Typescript parsing error when EXTEND_ESLINT=true in create-react-app

UPDATE: Update react-scripts to latest version at least 3.4.1. It's fixed.

For pre 3.4.1 versions of react-scripts,

Open node_modules/react-scripts/config/webpack.config.js

Replace code block from line 365 with this code.

  if (process.env.EXTEND_ESLINT === 'true') {
    return undefined
  } else {
    return {
      extends: [require.resolve('eslint-config-react-app')],
useEslintrc: process.env.EXTEND_ESLINT === 'true',

Now if you start your app by yarn or npm, you will see it is fixed.

The fix is originally introduced here


Run npx patch-package react-scripts to make a patch for it. And add "postinstall": "patch-package" to your package.json scripts section.

The patch will be automatically applied after npm install