rollup-plugin-strict-alias/src/index.js

Resolves aliases with Rollup

import path from 'path';
import fs from 'fs';

// Helper functions
const noop = () => null;
const endsWith = (needle, haystack) => haystack.slice(-needle.length) === needle;
const isFilePath = id => /^\.?\//.test(id);
const exists = uri => {
  try {
    return fs.statSync(uri).isFile();
  } catch (e) {
    return false;
  }
};

export default function alias(options = {}) {
  const hasResolve = Array.isArray(options.resolve);
  const resolve = hasResolve ? options.resolve : ['.js'];
  const aliasKeys = hasResolve ?
                      Object.keys(options).filter(k => k !== 'resolve') : Object.keys(options);

  // No aliases?
  if (!aliasKeys.length) {
    return {
      resolveId: noop,
    };
  }

  return {
    resolveId(importee, importer) {
      // First match is supposed to be the correct one
      const toReplace = aliasKeys.find(key => key === importee);

      if (!toReplace) {
        return null;
      }

      const entry = options[toReplace];

      if (isFilePath(entry)) {
        const directory = path.dirname(importer);

        // Resolve file names
        const filePath = path.resolve(directory, entry);
        const match = resolve.map(ext => `${filePath}${ext}`)
                            .find(exists);

        if (match) {
          return match;
        }

        // To keep the previous behaviour we simply return the file path
        // with extension
        if (endsWith('.js', filePath)) {
          return filePath;
        }

        return filePath + '.js';
      }

      return entry;
    },
  };
}