webpack/lib/ExternalModule.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

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

"use strict";

const { SyncBailHook } = require("tapable");
const { OriginalSource, RawSource } = require("webpack-sources");
const ConcatenationScope = require("./ConcatenationScope");
const EnvironmentNotSupportAsyncWarning = require("./EnvironmentNotSupportAsyncWarning");
const { UsageState } = require("./ExportsInfo");
const InitFragment = require("./InitFragment");
const Module = require("./Module");
const {
	CSS_IMPORT_TYPES,
	CSS_URL_TYPES,
	JAVASCRIPT_TYPE,
	JAVASCRIPT_TYPES
} = require("./ModuleSourceTypeConstants");
const { JAVASCRIPT_MODULE_TYPE_DYNAMIC } = require("./ModuleTypeConstants");
const RuntimeGlobals = require("./RuntimeGlobals");
const Template = require("./Template");
const { DEFAULTS } = require("./config/defaults");
const StaticExportsDependency = require("./dependencies/StaticExportsDependency");
const createHash = require("./util/createHash");
const extractUrlAndGlobal = require("./util/extractUrlAndGlobal");
const makeSerializable = require("./util/makeSerializable");
const { propertyAccess } = require("./util/property");
const { register } = require("./util/serialization");

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../declarations/WebpackOptions").ExternalsType} ExternalsType */
/** @typedef {import("../declarations/WebpackOptions").HashFunction} HashFunction */
/** @typedef {import("./config/defaults").WebpackOptionsNormalizedWithDefaults} WebpackOptions */
/** @typedef {import("./Chunk")} Chunk */
/** @typedef {import("./ChunkGraph")} ChunkGraph */
/** @typedef {import("./Compilation")} Compilation */
/** @typedef {import("./Compilation").UnsafeCacheData} UnsafeCacheData */
/** @typedef {import("./Dependency").UpdateHashContext} UpdateHashContext */
/** @typedef {import("./ExportsInfo")} ExportsInfo */
/** @typedef {import("./Generator").GenerateContext} GenerateContext */
/** @typedef {import("./Generator").SourceTypes} SourceTypes */
/** @typedef {import("./Module").ModuleId} ModuleId */
/** @typedef {import("./Module").BuildCallback} BuildCallback */
/** @typedef {import("./Module").BuildInfo} BuildInfo */
/** @typedef {import("./Module").CodeGenerationContext} CodeGenerationContext */
/** @typedef {import("./Module").CodeGenerationResult} CodeGenerationResult */
/** @typedef {import("./Module").CodeGenerationResultData} CodeGenerationResultData */
/** @typedef {import("./Module").ConcatenationBailoutReasonContext} ConcatenationBailoutReasonContext */
/** @typedef {import("./Module").LibIdentOptions} LibIdentOptions */
/** @typedef {import("./Module").LibIdent} LibIdent */
/** @typedef {import("./Module").NeedBuildCallback} NeedBuildCallback */
/** @typedef {import("./Module").NeedBuildContext} NeedBuildContext */
/** @typedef {import("./Module").RuntimeRequirements} RuntimeRequirements */
/** @typedef {import("./Module").ReadOnlyRuntimeRequirements} ReadOnlyRuntimeRequirements */
/** @typedef {import("./Module").Sources} Sources */
/** @typedef {import("./ModuleGraph")} ModuleGraph */
/** @typedef {import("./NormalModuleFactory")} NormalModuleFactory */
/** @typedef {import("./RequestShortener")} RequestShortener */
/** @typedef {import("./ResolverFactory").ResolverWithOptions} ResolverWithOptions */
/** @typedef {import("./RuntimeTemplate")} RuntimeTemplate */
/** @typedef {import("./javascript/JavascriptModulesPlugin").ChunkRenderContext} ChunkRenderContext */
/** @typedef {import("./javascript/JavascriptParser").ImportAttributes} ImportAttributes */
/** @typedef {import("./serialization/ObjectMiddleware").ObjectDeserializerContext} ObjectDeserializerContext */
/** @typedef {import("./serialization/ObjectMiddleware").ObjectSerializerContext} ObjectSerializerContext */
/** @typedef {import("./util/Hash")} Hash */
/** @typedef {import("./util/fs").InputFileSystem} InputFileSystem */
/** @typedef {import("./util/runtime").RuntimeSpec} RuntimeSpec */

/** @typedef {{ attributes?: ImportAttributes, externalType: "import" | "module" | undefined }} ImportDependencyMeta */
/** @typedef {{ layer?: string, supports?: string, media?: string }} CssImportDependencyMeta */
/** @typedef {{ sourceType: "css-url" }} AssetDependencyMeta */

/** @typedef {ImportDependencyMeta | CssImportDependencyMeta | AssetDependencyMeta} DependencyMeta */

/**
 * Defines the source data type used by this module.
 * @typedef {object} SourceData
 * @property {boolean=} iife
 * @property {string=} init
 * @property {string} expression
 * @property {InitFragment<ChunkRenderContext>[]=} chunkInitFragments
 * @property {ReadOnlyRuntimeRequirements=} runtimeRequirements
 * @property {[string, string][]=} specifiers
 */

