When I want to use parameter EXTEND_ESLINT=true in .env then I got an error.
it's happening because paths.appIndexJs is undefined, you can see how it used in config/webpack.config.js:403
TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
...
at module.exports (.../node_modules/universal-react-scripts/config/webpack.config.js:415:19)
When I want to use parameter
EXTEND_ESLINT=true
in.env
then I got an error. it's happening becausepaths.appIndexJs
is undefined, you can see how it used inconfig/webpack.config.js:403