fix: use rel modulepreload for esm modules

lib/web/JsonpChunkLoadingRuntimeModule.js

@@ -250,17 +250,19 @@ class JsonpChunkLoadingRuntimeModule extends RuntimeModule {
 							linkPreload.call(
 								Template.asString([
 									"var link = document.createElement('link');",
-									scriptType
-										? `link.type = ${JSON.stringify(scriptType)};`
-										: "",
+									scriptType === "module"
+										? ""
+										: `link.type = ${JSON.stringify(scriptType)};`,
 									"link.charset = 'utf-8';",
 									`if (${RuntimeGlobals.scriptNonce}) {`,
 									Template.indent(
 										`link.setAttribute("nonce", ${RuntimeGlobals.scriptNonce});`
 									),
 									"}",
-									'link.rel = "preload";',
-									'link.as = "script";',
+									scriptType === "module"
+										? 'link.rel = "modulepreload";'
+										: 'link.rel = "preload";',
+									scriptType === "module" ? "" : 'link.as = "script";',
 									`link.href = ${RuntimeGlobals.publicPath} + ${RuntimeGlobals.getChunkScriptFilename}(chunkId);`,
 									crossOriginLoading
 										? crossOriginLoading === "use-credentials"

test/configCases/web/prefetch-preload-module/chunk1.js

@@ -0,0 +1,5 @@
+export default function() {
+	import(/* webpackPrefetch: true, webpackChunkName: "chunk1-a" */ "./chunk1-a");
+	import(/* webpackPreload: true, webpackChunkName: "chunk1-b" */ "./chunk1-b");
+	import(/* webpackPrefetch: 10, webpackChunkName: "chunk1-c" */ "./chunk1-c");
+}

test/configCases/web/prefetch-preload-module/chunk2.js

@@ -0,0 +1,4 @@
+export default function() {
+	import(/* webpackPrefetch: true, webpackChunkName: "chunk1-a" */ "./chunk1-a");
+	import(/* webpackPreload: true, webpackChunkName: "chunk1-b" */ "./chunk1-b");
+}

test/configCases/web/prefetch-preload-module/index.js

@@ -0,0 +1,90 @@
+// This config need to be set on initial evaluation to be effective
+__webpack_nonce__ = "nonce";
+__webpack_public_path__ = "https://example.com/public/path/";
+
+it("should prefetch and preload child chunks on chunk load", () => {
+	let link, script;
+
+	expect(document.head._children).toHaveLength(1);
+
+	// Test prefetch from entry chunk
+	link = document.head._children[0];
+	expect(link._type).toBe("link");
+	expect(link.rel).toBe("prefetch");
+	expect(link.href).toBe("https://example.com/public/path/chunk1.js");
+
+	const promise = import(
+		/* webpackChunkName: "chunk1", webpackPrefetch: true */ "./chunk1"
+	);
+
+	expect(document.head._children).toHaveLength(3);
+
+	// Test normal script loading
+	script = document.head._children[1];
+	expect(script._type).toBe("script");
+	expect(script.src).toBe("https://example.com/public/path/chunk1.js");
+	expect(script.getAttribute("nonce")).toBe("nonce");
+	expect(script.crossOrigin).toBe("anonymous");
+	expect(script.onload).toBeTypeOf("function");
+
+	// Test preload of chunk1-b
+	link = document.head._children[2];
+	expect(link._type).toBe("link");
+	expect(link.rel).toBe("preload");
+	expect(link.as).toBe("script");
+	expect(link.href).toBe("https://example.com/public/path/chunk1-b.js");
+	expect(link.charset).toBe("utf-8");
+	expect(link.getAttribute("nonce")).toBe("nonce");
+	expect(link.crossOrigin).toBe("anonymous");
+
+	// Run the script
+	__non_webpack_require__("./chunk1.js");
+
+	script.onload();
+
+	return promise.then(() => {
+		expect(document.head._children).toHaveLength(4);
+
+		// Test prefetching for chunk1-c and chunk1-a in this order
+		link = document.head._children[2];
+		expect(link._type).toBe("link");
+		expect(link.rel).toBe("prefetch");
+		expect(link.href).toBe("https://example.com/public/path/chunk1-c.js");
+		expect(link.crossOrigin).toBe("anonymous");
+
+		link = document.head._children[3];
+		expect(link._type).toBe("link");
+		expect(link.rel).toBe("prefetch");
+		expect(link.href).toBe("https://example.com/public/path/chunk1-a.js");
+		expect(link.crossOrigin).toBe("anonymous");
+
+		const promise2 = import(
+			/* webpackChunkName: "chunk1", webpackPrefetch: true */ "./chunk1"
+		);
+
+		// Loading chunk1 again should not trigger prefetch/preload
+		expect(document.head._children).toHaveLength(4);
+
+		const promise3 = import(/* webpackChunkName: "chunk2" */ "./chunk2");
+
+		expect(document.head._children).toHaveLength(5);
+
+		// Test normal script loading
+		script = document.head._children[4];
+		expect(script._type).toBe("script");
+		expect(script.src).toBe("https://example.com/public/path/chunk2.js");
+		expect(script.getAttribute("nonce")).toBe("nonce");
+		expect(script.crossOrigin).toBe("anonymous");
+		expect(script.onload).toBeTypeOf("function");
+
+		// Run the script
+		__non_webpack_require__("./chunk2.js");
+
+		script.onload();
+
+		return promise3.then(() => {
+			// Loading chunk2 again should not trigger prefetch/preload as it's already prefetch/preloaded
+			expect(document.head._children).toHaveLength(4);
+		});
+	});
+});

