and we see lint errors / Failed to compile message)