Broccoli Babel Plugin with and without Promises

1_brocbab_pre-promise.js

// Unfinished - before throwing up hands and moving on to refactor

Babel.prototype.write = function(readTree, destDir) {
  var self = this;

  return readTree(self.inputTree).then(function(srcDir) { 
    var promise = new rsvp.Promise(function(resolve, reject) {

      recreaddir(srcDir, function(err, files) {

        files = files.forEach(function(file, index) {
          // Normalize recursive-readdir path output
          file = file.replace(/\\/g, '/');
          file = file.replace(srcDir+'/', '');

          var relativePath = srcDir + '/' + file;
          var destinatPath = destDir + '/' + file;

          if(path.extname(file) !== '.'+self.targetExtension) {
            fs.readFile(relativePath, 'utf8', function(data) {
              fs.writeFile(destinatPath, data);
            });

            if(index === files.length-1) {
              resolve(srcDir);
            }
            return;
          }

          var options = self.copyOptions();

          options.filename = options.sourceMapName = options.sourceFileName = relativePath;

          fs.readFile(relativePath, 'utf8', function(string) {
            var result = self.transform(string, options);

            var subpath = path.dirname(destinatPath);

            fs.stat(subpath, function(err, stats) {
              if(!stats.isDirectory()) {
                mkpath(subpath, function() {
                  fs.writeFile(destinatPath, result.code, function() {
                    if(index === files.length-1 && !result.map) {
                      resolve(srcDir);
                    }
                  });
                  if(result.map) {
                    fs.writeFile(destinatPath + '.map', JSON.stringify(result.map));
                  }
                })
              } else {
                fs.writeFile(destinatPath, result.code);
                if(result.map) {
                  fs.writeFile(destinatPath + '.map', JSON.stringify(result.map));
                }
              }
            });

          });

        });

      });

    });

    return promise;
  });
};

2_brocbab_promise.js

Babel.prototype.write = function(readTree, destDir) {
  var self = this;

  return readTree(self.inputTree).then(function(srcDir) {

    return deepList(srcDir).then(function(files) {
      // File list is converted into promise collection as output is written.
      return rsvp.all(files.map(function(file) {
        var src = file,
            dest = file.replace(srcDir, destDir);

        var options = self.copyOptions();
        options.filename = options.sourceMapName = options.sourceFileName = src;

        return readAndTranspile(src, options, self.extensions).then(function(data) {
          return writeOutput(dest, data, self.targetExtension);
        });
      }));
    });
  });
};

3_brocbab_async-await.js

// Just-for-fun addition a few years later

Babel.prototype.write = async function(readTree, destDir) {
  const srcDir = await readTree(this.inputTree);
  const files = await deepList(srcDir)
  
  const output = await Promise.all(files.map(async file => {
    const src = file,
          dest = file.replace(srcDir, destDir);

    const options = this.copyOptions();
    options.filename = options.sourceMapName = options.sourceFileName = src;

    const data = await readAndTranspile(src, options, this.extensions);
    return writeOutput(dest, data, this.targetExtension);
  }));
  
  return output;
};