/** @typedef {true | [string, string][]} Imported */

/** @type {RuntimeRequirements} */
const RUNTIME_REQUIREMENTS = new Set([RuntimeGlobals.module]);
/** @type {RuntimeRequirements} */
const RUNTIME_REQUIREMENTS_FOR_SCRIPT = new Set([RuntimeGlobals.loadScript]);
/** @type {RuntimeRequirements} */
const RUNTIME_REQUIREMENTS_FOR_MODULE = new Set([
	RuntimeGlobals.definePropertyGetters
]);
/** @type {RuntimeRequirements} */
const EMPTY_RUNTIME_REQUIREMENTS = new Set();

/**
 * Gets source for global variable external.
 * @param {string | string[]} variableName the variable name or path
 * @param {string} type the module system
 * @returns {SourceData} the generated source
 */
const getSourceForGlobalVariableExternal = (variableName, type) => {
	if (!Array.isArray(variableName)) {
		// make it an array as the look up works the same basically
		variableName = [variableName];
	}

	// needed for e.g. window["some"]["thing"]
	const objectLookup = variableName
		.map((r) => `[${JSON.stringify(r)}]`)
		.join("");
	return {
		iife: type === "this",
		expression: `${type}${objectLookup}`
	};
};

/** @typedef {string | string[]} ModuleAndSpecifiers */

/**
 * Gets source for common js external.
 * @param {ModuleAndSpecifiers} moduleAndSpecifiers the module request
 * @returns {SourceData} the generated source
 */
const getSourceForCommonJsExternal = (moduleAndSpecifiers) => {
	if (!Array.isArray(moduleAndSpecifiers)) {
		return {
			expression: `require(${JSON.stringify(moduleAndSpecifiers)})`
		};
	}
	const moduleName = moduleAndSpecifiers[0];
	return {
		expression: `require(${JSON.stringify(moduleName)})${propertyAccess(
			moduleAndSpecifiers,
			1
		)}`
	};
};

/**
 * Gets external module node commonjs init fragment.
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {InitFragment<ChunkRenderContext>} code
 */
const getExternalModuleNodeCommonjsInitFragment = (runtimeTemplate) => {
	const importMetaName = runtimeTemplate.outputOptions.importMetaName;

	return new InitFragment(
		`import { createRequire as __WEBPACK_EXTERNAL_createRequire } from ${runtimeTemplate.renderNodePrefixForCoreModule(
			"module"
		)};\n${runtimeTemplate.renderConst()} __WEBPACK_EXTERNAL_createRequire_require = __WEBPACK_EXTERNAL_createRequire(${importMetaName}.url);\n`,
		InitFragment.STAGE_HARMONY_IMPORTS,
		0,
		"external module node-commonjs"
	);
};

/**
 * Gets source for common js external in node module.
 * @param {ModuleAndSpecifiers} moduleAndSpecifiers the module request
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {SourceData} the generated source
 */
const getSourceForCommonJsExternalInNodeModule = (
	moduleAndSpecifiers,
	runtimeTemplate
) => {
	const chunkInitFragments = [
		getExternalModuleNodeCommonjsInitFragment(runtimeTemplate)
	];
	if (!Array.isArray(moduleAndSpecifiers)) {
		return {
			chunkInitFragments,
			expression: `__WEBPACK_EXTERNAL_createRequire_require(${JSON.stringify(
				moduleAndSpecifiers
			)})`
		};
	}
	const moduleName = moduleAndSpecifiers[0];
	return {
		chunkInitFragments,
		expression: `__WEBPACK_EXTERNAL_createRequire_require(${JSON.stringify(
			moduleName
		)})${propertyAccess(moduleAndSpecifiers, 1)}`
	};
};

/**
 * Gets source for import external.
 * @param {ModuleAndSpecifiers} moduleAndSpecifiers the module request
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @param {ImportDependencyMeta=} dependencyMeta the dependency meta
 * @returns {SourceData} the generated source
 */
const getSourceForImportExternal = (
	moduleAndSpecifiers,
	runtimeTemplate,
	dependencyMeta
) => {
	const importName = runtimeTemplate.outputOptions.importFunctionName;
	if (
		!runtimeTemplate.supportsDynamicImport() &&
		(importName === "import" || importName === "module-import")
	) {
		throw new Error(
			"The target environment doesn't support 'import()' so it's not possible to use external type 'import'"
		);
	}
	const attributes =
		dependencyMeta && dependencyMeta.attributes
			? dependencyMeta.attributes._isLegacyAssert
				? `, { assert: ${JSON.stringify(
						dependencyMeta.attributes,
						importAssertionReplacer
					)} }`
				: `, { with: ${JSON.stringify(dependencyMeta.attributes)} }`
			: "";
	if (!Array.isArray(moduleAndSpecifiers)) {
		return {
			expression: `${importName}(${JSON.stringify(
				moduleAndSpecifiers
			)}${attributes});`
		};
	}
	if (moduleAndSpecifiers.length === 1) {
		return {
			expression: `${importName}(${JSON.stringify(
				moduleAndSpecifiers[0]
			)}${attributes});`
		};
	}
	const moduleName = moduleAndSpecifiers[0];
	return {
		expression: `${importName}(${JSON.stringify(
			moduleName
		)}${attributes}).then(${runtimeTemplate.returningFunction(
			`module${propertyAccess(moduleAndSpecifiers, 1)}`,
			"module"
		)});`
	};
};

