rollup-plugin-jscc/src/proc-file.js

Conditional comments and variable replacement for rollup, based on jscc

import fs from 'fs'
import jscc from 'jscc'

/**
 * Returns a shallow copy of the jscc options.
 *
 * @param {jscc.Options} opts
 * @returns {jscc.Options}
 */
const _getJsccOpts = opts => ({
  escapeQuotes: opts.escapeQuotes,
  keepLines: opts.keepLines,
  mapHires: opts.mapHires,
  prefixes: opts.prefixes,
  sourceMap: opts.sourceMap,
  mapContent: opts.mapContent !== false,
  values: Object.assign({}, opts.values),
})

/**
 * Simple wrapper for the async `fs.readFile` that returns a Promise that
 * resolves to a string with the content decoded as utf8.
 *
 * @param {string} fname Absolute or relative to cwd
 * @returns {Promise<string>}
 */
const _getSource = fname =>
  new Promise((resolve, reject) => {
    fs.readFile(fname, 'utf8', (error, data) => {
      // istanbul ignore if
      if (error) {
        reject(error)
      } else {
        resolve(data)
      }
    })
  })

/**
 * Call jscc and returns a Promise that is resolved with a {code,map} object
 * or a string if the buffer did not change or `options.sourceMap:false`.
 *
 * @param {string} fname Absolute or relative to cwd
 * @param {jscc.Options} options jscc options
 * @param {string} [code] Source
 * @returns {Promise<string>}
 */
const procFile = (fname, options, code) => {
  // Supports transform
  const promise = code != null ? Promise.resolve(code) : _getSource(fname)

  return promise
    .then(source => {
      // Supports buffer
      if (typeof Buffer !== 'undefined' && Buffer.isBuffer(source)) {
        source = source.toString()
      }
      // Ignore non-string sources
      return typeof source === 'string'
        ? jscc(source, fname, _getJsccOpts(options))
        : source
    })
    .then(ret => {
      /*
        change the relative source path in the source map to the input file path
        explanation:
          rollup will resolve source path through the file's directory absolute path
          and the source path in the returned source map by the plugin

            new Source(resolve(dirname(module.id), originalSourcemap.sourceRoot || '.', source), sourcesContent[i])

          @see https://github.com/rollup/rollup/blob/v1.15.6/src/utils/collapseSourcemaps.ts#L196
      */
      if (ret.map) {
        ret.map.sources[0] = fname
      }
      return ret
    })
}

export default procFile