index.js

// see: https://github.com/arackaf/customize-cra/issues/175#issuecomment-610023655
const fs = require('fs');
const eslintrcFilePath = process.cwd() + '/.eslintrc.js';
let eslintrcContent = {};

if (fs.existsSync(eslintrcFilePath)) {
  eslintrcContent = require(eslintrcFilePath);
}

const useEslintConfig = configRules => config => {
  const updatedRules = config.module.rules.map(
    rule => {
      // Only target rules that have defined a `useEslintrc` parameter in their options
      if (rule.use && rule.use.some( use => use.options && use.options.useEslintrc !== void 0)) {
        const ruleUse = rule.use[0];
        const baseOptions = ruleUse.options;
        const baseConfig = baseOptions.baseConfig || {};
        const newOptions = {
          useEslintrc: false,
          ignore: true,
          baseConfig: { ...baseConfig, ...(configRules || eslintrcContent)}
        }
        ruleUse.options = newOptions;
        return rule;

      // Rule not using eslint. Do not modify.
      } else {
        return rule;
      }
    }
  );

  config.module.rules = updatedRules;
  return config;
};

module.exports = useEslintConfig;