test/configCases/web/prefetch-preload-module/index.mjs

@@ -0,0 +1,89 @@
+// This config need to be set on initial evaluation to be effective
+__webpack_nonce__ = "nonce";
+__webpack_public_path__ = "https://example.com/public/path/";
+
+it("should prefetch and preload child chunks on chunk load", () => {
+	let link, script;
+
+	expect(document.head._children).toHaveLength(1);
+
+	// Test prefetch from entry chunk
+	link = document.head._children[0];
+	expect(link._type).toBe("link");
+	expect(link.rel).toBe("prefetch");
+	expect(link.href).toBe("https://example.com/public/path/chunk1.js");
+
+	const promise = import(
+		/* webpackChunkName: "chunk1", webpackPrefetch: true */ "./chunk1.js"
+	);
+
+	expect(document.head._children).toHaveLength(3);
+
+	// Test normal script loading
+	script = document.head._children[1];
+	expect(script._type).toBe("script");
+	expect(script.src).toBe("https://example.com/public/path/chunk1.js");
+	expect(script.getAttribute("nonce")).toBe("nonce");
+	expect(script.crossOrigin).toBe("anonymous");
+	expect(script.onload).toBeTypeOf("function");
+
+	// Test preload of chunk1-b
+	link = document.head._children[2];
+	expect(link._type).toBe("link");
+	expect(link.rel).toBe("modulepreload");
+	expect(link.href).toBe("https://example.com/public/path/chunk1-b.js");
+	expect(link.charset).toBe("utf-8");
+	expect(link.getAttribute("nonce")).toBe("nonce");
+	expect(link.crossOrigin).toBe("anonymous");
+
+	// Run the script
+	__non_webpack_require__("./chunk1.js");
+
+	script.onload();
+
+	return promise.then(() => {
+		expect(document.head._children).toHaveLength(4);
+
+		// Test prefetching for chunk1-c and chunk1-a in this order
+		link = document.head._children[2];
+		expect(link._type).toBe("link");
+		expect(link.rel).toBe("prefetch");
+		expect(link.href).toBe("https://example.com/public/path/chunk1-c.js");
+		expect(link.crossOrigin).toBe("anonymous");
+
+		link = document.head._children[3];
+		expect(link._type).toBe("link");
+		expect(link.rel).toBe("prefetch");
+		expect(link.href).toBe("https://example.com/public/path/chunk1-a.js");
+		expect(link.crossOrigin).toBe("anonymous");
+
+		const promise2 = import(
+			/* webpackChunkName: "chunk1", webpackPrefetch: true */ "./chunk1.js"
+		);
+
+		// Loading chunk1 again should not trigger prefetch/preload
+		expect(document.head._children).toHaveLength(4);
+
+		const promise3 = import(/* webpackChunkName: "chunk2" */ "./chunk2.js");
+
+		expect(document.head._children).toHaveLength(5);
+
+		// Test normal script loading
+		script = document.head._children[4];
+		expect(script._type).toBe("script");
+		expect(script.src).toBe("https://example.com/public/path/chunk2.js");
+		expect(script.getAttribute("nonce")).toBe("nonce");
+		expect(script.crossOrigin).toBe("anonymous");
+		expect(script.onload).toBeTypeOf("function");
+
+		// Run the script
+		__non_webpack_require__("./chunk2.js");
+
+		script.onload();
+
+		return promise3.then(() => {
+			// Loading chunk2 again should not trigger prefetch/preload as it's already prefetch/preloaded
+			expect(document.head._children).toHaveLength(4);
+		});
+	});
+});

test/configCases/web/prefetch-preload-module/webpack.config.js

@@ -0,0 +1,22 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	entry: "./index.mjs",
+	experiments: {
+		outputModule: true
+	},
+	name: "esm",
+	target: "web",
+	output: {
+		publicPath: "",
+		module: true,
+		filename: "bundle0.js",
+		chunkFilename: "[name].js",
+		crossOriginLoading: "anonymous"
+	},
+	performance: {
+		hints: false
+	},
+	optimization: {
+		minimize: false
+	}
+};