/**
 * Import assertion replacer.
 * @param {string} key key
 * @param {ImportAttributes | string | boolean | undefined} value value
 * @returns {ImportAttributes | string | boolean | undefined} replaced value
 */
const importAssertionReplacer = (key, value) => {
	if (key === "_isLegacyAssert") {
		return;
	}

	return value;
};

/**
 * Represents ModuleExternalInitFragment.
 * @extends {InitFragment<GenerateContext>}
 */
class ModuleExternalInitFragment extends InitFragment {
	/**
	 * Creates an instance of ModuleExternalInitFragment.
	 * @param {string} request import source
	 * @param {Imported} imported the imported specifiers
	 * @param {string=} ident recomputed ident
	 * @param {ImportDependencyMeta=} dependencyMeta the dependency meta
	 * @param {HashFunction=} hashFunction the hash function to use
	 */
	constructor(
		request,
		imported,
		ident,
		dependencyMeta,
		hashFunction = DEFAULTS.HASH_FUNCTION
	) {
		if (ident === undefined) {
			ident = Template.toIdentifier(request);
			if (ident !== request) {
				ident += `_${createHash(hashFunction)
					.update(request)
					.digest("hex")
					.slice(0, 8)}`;
			}
		}

		super(
			"",
			InitFragment.STAGE_HARMONY_IMPORTS,
			0,
			`external module import ${ident} ${imported === true ? imported : imported.join(" ")}`
		);
		this._ident = ident;
		this._request = request;
		this._dependencyMeta = dependencyMeta;
		this._identifier = this.buildIdentifier(ident);
		this._imported = this.buildImported(imported);
	}

	/**
	 * Returns imported.
	 * @returns {Imported} imported
	 */
	getImported() {
		return this._imported;
	}

	/**
	 * Updates imported using the provided imported.
	 * @param {Imported} imported imported
	 */
	setImported(imported) {
		this._imported = imported;
	}

	/**
	 * Returns the source code that will be included as initialization code.
	 * @param {GenerateContext} context context
	 * @returns {string | Source | undefined} the source code that will be included as initialization code
	 */
	getContent(context) {
		const {
			_dependencyMeta: dependencyMeta,
			_imported: imported,
			_request: request,
			_identifier: identifier
		} = this;
		const attributes =
			dependencyMeta && dependencyMeta.attributes
				? dependencyMeta.attributes._isLegacyAssert &&
					dependencyMeta.attributes._isLegacyAssert
					? ` assert ${JSON.stringify(
							dependencyMeta.attributes,
							importAssertionReplacer
						)}`
					: ` with ${JSON.stringify(dependencyMeta.attributes)}`
				: "";
		let content = "";
		if (imported === true) {
			// namespace
			content = `import * as ${identifier} from ${JSON.stringify(request)}${
				attributes
			};\n`;
		} else if (imported.length === 0) {
			// just import, no use
			content = `import ${JSON.stringify(request)}${attributes};\n`;
		} else {
			content = `import { ${imported
				.map(([name, finalName]) => {
					if (name !== finalName) {
						return `${name} as ${finalName}`;
					}
					return name;
				})
				.join(", ")} } from ${JSON.stringify(request)}${attributes};\n`;
		}
		return content;
	}

	getNamespaceIdentifier() {
		return this._identifier;
	}

	/**
	 * Returns identifier.
	 * @param {string} ident ident
	 * @returns {string} identifier
	 */
	buildIdentifier(ident) {
		return `__WEBPACK_EXTERNAL_MODULE_${ident}__`;
	}

	/**
	 * Returns normalized imported.
	 * @param {Imported} imported imported
	 * @returns {Imported} normalized imported
	 */
	buildImported(imported) {
		if (Array.isArray(imported)) {
			return imported.map(([name]) => {
				const ident = `${this._ident}_${name}`;
				return [name, this.buildIdentifier(ident)];
			});
		}
		return imported;
	}
}

register(
	ModuleExternalInitFragment,
	"webpack/lib/ExternalModule",
	"ModuleExternalInitFragment",
	{
		serialize(obj, { write }) {
			write(obj._request);
			write(obj._imported);
			write(obj._ident);
			write(obj._dependencyMeta);
		},
		deserialize({ read }) {
			return new ModuleExternalInitFragment(read(), read(), read(), read());
		}
	}
);

