node_modules/enhanced-resolve/lib/SymlinkPlugin.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
"use strict";

const getPaths = require("./getPaths");
const forEachBail = require("./forEachBail");

module.exports = class SymlinkPlugin {
	constructor(source, target) {
		this.source = source;
		this.target = target;
	}

	apply(resolver) {
		const target = resolver.ensureHook(this.target);
		const fs = resolver.fileSystem;
		resolver
			.getHook(this.source)
			.tapAsync("SymlinkPlugin", (request, resolveContext, callback) => {
				const pathsResult = getPaths(request.path);
				const pathSeqments = pathsResult.seqments;
				const paths = pathsResult.paths;

				let containsSymlink = false;
				forEachBail.withIndex(
					paths,
					(path, idx, callback) => {
						fs.readlink(path, (err, result) => {
							if (!err && result) {
								pathSeqments[idx] = result;
								containsSymlink = true;
								// Shortcut when absolute symlink found
								if (/^(\/|[a-zA-Z]:($|\\))/.test(result))
									return callback(null, idx);
							}
							callback();
						});
					},
					(err, idx) => {
						if (!containsSymlink) return callback();
						const resultSeqments =
							typeof idx === "number"
								? pathSeqments.slice(0, idx + 1)
								: pathSeqments.slice();
						const result = resultSeqments.reverse().reduce((a, b) => {
							return resolver.join(a, b);
						});
						const obj = Object.assign({}, request, {
							path: result
						});
						resolver.doResolve(
							target,
							obj,
							"resolved symlink to " + result,
							resolveContext,
							callback
						);
					}
				);
			});
	}
};