su_nan_guan_wang/node_modules/enhanced-resolve/lib/AliasFieldPlugin.js

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

const DescriptionFileUtils = require("./DescriptionFileUtils");
const getInnerRequest = require("./getInnerRequest");

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

	apply(resolver) {
		const target = resolver.ensureHook(this.target);
		resolver
			.getHook(this.source)
			.tapAsync("AliasFieldPlugin", (request, resolveContext, callback) => {
				if (!request.descriptionFileData) return callback();
				const innerRequest = getInnerRequest(resolver, request);
				if (!innerRequest) return callback();
				const fieldData = DescriptionFileUtils.getField(
					request.descriptionFileData,
					this.field
				);
				if (typeof fieldData !== "object") {
					if (resolveContext.log)
						resolveContext.log(
							"Field '" +
								this.field +
								"' doesn't contain a valid alias configuration"
						);
					return callback();
				}
				const data1 = fieldData[innerRequest];
				const data2 = fieldData[innerRequest.replace(/^\.\//, "")];
				const data = typeof data1 !== "undefined" ? data1 : data2;
				if (data === innerRequest) return callback();
				if (data === undefined) return callback();
				if (data === false) {
					const ignoreObj = Object.assign({}, request, {
						path: false
					});
					return callback(null, ignoreObj);
				}
				const obj = Object.assign({}, request, {
					path: request.descriptionFileRoot,
					request: data
				});
				resolver.doResolve(
					target,
					obj,
					"aliased from description file " +
						request.descriptionFilePath +
						" with mapping '" +
						innerRequest +
						"' to '" +
						data +
						"'",
					resolveContext,
					(err, result) => {
						if (err) return callback(err);

						// Don't allow other aliasing or raw request
						if (result === undefined) return callback(null, null);
						callback(null, result);
					}
				);
			});
	}
};