/**
 * Generates module remapping.
 * @param {string} input input
 * @param {ExportsInfo} exportsInfo the exports info
 * @param {RuntimeSpec=} runtime the runtime
 * @param {RuntimeTemplate=} runtimeTemplate the runtime template
 * @returns {string | undefined} the module remapping
 */
const generateModuleRemapping = (
	input,
	exportsInfo,
	runtime,
	runtimeTemplate
) => {
	if (exportsInfo.otherExportsInfo.getUsed(runtime) === UsageState.Unused) {
		/** @type {string[]} */
		const properties = [];
		for (const exportInfo of exportsInfo.orderedExports) {
			const used = exportInfo.getUsedName(exportInfo.name, runtime);
			if (!used) continue;
			const nestedInfo = exportInfo.getNestedExportsInfo();
			if (nestedInfo) {
				const nestedExpr = generateModuleRemapping(
					`${input}${propertyAccess([exportInfo.name])}`,
					nestedInfo
				);
				if (nestedExpr) {
					properties.push(`[${JSON.stringify(used)}]: y(${nestedExpr})`);
					continue;
				}
			}
			properties.push(
				`[${JSON.stringify(used)}]: ${
					/** @type {RuntimeTemplate} */ (runtimeTemplate).returningFunction(
						`${input}${propertyAccess([exportInfo.name])}`
					)
				}`
			);
		}
		return `x({ ${properties.join(", ")} })`;
	}
};

/**
 * Gets source for module external.
 * @param {ModuleAndSpecifiers} moduleAndSpecifiers the module request
 * @param {ExportsInfo} exportsInfo exports info of this module
 * @param {RuntimeSpec} runtime the runtime
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @param {ImportDependencyMeta} dependencyMeta the dependency meta
 * @param {ConcatenationScope=} concatenationScope concatenationScope
 * @returns {SourceData} the generated source
 */
const getSourceForModuleExternal = (
	moduleAndSpecifiers,
	exportsInfo,
	runtime,
	runtimeTemplate,
	dependencyMeta,
	concatenationScope
) => {
	/** @type {Imported} */
	let imported = true;
	if (concatenationScope) {
		const usedExports = exportsInfo.getUsedExports(runtime);
		switch (usedExports) {
			case true:
			case null:
				// unknown exports
				imported = true;
				break;
			case false:
				// no used exports
				imported = [];
				break;
			default:
				imported = [...usedExports.entries()];
		}
	}

	if (!Array.isArray(moduleAndSpecifiers)) {
		moduleAndSpecifiers = [moduleAndSpecifiers];
	}

	// Return to `namespace` when the external request includes a specific export
	if (moduleAndSpecifiers.length > 1) {
		imported = true;
	}

	const initFragment = new ModuleExternalInitFragment(
		moduleAndSpecifiers[0],
		imported,
		undefined,
		dependencyMeta,
		runtimeTemplate.outputOptions.hashFunction
	);
	const normalizedImported = initFragment.getImported();

	const baseAccess = `${initFragment.getNamespaceIdentifier()}${propertyAccess(
		moduleAndSpecifiers,
		1
	)}`;
	let expression = baseAccess;

	const useNamespace = imported === true;
	/** @type {undefined | string} */
	let moduleRemapping;
	if (useNamespace) {
		moduleRemapping = generateModuleRemapping(
			baseAccess,
			exportsInfo,
			runtime,
			runtimeTemplate
		);
		expression = moduleRemapping || baseAccess;
	}
	return {
		expression,
		init: moduleRemapping
			? `var x = ${runtimeTemplate.basicFunction(
					"y",
					`var x = {}; ${RuntimeGlobals.definePropertyGetters}(x, y); return x`
				)} \nvar y = ${runtimeTemplate.returningFunction(
					runtimeTemplate.returningFunction("x"),
					"x"
				)}`
			: undefined,
		specifiers: normalizedImported === true ? undefined : normalizedImported,
		runtimeRequirements: moduleRemapping
			? RUNTIME_REQUIREMENTS_FOR_MODULE
			: undefined,
		chunkInitFragments: [
			/** @type {InitFragment<EXPECTED_ANY>} */ (initFragment)
		]
	};
};

/**
 * Gets source for script external.
 * @param {string | string[]} urlAndGlobal the script request
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {SourceData} the generated source
 */
const getSourceForScriptExternal = (urlAndGlobal, runtimeTemplate) => {
	if (typeof urlAndGlobal === "string") {
		urlAndGlobal = extractUrlAndGlobal(urlAndGlobal);
	}
	const url = urlAndGlobal[0];
	const globalName = urlAndGlobal[1];
	return {
		init: "var __webpack_error__ = new Error();",
		expression: `new Promise(${runtimeTemplate.basicFunction(
			"resolve, reject",
			[
				`if(typeof ${globalName} !== "undefined") return resolve();`,
				`${RuntimeGlobals.loadScript}(${JSON.stringify(
					url
				)}, ${runtimeTemplate.basicFunction("event", [
					`if(typeof ${globalName} !== "undefined") return resolve();`,
					"var errorType = event && (event.type === 'load' ? 'missing' : event.type);",
					"var realSrc = event && event.target && event.target.src;",
					"__webpack_error__.message = 'Loading script failed.\\n(' + errorType + ': ' + realSrc + ')';",
					"__webpack_error__.name = 'ScriptExternalLoadError';",
					"__webpack_error__.type = errorType;",
					"__webpack_error__.request = realSrc;",
					"reject(__webpack_error__);"
				])}, ${JSON.stringify(globalName)});`
			]
		)}).then(${runtimeTemplate.returningFunction(
			`${globalName}${propertyAccess(urlAndGlobal, 2)}`
		)})`,
		runtimeRequirements: RUNTIME_REQUIREMENTS_FOR_SCRIPT
	};
};

