gatsby-plugin-perf-budgets/lib/analyzer.js

**gatsby-plugin-perf-budgets** is an *experimental* plugin to make browsing bundles on a page basis easier. It is used in conjunction with `gatsby-plugin-webpack-bundle-analyser-v2`.

"use strict";

const fs = require("fs");

const path = require("path");

const _ = require("lodash");

const gzipSize = require("gzip-size");

const Logger = require("./Logger");

const Folder = require("./tree/Folder").default;

const {
  parseBundle
} = require("./parseUtils");

const {
  createAssetsFilter
} = require("./utils");

const FILENAME_QUERY_REGEXP = /\?.*$/u;
const FILENAME_EXTENSIONS = /\.(js|mjs)$/iu;
module.exports = {
  getViewerData,
  readStatsFromFile
};

function getViewerData(bundleStats, bundleDir, opts) {
  const {
    logger = new Logger(),
    excludeAssets = null
  } = opts || {};
  const isAssetIncluded = createAssetsFilter(excludeAssets); // Sometimes all the information is located in `children` array (e.g. problem in #10)

  if (_.isEmpty(bundleStats.assets) && !_.isEmpty(bundleStats.children)) {
    bundleStats = bundleStats.children[0];
  } // Picking only `*.js or *.mjs` assets from bundle that has non-empty `chunks` array


  bundleStats.assets = _.filter(bundleStats.assets, asset => {
    // Removing query part from filename (yes, somebody uses it for some reason and Webpack supports it)
    // See #22
    asset.name = asset.name.replace(FILENAME_QUERY_REGEXP, "");
    return FILENAME_EXTENSIONS.test(asset.name) && !_.isEmpty(asset.chunks) && isAssetIncluded(asset.name);
  }); // Trying to parse bundle assets and get real module sizes if `bundleDir` is provided

  let bundlesSources = null;
  let parsedModules = null;

  if (bundleDir) {
    bundlesSources = {};
    parsedModules = {};

    for (const statAsset of bundleStats.assets) {
      const assetFile = path.join(bundleDir, statAsset.name);
      let bundleInfo;

      try {
        bundleInfo = parseBundle(assetFile);
      } catch (err) {
        const msg = err.code === "ENOENT" ? "no such file" : err.message;
        logger.warn(`Error parsing bundle asset "${assetFile}": ${msg}`);
        continue;
      }

      bundlesSources[statAsset.name] = bundleInfo.src;

      _.assign(parsedModules, bundleInfo.modules);
    }

    if (_.isEmpty(bundlesSources)) {
      bundlesSources = null;
      parsedModules = null;
      logger.warn("\nNo bundles were parsed. Analyzer will show only original module sizes from stats file.\n");
    }
  }

  const modules = getBundleModules(bundleStats);

  const assets = _.transform(bundleStats.assets, (result, statAsset) => {
    const asset = result[statAsset.name] = _.pick(statAsset, "size");

    asset.chunkName = statAsset.chunkNames && statAsset.chunkNames[0] || null;

    if (bundlesSources && _.has(bundlesSources, statAsset.name)) {
      asset.parsedSize = Buffer.byteLength(bundlesSources[statAsset.name]);
      asset.gzipSize = gzipSize.sync(bundlesSources[statAsset.name]);
    } // Picking modules from current bundle script


    asset.modules = _(modules).filter(statModule => assetHasModule(statAsset, statModule)).each(statModule => {
      if (parsedModules) {
        statModule.parsedSrc = parsedModules[statModule.id];
      }
    });
    asset.tree = createModulesTree(asset.modules);
  }, {});

  return _.transform(assets, (result, asset, filename) => {
    result.push({
      label: filename,
      isAsset: true,
      // Not using `asset.size` here provided by Webpack because it can be very confusing when `UglifyJsPlugin` is used.
      // In this case all module sizes from stats file will represent unminified module sizes, but `asset.size` will
      // be the size of minified bundle.
      // Using `asset.size` only if current asset doesn't contain any modules (resulting size equals 0)
      statSize: asset.tree.size || asset.size,
      parsedSize: asset.parsedSize,
      gzipSize: asset.gzipSize,
      groups: _.invokeMap(asset.tree.children, "toChartData"),
      chunkName: asset.chunkName
    });
  }, []);
}

function readStatsFromFile(filename) {
  return JSON.parse(fs.readFileSync(filename, "utf8"));
}

function getBundleModules(bundleStats) {
  return _(bundleStats.chunks).map("modules").concat(bundleStats.modules).compact().flatten().uniqBy("id").value();
}

function assetHasModule(statAsset, statModule) {
  // Checking if this module is the part of asset chunks
  return _.some(statModule.chunks, moduleChunk => _.includes(statAsset.chunks, moduleChunk));
}

function createModulesTree(modules) {
  const root = new Folder(".");

  _.each(modules, module => root.addModule(module));

  root.mergeNestedFolders();
  return root;
}