index.ts

import { relative, resolve, sep } from 'path';

import { Plugin } from 'rollup';
import { createFilter } from '@rollup/pluginutils';
import { ESLint } from 'eslint';

import type { RollupEslintOptions } from '../types';

function normalizePath(id: string) {
  return relative(process.cwd(), id).split(sep).join('/');
}

export default function eslint(options = {} as RollupEslintOptions): Plugin {
  if (typeof options === 'string') {
    const configFile = resolve(process.cwd(), options);
    // eslint-disable-next-line global-require, import/no-dynamic-require, no-param-reassign
    options = require(configFile);
    // Tell eslint not to look for configuration files.
    // eslint-disable-next-line no-param-reassign
    options.useEslintrc = false;
  }

  const {
    include,
    exclude = /node_modules/,
    throwOnWarning = false,
    throwOnError = false,
    formatter = 'stylish',
    ...eslintOptions
  } = options;

  const eslintInstance = new ESLint(eslintOptions);
  const filter = createFilter(include, exclude);

  return {
    name: 'eslint',
    async transform(_, id: string) {
      const file = normalizePath(id);
      if (!filter(id) || (await eslintInstance.isPathIgnored(file))) {
        return null;
      }

      const results = await eslintInstance.lintFiles(file);
      const [result] = results;

      if (eslintOptions.fix) {
        await ESLint.outputFixes(results);
      }

      if (result.warningCount === 0 && result.errorCount === 0) {
        return null;
      }

      const eslintFormatter: ESLint.Formatter =
        typeof formatter === 'string'
          ? await eslintInstance.loadFormatter(formatter)
          : { format: formatter };
      const output = eslintFormatter.format(results);

      if (output) {
        // eslint-disable-next-line no-console
        console.log(output);
      }

      const errorMessages = [];
      if (result.warningCount > 0 && throwOnWarning) {
        errorMessages.push(`${result.warningCount} warning${result.warningCount > 1 ? 's' : ''}`);
      }

      if (result.errorCount > 0 && throwOnError) {
        errorMessages.push(`${result.errorCount} error${result.errorCount > 1 ? 's' : ''}`);
      }

      if (errorMessages.length > 0) {
        throw new Error(
          `Found ${errorMessages.join(' and ')} in ${relative('.', result.filePath)}`
        );
      }

      return null;
    }
  };
}