/**
 * Checks external variable.
 * @param {string} variableName the variable name to check
 * @param {string} request the request path
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {string} the generated source
 */
const checkExternalVariable = (variableName, request, runtimeTemplate) =>
	`if(typeof ${variableName} === 'undefined') { ${runtimeTemplate.throwMissingModuleErrorBlock(
		{ request }
	)} }\n`;

/**
 * Gets source for amd or umd external.
 * @param {ModuleId | string} id the module id
 * @param {boolean} optional true, if the module is optional
 * @param {string | string[]} request the request path
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {SourceData} the generated source
 */
const getSourceForAmdOrUmdExternal = (
	id,
	optional,
	request,
	runtimeTemplate
) => {
	const externalVariable = `__WEBPACK_EXTERNAL_MODULE_${Template.toIdentifier(
		`${id}`
	)}__`;
	return {
		init: optional
			? checkExternalVariable(
					externalVariable,
					Array.isArray(request) ? request.join(".") : request,
					runtimeTemplate
				)
			: undefined,
		expression: externalVariable
	};
};

/**
 * Gets source for default case.
 * @param {boolean} optional true, if the module is optional
 * @param {string | string[]} request the request path
 * @param {RuntimeTemplate} runtimeTemplate the runtime template
 * @returns {SourceData} the generated source
 */
const getSourceForDefaultCase = (optional, request, runtimeTemplate) => {
	if (!Array.isArray(request)) {
		// make it an array as the look up works the same basically
		request = [request];
	}

	const variableName = request[0];
	const objectLookup = propertyAccess(request, 1);
	return {
		init: optional
			? checkExternalVariable(variableName, request.join("."), runtimeTemplate)
			: undefined,
		expression: `${variableName}${objectLookup}`
	};
};

/** @typedef {Record<string, string | string[]>} RequestRecord */
/** @typedef {string | string[] | RequestRecord} ExternalModuleRequest */

/**
 * Defines the external module hooks type used by this module.
 * @typedef {object} ExternalModuleHooks
 * @property {SyncBailHook<[Chunk, Compilation], boolean>} chunkCondition
 */

/** @type {WeakMap<Compilation, ExternalModuleHooks>} */
const compilationHooksMap = new WeakMap();

class ExternalModule extends Module {
	/**
	 * Creates an instance of ExternalModule.
	 * @param {ExternalModuleRequest} request request
	 * @param {ExternalsType} type type
	 * @param {string} userRequest user request
	 * @param {DependencyMeta=} dependencyMeta dependency meta
	 */
	constructor(request, type, userRequest, dependencyMeta) {
		super(JAVASCRIPT_MODULE_TYPE_DYNAMIC, null);

		// Info from Factory
		/** @type {ExternalModuleRequest} */
		this.request = request;
		/** @type {ExternalsType} */
		this.externalType = type;
		/** @type {string} */
		this.userRequest = userRequest;
		/** @type {DependencyMeta=} */
		this.dependencyMeta = dependencyMeta;
	}

	/**
	 * Returns the attached hooks.
	 * @param {Compilation} compilation the compilation
	 * @returns {ExternalModuleHooks} the attached hooks
	 */
	static getCompilationHooks(compilation) {
		let hooks = compilationHooksMap.get(compilation);
		if (hooks === undefined) {
			hooks = {
				chunkCondition: new SyncBailHook(["chunk", "compilation"])
			};
			compilationHooksMap.set(compilation, hooks);
		}
		return hooks;
	}

	/**
	 * Returns the source types this module can generate.
	 * @returns {SourceTypes} types available (do not mutate)
	 */
	getSourceTypes() {
		if (
			this.externalType === "asset" &&
			this.dependencyMeta &&
			/** @type {AssetDependencyMeta} */
			(this.dependencyMeta).sourceType === "css-url"
		) {
			return CSS_URL_TYPES;
		} else if (this.externalType === "css-import") {
			return CSS_IMPORT_TYPES;
		}

		return JAVASCRIPT_TYPES;
	}

	/**
	 * Gets the library identifier.
	 * @param {LibIdentOptions} options options
	 * @returns {LibIdent | null} an identifier for library inclusion
	 */
	libIdent(options) {
		return this.userRequest;
	}

	/**
	 * Returns true if the module can be placed in the chunk.
	 * @param {Chunk} chunk the chunk which condition should be checked
	 * @param {Compilation} compilation the compilation
	 * @returns {boolean} true if the module can be placed in the chunk
	 */
	chunkCondition(chunk, compilation) {
		const { chunkCondition } = ExternalModule.getCompilationHooks(compilation);
		const condition = chunkCondition.call(chunk, compilation);
		if (condition !== undefined) return condition;

		const type = this._resolveExternalType(this.externalType);

