Sync versions from yarn.lock back into package.json

yarn-sync.js

const fs = require("fs");

/**
 * Removes matching outer quotes from a string.
 *
 * @param {string} text - String to unquote
 * @returns {string} - Unquoted string
 */
const unquote = text => /(["'])?(.*)\1/.exec(text)[2];

/**
 * @typedef {object} YarnLockItem
 * @property {string[]} pkgs - Array of package version specs, e.g. "yippee-ki-yay@^1.23.45", "@foo/bar@^1.6.0"
 * @property {string} version - Installed version
 * @property {string} resolved - Resolved package URL
 * @property {string} integrity - Package integrity
 * @property {object.<string, string>} dependencies - Package dependencies and their version specs
 */

/**
 * Extracts information about installed packages from yarn.lock file.
 *
 * NB: functionality for parsing a yarn.lock file exists in a package called `@yarnpkg/lockfile`,
 * however this package pulls in way too many dependencies (all of yarn, it seems).
 *
 * @param {string} filename - Path to yarn.lock file
 * @returns {object.<string, YarnLockItem>} Installed package information, keyed by package version spec
 */
const parseYarnLockFile = s => {
  const lines = s.replace(/\r/g, "").split(/\n/);

  const entries = {};
  let entry;
  let key;

  lines.forEach(line => {
    const indent = /^(\s*)/.exec(line)[1].length;
    line = line.trim();

    if (line === "") {
      if (entry) {
        // Add an entry for each of the package specs in the item
        entry.pkgs.forEach(pkg => {
          entries[pkg] = entry;
        });
        entry = null;
      }
    } else if (line[0] === "#") {
      // Comment, skip
    } else if (indent === 0) {
      // Start of entry
      entry = {
        // Remove trailing colon, split, trim and unquote
        pkgs: line
          .replace(/:$/, "")
          .split(",")
          .map(s => unquote(s.trim()))
      };
    } else if (indent === 2) {
      let match;
      if ((match = /^(\w+) (.+)/.exec(line))) {
        entry[match[1]] = unquote(match[2]);
      } else if ((match = /^(\w+):$/.exec(line))) {
        key = match[1];
        entry[key] = {};
      }
    } else if (indent === 4) {
      const match = /^(.+) (.+)/.exec(line);
      if (match) {
        entry[key][unquote(match[1])] = unquote(match[2].trim());
      }
    } else {
      console.warn("Line not understood:", line);
    }
  });

  return entries;
};

const updatePackageJson = (packageJson, yarnLock) => {
  let changeCount = 0;

  const updateSection = sectionName => {
    console.log("Updating", sectionName, "...");

    const section = packageJson[sectionName];

    Object.entries(section).forEach(([pkg, versionSpec]) => {
      const dependency = `${pkg}@${versionSpec}`;

      // Get the version spec prefix, e.g. '^' or '>=', or none.
      // We support version specs containing a single semver, other types of version spec are untested a.t.m.
      // (version spec format is documented here: https://docs.npmjs.com/files/package.json#dependencies)
      const versionSpecPrefix = /^([^\d]*)/.exec(versionSpec)[1];

      const yarnLockEntry = yarnLock[dependency];
      if (yarnLockEntry) {
        const actualVersion = yarnLockEntry.version;
        const actualVersionSpec = `${versionSpecPrefix}${actualVersion}`;

        if (actualVersionSpec !== versionSpec) {
          console.log("  Updating:", dependency, "=>", actualVersionSpec);
          section[pkg] = actualVersionSpec;
          ++changeCount;
        } else {
          console.log("  Up-to-date:", dependency);
        }
      } else {
        console.warn("  !!! Missing yarn.lock entry for:", dependency);
      }
    });

    console.log("  Done.");
  };

  [
    "dependencies",
    "devDependencies",
    "optionalDependencies",
    "peerDependencies"
  ].forEach(sectionName => {
    if (sectionName in packageJson) {
      updateSection(sectionName);
    }
  });

  return changeCount;
};

const main = () => {
  console.log("Reading package.json ...");
  const packageJsonFile = fs.readFileSync("package.json", "utf8");
  const packageJson = JSON.parse(packageJsonFile);

  console.log("Reading yarn.lock ...");
  const yarnLockFile = fs.readFileSync("yarn.lock", "utf8");
  const yarnLock = parseYarnLockFile(yarnLockFile);

  const changeCount = updatePackageJson(packageJson, yarnLock);

  if (changeCount > 0) {
    const outFilename = "package_synced.json";
    console.log("Writing changes to:", outFilename);
    fs.writeFileSync(outFilename, JSON.stringify(packageJson, null, 2));
  } else {
    console.log("No changes");
  }
};

main();