Silly example of using the readTree promise in the previous broccoli API

example-plugin.js

function MyPlugin(inputNodes, options) {
  this.options = options;
  
  // In this example, let's say we need to do something special with the first
  // inputNode as compared to the others.
  [this.firstNode, ...this.otherNodes] = inputNodes;
}

MyPlugin.prototype.read = function(readTree) {
  let outputPaths = [];
  
  this.options.startCallback();  // first "hook" from plugin options
  
  readTree(this.firstNode).then(firstNodeOutput => {
    outputPaths.push(firstNodeOutput);
    this.options.secondCallback();  // another "hook" from plugin options
    
    return promiseMapSeries(this.otherNodes, (n) => {
      return readTree(n).then(out => {
        this.options.postEachOtherCallback();  // yet another "hook" from plugin options
        return out;
      })
    });
  }).then(([...otherNodesOutput]) => {
    outputPaths = outputPaths.concat(otherNodesOutput);
    this.options.finalCallback();  // a finished "hook" from plugin options
    return whateverWeWantToDoWith(outputPaths);
  })
}