rollup-plugin-visualizer/plugin/sourcemap.js

[](https://npmjs.org/package/rollup-plugin-visualizer) [](https://travis-ci.com/btd/rollu

"use strict";

const path = require("path");

const { SourceMapConsumer } = require("source-map");

const getBytesPerFileUsingSourceMap = (code, map) => {
  const lines = code.split(/[\r\n]/);

  const bytesPerFile = {};

  // For every byte in the minified code, do a sourcemap lookup.
  for (let line = 0; line < lines.length; line++) {
    for (let col = 0; col < lines[line].length; col++) {
      const result = map.originalPositionFor({ line: line + 1, column: col });
      const source = result.source || "root";
      if (!bytesPerFile[source]) {
        bytesPerFile[source] = 0;
      }
      bytesPerFile[source]++;
    }
  }
  return Object.keys(bytesPerFile).map(file => ({
    file: path.resolve(file),
    bytes: bytesPerFile[file]
  }));
};

// Given a file C:/path/to/file/on/filesystem.js
// - remove extension
// - strip filesystem root
// - return path segments, starting from the tail and working backwards
// segments('C:/path/to/file/on/filesystem.js') === ['filesystem', 'on', 'file', 'to', 'path']
const segments = filepath => {
  const parsed = path.parse(filepath);
  const dirWithoutRoot = parsed.dir.substring(parsed.root.length);

  return dirWithoutRoot
    .split(path.sep)
    .concat(parsed.name)
    .reverse();
};

// Adds a .minifiedSize property to each module in the bundle (using sourcemap data)
// If the minified size could not be computed, no property is added.
// Module id are mapped to sources by finding the best match.
// Matching is done by removing the file extensions and comparing path segments
const addMinifiedSizesToModules = bundle => {
  const findBestMatchingModule = filename => {
    const filenameSegments = segments(filename);

    for (let i = 1; i <= filenameSegments.length; i++) {
      const leftVals = filenameSegments.slice(0, i);

      const matches = Object.keys(bundle.modules).filter(id => {
        const moduleSegments = segments(id);
        const rightVals = moduleSegments.slice(0, i);
        if (rightVals.length !== leftVals.length) {
          return false;
        }
        return rightVals.every((rightVal, i) => rightVal === leftVals[i]);
      });

      if (matches.length === 1) {
        return bundle.modules[matches[0]];
      }
    }

    return null;
  };

  return SourceMapConsumer.with(bundle.map, null, map => {
    const fileSizes = getBytesPerFileUsingSourceMap(bundle.code, map);
    fileSizes.forEach(tuple => {
      const module = findBestMatchingModule(tuple.file);
      if (module) {
        module.minifiedSize = tuple.bytes;
      }
    });
  });
};

module.exports = addMinifiedSizesToModules;