fix: types and tests

declarations/WebpackOptions.d.ts

@@ -3175,7 +3175,7 @@ export interface ExternalItemFunctionData {
 		| ((
 				context: string,
 				request: string,
-				callback: (err?: Error, result?: string) => void
+				callback: (err?: Error | null, result?: string | false) => void
 		  ) => void)
 		| ((context: string, request: string) => Promise<string>);
 	/**

lib/ExternalModuleFactoryPlugin.js

@@ -15,10 +15,13 @@ const ImportDependency = require("./dependencies/ImportDependency");
 const { resolveByProperty, cachedSetProperty } = require("./util/cleverMerge");
 
 /** @typedef {import("../declarations/WebpackOptions").ExternalItemFunctionData} ExternalItemFunctionData */
+/** @typedef {import("../declarations/WebpackOptions").ExternalItemObjectKnown} ExternalItemObjectKnown */
+/** @typedef {import("../declarations/WebpackOptions").ExternalItemObjectUnknown} ExternalItemObjectUnknown */
 /** @typedef {import("../declarations/WebpackOptions").Externals} Externals */
 /** @typedef {import("./Compilation").DepConstructor} DepConstructor */
 /** @typedef {import("./ExternalModule").DependencyMeta} DependencyMeta */
 /** @typedef {import("./Module")} Module */
+/** @typedef {import("./ModuleFactory").IssuerLayer} IssuerLayer */
 /** @typedef {import("./NormalModuleFactory")} NormalModuleFactory */
 
 const UNSPECIFIED_EXTERNAL_TYPE_REGEXP = /^[a-z0-9-]+ /;
@@ -27,7 +30,7 @@ const EMPTY_RESOLVE_OPTIONS = {};
 // TODO webpack 6 remove this
 const callDeprecatedExternals = util.deprecate(
 	/**
-	 * @param {TODO} externalsFunction externals function
+	 * @param {EXPECTED_FUNCTION} externalsFunction externals function
 	 * @param {string} context context
 	 * @param {string} request request
 	 * @param {(err: Error | null | undefined, value: ExternalValue | undefined, ty: ExternalType | undefined) => void} cb cb
@@ -40,19 +43,26 @@ const callDeprecatedExternals = util.deprecate(
 	"DEP_WEBPACK_EXTERNALS_FUNCTION_PARAMETERS"
 );
 
+/** @typedef {ExternalItemObjectKnown & ExternalItemObjectUnknown} ExternalItemObject */
+
+/**
+ * @template {ExternalItemObject} T
+ * @typedef {WeakMap<T, Map<IssuerLayer, Omit<T, "byLayer">>>} ExternalWeakCache
+ */
+
+/** @type {ExternalWeakCache<ExternalItemObject>} */
 const cache = new WeakMap();
 
 /**
- * @template {object} T
+ * @param {ExternalItemObject} obj obj
- * @param {T} obj obj
+ * @param {IssuerLayer} layer layer
- * @param {TODO} layer layer
+ * @returns {Omit<ExternalItemObject, "byLayer">} result
- * @returns {Omit<T, "byLayer">} result
  */
 const resolveLayer = (obj, layer) => {
-	let map = cache.get(/** @type {object} */ (obj));
+	let map = cache.get(obj);
 	if (map === undefined) {
 		map = new Map();
-		cache.set(/** @type {object} */ (obj), map);
+		cache.set(obj, map);
 	} else {
 		const cacheEntry = map.get(layer);
 		if (cacheEntry !== undefined) return cacheEntry;
@@ -275,8 +285,7 @@ class ExternalModuleFactoryPlugin {
 												context,
 												request,
 												resolveContext,
-												/** @type {TODO} */
+												callback
-												(callback)
 											);
 										} else {
 											return new Promise((resolve, reject) => {
@@ -302,7 +311,8 @@ class ExternalModuleFactoryPlugin {
 					} else if (typeof externals === "object") {
 						const resolvedExternals = resolveLayer(
 							externals,
-							contextInfo.issuerLayer
+							/** @type {IssuerLayer} */
+							(contextInfo.issuerLayer)
 						);
 						if (
 							Object.prototype.hasOwnProperty.call(

lib/ModuleFactory.js

@@ -18,11 +18,13 @@
  * @property {boolean=} cacheable allow to use the unsafe cache
  */
 