		// For `import()` externals, keep them in the initial chunk to avoid loading
		// them asynchronously twice and to improve runtime performance.
		if (["css-import", "module"].includes(type)) {
			return true;
		}
		return compilation.chunkGraph.getNumberOfEntryModules(chunk) > 0;
	}

	/**
	 * Returns the unique identifier used to reference this module.
	 * @returns {string} a unique identifier of the module
	 */
	identifier() {
		return `external ${this._resolveExternalType(this.externalType)} ${JSON.stringify(this.request)}`;
	}

	/**
	 * Returns a human-readable identifier for this module.
	 * @param {RequestShortener} requestShortener the request shortener
	 * @returns {string} a user readable identifier of the module
	 */
	readableIdentifier(requestShortener) {
		return `external ${JSON.stringify(this.request)}`;
	}

	/**
	 * Checks whether the module needs to be rebuilt for the current build state.
	 * @param {NeedBuildContext} context context info
	 * @param {NeedBuildCallback} callback callback function, returns true, if the module needs a rebuild
	 * @returns {void}
	 */
	needBuild(context, callback) {
		return callback(null, !this.buildMeta);
	}

	/**
	 * Builds the module using the provided compilation context.
	 * @param {WebpackOptions} options webpack options
	 * @param {Compilation} compilation the compilation
	 * @param {ResolverWithOptions} resolver the resolver
	 * @param {InputFileSystem} fs the file system
	 * @param {BuildCallback} callback callback function
	 * @returns {void}
	 */
	build(options, compilation, resolver, fs, callback) {
		this.buildMeta = {
			async: false,
			exportsType: undefined
		};
		this.buildInfo = {
			strict: true,
			topLevelDeclarations: new Set(),
			javascriptModule: compilation.outputOptions.module
		};
		const { request, externalType } = this._getRequestAndExternalType();
		this.buildMeta.exportsType = "dynamic";
		let canMangle = false;
		this.clearDependenciesAndBlocks();
		switch (externalType) {
			case "this":
				this.buildInfo.strict = false;
				break;
			case "system":
				if (!Array.isArray(request) || request.length === 1) {
					this.buildMeta.exportsType = "namespace";
					canMangle = true;
				}
				break;
			case "module":
				if (this.buildInfo.javascriptModule) {
					if (!Array.isArray(request) || request.length === 1) {
						this.buildMeta.exportsType = "namespace";
						canMangle = true;
					}
				} else {
					this.buildMeta.async = true;
					EnvironmentNotSupportAsyncWarning.check(
						this,
						compilation.runtimeTemplate,
						"external module"
					);
					if (!Array.isArray(request) || request.length === 1) {
						this.buildMeta.exportsType = "namespace";
						canMangle = false;
					}
				}
				break;
			case "script":
				this.buildMeta.async = true;
				EnvironmentNotSupportAsyncWarning.check(
					this,
					compilation.runtimeTemplate,
					"external script"
				);
				break;
			case "promise":
				this.buildMeta.async = true;
				EnvironmentNotSupportAsyncWarning.check(
					this,
					compilation.runtimeTemplate,
					"external promise"
				);
				break;
			case "import":
				this.buildMeta.async = true;
				EnvironmentNotSupportAsyncWarning.check(
					this,
					compilation.runtimeTemplate,
					"external import"
				);
				if (!Array.isArray(request) || request.length === 1) {
					this.buildMeta.exportsType = "namespace";
					canMangle = false;
				}
				break;
		}
		this.addDependency(new StaticExportsDependency(true, canMangle));
		callback();
	}

	/**
	 * restore unsafe cache data
	 * @param {UnsafeCacheData} unsafeCacheData data from getUnsafeCacheData
	 * @param {NormalModuleFactory} normalModuleFactory the normal module factory handling the unsafe caching
	 */
	restoreFromUnsafeCache(unsafeCacheData, normalModuleFactory) {
		this._restoreFromUnsafeCache(unsafeCacheData, normalModuleFactory);
	}

	/**
	 * Returns the reason this module cannot be concatenated, when one exists.
	 * @param {ConcatenationBailoutReasonContext} context context
	 * @returns {string | undefined} reason why this module can't be concatenated, undefined when it can be concatenated
	 */
	getConcatenationBailoutReason(context) {
		switch (this.externalType) {
			case "amd":
			case "amd-require":
			case "umd":
			case "umd2":
			case "system":
			case "jsonp":
				return `${this.externalType} externals can't be concatenated`;
		}
		return undefined;
	}

	/**
	 * Get request and external type.
	 * @private
	 * @returns {{ request: string | string[], externalType: ExternalsType }} the request and external type
	 */
	_getRequestAndExternalType() {
		let { request, externalType } = this;
		if (typeof request === "object" && !Array.isArray(request)) {
			request = request[externalType];
		}
		externalType = this._resolveExternalType(externalType);
		return { request, externalType };
	}

