index.js

var fs = require("fs");
var fse = require("fs-extra");

var DEFAULT_PARAMS = {
  manifestFile: "../../config/sprockets-manifest.json",
  statsFile: "webpack-stats.json"
};

function WebpackSprocketsRailsManifestPlugin(options) {
  var params = options || {};

  this._manifestFile = params.manifestFile || DEFAULT_PARAMS.manifestFile;
  this._statsFile = params.statsFile || DEFAULT_PARAMS.statsFile;
}

WebpackSprocketsRailsManifestPlugin.prototype.apply = function(compiler) {
  var manifestFile = this._manifestFile;
  var statsFile = this._statsFile;
  var sprockets = {
    files: {},
    assets: {}
  };

  compiler.plugin("done", function(stats) {
    var statsJson = stats.toJson();
    var chunks = statsJson.chunks;
    var devServer = compiler.options.devServer;
    var outputPath;

    if (devServer && devServer.contentBase) {
      outputPath = devServer.contentBase;
    } else {
      outputPath = compiler.options.output.path;
    }

    var manifestPath = outputPath + "/" + manifestFile;

    chunks.forEach(function(chunk) {
      chunk.files.forEach(function (chunkFilename) {
        var chunkPath = outputPath + "/" + chunkFilename;
        var chunkExtension = chunkFilename.split(".").pop();
        var logicalPath = chunk.names[0] + "." + chunkExtension;
        var mtime;

        if (fs.existsSync(chunkPath)) {
          mtime = fs.statSync(chunkPath).mtime;
        } else {
          mtime = new Date();
        }

        sprockets.files[chunkFilename] = {
          "logical_path": logicalPath,
          "mtime": mtime.toISOString(),
          "size": chunk.size,
          "digest": chunk.hash,
          // TODO
          // "integrity": "sha256-Zk2O+Q1SFSuzslxNc6LuqFrAN5PlRHlbKeGzXfN4Xmc="
        };
        sprockets.assets[logicalPath] = chunkFilename;
      });
    });

    fse.mkdirpSync(outputPath);
    fse.outputFileSync(manifestPath, JSON.stringify(sprockets, null, "  "));
  });
};

module.exports = WebpackSprocketsRailsManifestPlugin;