yarn-sync.js

/** @format */

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();