	/**
	 * Resolve the detailed external type from the raw external type.
	 * e.g. resolve "module" or "import" from "module-import" type
	 * @param {ExternalsType} externalType raw external type
	 * @returns {ExternalsType} resolved external type
	 */
	_resolveExternalType(externalType) {
		if (externalType === "module-import") {
			if (
				this.dependencyMeta &&
				/** @type {ImportDependencyMeta} */
				(this.dependencyMeta).externalType
			) {
				return /** @type {ImportDependencyMeta} */ (this.dependencyMeta)
					.externalType;
			}
			return "module";
		} else if (externalType === "asset") {
			if (
				this.dependencyMeta &&
				/** @type {AssetDependencyMeta} */
				(this.dependencyMeta).sourceType
			) {
				return /** @type {AssetDependencyMeta} */ (this.dependencyMeta)
					.sourceType;
			}

			return "asset";
		}

		return externalType;
	}

	/**
	 * Returns the source data.
	 * @private
	 * @param {string | string[]} request request
	 * @param {ExternalsType} externalType the external type
	 * @param {RuntimeTemplate} runtimeTemplate the runtime template
	 * @param {ModuleGraph} moduleGraph the module graph
	 * @param {ChunkGraph} chunkGraph the chunk graph
	 * @param {RuntimeSpec} runtime the runtime
	 * @param {DependencyMeta | undefined} dependencyMeta the dependency meta
	 * @param {ConcatenationScope=} concatenationScope concatenationScope
	 * @returns {SourceData} the source data
	 */
	_getSourceData(
		request,
		externalType,
		runtimeTemplate,
		moduleGraph,
		chunkGraph,
		runtime,
		dependencyMeta,
		concatenationScope
	) {
		switch (externalType) {
			case "this":
			case "window":
			case "self":
				return getSourceForGlobalVariableExternal(request, this.externalType);
			case "global":
				return getSourceForGlobalVariableExternal(
					request,
					runtimeTemplate.globalObject
				);
			case "commonjs":
			case "commonjs2":
			case "commonjs-module":
			case "commonjs-static":
				return getSourceForCommonJsExternal(request);
			case "node-commonjs":
				return /** @type {BuildInfo} */ (this.buildInfo).javascriptModule
					? getSourceForCommonJsExternalInNodeModule(request, runtimeTemplate)
					: getSourceForCommonJsExternal(request);
			case "amd":
			case "amd-require":
			case "umd":
			case "umd2":
			case "system":
			case "jsonp": {
				const id = chunkGraph.getModuleId(this);
				return getSourceForAmdOrUmdExternal(
					id !== null ? id : this.identifier(),
					this.isOptional(moduleGraph),
					request,
					runtimeTemplate
				);
			}
			case "import":
				return getSourceForImportExternal(
					request,
					runtimeTemplate,
					/** @type {ImportDependencyMeta} */ (dependencyMeta)
				);
			case "script":
				return getSourceForScriptExternal(request, runtimeTemplate);
			case "module": {
				if (!(/** @type {BuildInfo} */ (this.buildInfo).javascriptModule)) {
					if (!runtimeTemplate.supportsDynamicImport()) {
						throw new Error(
							`The target environment doesn't support dynamic import() syntax so it's not possible to use external type 'module' within a script${
								runtimeTemplate.supportsEcmaScriptModuleSyntax()
									? "\nDid you mean to build a EcmaScript Module ('output.module: true')?"
									: ""
							}`
						);
					}
					return getSourceForImportExternal(
						request,
						runtimeTemplate,
						/** @type {ImportDependencyMeta} */ (dependencyMeta)
					);
				}
				if (!runtimeTemplate.supportsEcmaScriptModuleSyntax()) {
					throw new Error(
						"The target environment doesn't support EcmaScriptModule syntax so it's not possible to use external type 'module'"
					);
				}
				return getSourceForModuleExternal(
					request,
					moduleGraph.getExportsInfo(this),
					runtime,
					runtimeTemplate,
					/** @type {ImportDependencyMeta} */ (dependencyMeta),
					concatenationScope
				);
			}
			case "var":
			case "promise":
			case "assign":
			default:
				return getSourceForDefaultCase(
					this.isOptional(moduleGraph),
					request,
					runtimeTemplate
				);
		}
	}