+/** @typedef {string | null} IssuerLayer */
+
 /**
  * @typedef {object} ModuleFactoryCreateDataContextInfo
  * @property {string} issuer
- * @property {string | null=} issuerLayer
+ * @property {IssuerLayer=} issuerLayer
- * @property {string} compiler
+ * @property {string=} compiler
  */
 
 /**

schemas/WebpackOptions.json

@@ -1206,7 +1206,7 @@
         "getResolve": {
           "description": "Get a resolve function with the current resolver options.",
           "instanceof": "Function",
-          "tsType": "((options?: ResolveOptions) => ((context: string, request: string, callback: (err?: Error, result?: string) => void) => void) | ((context: string, request: string) => Promise<string>))"
+          "tsType": "((options?: ResolveOptions) => ((context: string, request: string, callback: (err?: Error | null, result?: string | false) => void) => void) | ((context: string, request: string) => Promise<string>))"
         },
         "request": {
           "description": "The request as written by the user in the require/import expression/statement.",

test/configCases/externals/resolve-callback/index.js

@@ -0,0 +1,7 @@
+it("should allow functions as externals with promise and resolver", function () {
+	const result = require("external");
+	expect(result).toMatch(/^[a-z]:\\|\//i);
+	expect(result).toMatch(/resolve-callback.node_modules.external\.js$/);
+	const result1 = require("external-false");
+	expect(JSON.stringify(result1)).toBe('{}');
+});

test/configCases/externals/resolve-callback/webpack.config.js

@@ -0,0 +1,28 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	optimization: {
+		concatenateModules: true
+	},
+	externals: [
+		({ context, request, getResolve }, callback) => {
+			if (request !== "external" && request !== "external-false") {
+				return callback(null, false);
+			}
+
+			const resolve = getResolve({
+				alias: {
+					"external-false": false
+				}
+			});
+
+			if (request === "external-false") {
+				resolve(context, request, callback);
+			} else {
+				resolve(context, request, (err, resolved) => {
+					if (err) callback(err);
+					else callback(null, `var ${JSON.stringify(resolved)}`);
+				});
+			}
+		}
+	]
+};

test/configCases/externals/resolve/index.js

@@ -2,4 +2,7 @@ it("should allow functions as externals with promise and resolver", function ()
 	const result = require("external");
 	expect(result).toMatch(/^[a-z]:\\|\//i);
 	expect(result).toMatch(/resolve.node_modules.external\.js$/);
+	const result2 = require("external-promise");
+	expect(result2).toMatch(/^[a-z]:\\|\//i);
+	expect(result2).toMatch(/resolve.node_modules.external-promise\.js$/);
 });

test/configCases/externals/resolve/webpack.config.js

@@ -5,7 +5,10 @@ module.exports = {
 	},
 	externals: [
 		async ({ context, request, getResolve }) => {
-			if (request !== "external") return false;
+			if (request !== "external" && request !== "external-promise") {
+				return false;
+			}
+
 			const resolve = getResolve();
 			const resolved = await resolve(context, request);
 			return `var ${JSON.stringify(resolved)}`;

types.d.ts

@@ -4791,7 +4791,7 @@ declare interface ExternalItemFunctionData {
 		| ((
 				context: string,
 				request: string,
-				callback: (err?: Error, result?: string) => void
+				callback: (err?: null | Error, result?: string | false) => void
 		  ) => void)
 		| ((context: string, request: string) => Promise<string>);
 
@@ -9026,7 +9026,7 @@ declare interface ModuleFactoryCreateData {
 declare interface ModuleFactoryCreateDataContextInfo {
 	issuer: string;
 	issuerLayer?: null | string;
-	compiler: string;
+	compiler?: string;
 }
 declare interface ModuleFactoryResult {
 	/**