	/**
	 * Generates code and runtime requirements for this module.
	 * @param {CodeGenerationContext} context context for code generation
	 * @returns {CodeGenerationResult} result
	 */
	codeGeneration({
		runtimeTemplate,
		moduleGraph,
		chunkGraph,
		runtime,
		concatenationScope
	}) {
		const { request, externalType } = this._getRequestAndExternalType();
		switch (externalType) {
			case "asset": {
				/** @type {Sources} */
				const sources = new Map();
				sources.set(
					JAVASCRIPT_TYPE,
					new RawSource(`module.exports = ${JSON.stringify(request)};`)
				);
				/** @type {CodeGenerationResultData} */
				const data = new Map();
				data.set("url", { javascript: /** @type {string} */ (request) });
				return { sources, runtimeRequirements: RUNTIME_REQUIREMENTS, data };
			}
			case "css-url": {
				/** @type {Sources} */
				const sources = new Map();
				/** @type {CodeGenerationResultData} */
				const data = new Map();
				data.set("url", { "css-url": /** @type {string} */ (request) });
				return { sources, runtimeRequirements: RUNTIME_REQUIREMENTS, data };
			}
			case "css-import": {
				/** @type {Sources} */
				const sources = new Map();
				const dependencyMeta = /** @type {CssImportDependencyMeta} */ (
					this.dependencyMeta
				);
				const layer =
					dependencyMeta.layer !== undefined
						? ` layer(${dependencyMeta.layer})`
						: "";
				const supports = dependencyMeta.supports
					? ` supports(${dependencyMeta.supports})`
					: "";
				const media = dependencyMeta.media ? ` ${dependencyMeta.media}` : "";
				sources.set(
					"css-import",
					new RawSource(
						`@import url(${JSON.stringify(
							request
						)})${layer}${supports}${media};`
					)
				);
				return {
					sources,
					runtimeRequirements: EMPTY_RUNTIME_REQUIREMENTS
				};
			}
			default: {
				const sourceData = this._getSourceData(
					request,
					externalType,
					runtimeTemplate,
					moduleGraph,
					chunkGraph,
					runtime,
					this.dependencyMeta,
					concatenationScope
				);

				// sourceString can be empty str only when there is concatenationScope
				let sourceString = sourceData.expression;
				if (sourceData.iife) {
					sourceString = `(function() { return ${sourceString}; }())`;
				}

				const specifiers = sourceData.specifiers;
				if (specifiers) {
					sourceString = "";
					const scope = /** @type {ConcatenationScope} */ (concatenationScope);
					for (const [specifier, finalName] of specifiers) {
						scope.registerRawExport(specifier, finalName);
					}
				} else if (concatenationScope) {
					sourceString = `${runtimeTemplate.renderConst()} ${ConcatenationScope.NAMESPACE_OBJECT_EXPORT} = ${sourceString};`;
					concatenationScope.registerNamespaceExport(
						ConcatenationScope.NAMESPACE_OBJECT_EXPORT
					);
				} else {
					sourceString = `module.exports = ${sourceString};`;
				}
				if (sourceData.init) {
					sourceString = `${sourceData.init}\n${sourceString}`;
				}

				/** @type {undefined | CodeGenerationResultData} */
				let data;
				if (sourceData.chunkInitFragments) {
					data = new Map();
					data.set("chunkInitFragments", sourceData.chunkInitFragments);
				}

				/** @type {Sources} */
				const sources = new Map();
				if (this.useSourceMap || this.useSimpleSourceMap) {
					sources.set(
						JAVASCRIPT_TYPE,
						new OriginalSource(sourceString, this.identifier())
					);
				} else {
					sources.set(JAVASCRIPT_TYPE, new RawSource(sourceString));
				}

				let runtimeRequirements = sourceData.runtimeRequirements;
				if (!concatenationScope) {
					if (!runtimeRequirements) {
						runtimeRequirements = RUNTIME_REQUIREMENTS;
					} else {
						const set = new Set(runtimeRequirements);
						set.add(RuntimeGlobals.module);
						runtimeRequirements = set;
					}
				}

				return {
					sources,
					runtimeRequirements:
						runtimeRequirements || EMPTY_RUNTIME_REQUIREMENTS,
					data
				};
			}
		}
	}

	/**
	 * Returns the estimated size for the requested source type.
	 * @param {string=} type the source type for which the size should be estimated
	 * @returns {number} the estimated size of the module (must be non-zero)
	 */
	size(type) {
		return 42;
	}

	/**
	 * Updates the hash with the data contributed by this instance.
	 * @param {Hash} hash the hash used to track dependencies
	 * @param {UpdateHashContext} context context
	 * @returns {void}
	 */
	updateHash(hash, context) {
		const { chunkGraph } = context;
		hash.update(
			`${this._resolveExternalType(this.externalType)}${JSON.stringify(this.request)}${this.isOptional(
				chunkGraph.moduleGraph
			)}`
		);
		super.updateHash(hash, context);
	}

	/**
	 * Serializes this instance into the provided serializer context.
	 * @param {ObjectSerializerContext} context context
	 */
	serialize(context) {
		const { write } = context;

		write(this.request);
		write(this.externalType);
		write(this.userRequest);
		write(this.dependencyMeta);

		super.serialize(context);
	}

	/**
	 * Restores this instance from the provided deserializer context.
	 * @param {ObjectDeserializerContext} context context
	 */
	deserialize(context) {
		const { read } = context;

		this.request = read();
		this.externalType = read();
		this.userRequest = read();
		this.dependencyMeta = read();

		super.deserialize(context);
	}
}

makeSerializable(ExternalModule, "webpack/lib/ExternalModule");

module.exports = ExternalModule;
module.exports.ModuleExternalInitFragment = ModuleExternalInitFragment;
module.exports.getExternalModuleNodeCommonjsInitFragment =
	getExternalModuleNodeCommonjsInitFragment;