Add output.entryPrefetchFunction option, and don't immediately prefetch

Rather than calling the prefetch function on its own during bootstrap, this change exposes the function as a function that can be called from the compiled code.

lib/WebpackOptionsDefaulter.js

@@ -161,6 +161,11 @@ class WebpackOptionsDefaulter extends OptionsDefaulter {
 		this.set("output.hashDigestLength", 20);
 		this.set("output.devtoolLineToLine", false);
 		this.set("output.strictModuleExceptionHandling", false);
+		this.set("output.entryPrefetchFunction", "make", options => {
+			return Template.toIdentifier(
+				"webpackEntryPrefetch" + Template.toIdentifier(options.output.library)
+			);
+		});
 
 		this.set("node", "call", value => {
 			if (typeof value === "boolean") {

lib/web/JsonpMainTemplatePlugin.js

@@ -114,7 +114,7 @@ class JsonpMainTemplatePlugin {
 			});
 		};
 
-		const linkPreload = mainTemplate => {
+		const linkPreload = () => {
 			const crossOriginLoading = mainTemplate.outputOptions.crossOriginLoading;
 			const jsonpScriptType = mainTemplate.outputOptions.jsonpScriptType;
 			return Template.asString([
@@ -181,16 +181,19 @@ class JsonpMainTemplatePlugin {
 				}
 				if (needEntryChunkPrefetch(chunk)) {
 					let preloadPrefetchChildren = chunk.getChildIdsByOrders();
+					let entryPrefetchFunction = mainTemplate.outputOptions.entryPrefetchFunction;
+					let globalObject = mainTemplate.outputOptions.globalObject;
+
 					extraCode.push(
 						"",
 						"// preload or prefetch split chunks from entry chunk",
-						"(function prefetchOrPreloadFromEntry() {",
+						`${globalObject}['${entryPrefetchFunction}'] = () => {`,
 						preloadPrefetchChildren.preload
 							? Template.indent([
 									`${JSON.stringify(
 										preloadPrefetchChildren.preload
 									)}.map(chunkId => {`,
-									Template.indent([linkPreload(mainTemplate)]),
+									Template.indent([linkPreload()]),
 									`});`
 							  ])
 							: "",
@@ -203,7 +206,7 @@ class JsonpMainTemplatePlugin {
 									`});`
 							  ])
 							: "",
-						"})();"
+						"}",
 					);
 				}
 				if (extraCode.length === 0) return source;
@@ -271,7 +274,7 @@ class JsonpMainTemplatePlugin {
 		mainTemplate.hooks.linkPreload.tap(
 			"JsonpMainTemplatePlugin",
 			(_, chunk, hash) => {
-				return linkPreload(mainTemplate);
+				return linkPreload();
 			}
 		);
 		mainTemplate.hooks.linkPrefetch.tap(

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

@@ -21,7 +21,7 @@ it("should prefetch and preload child chunks on chunk load", (done) => {
 	__webpack_nonce__ = "nonce";
 	__webpack_public_path__ = "/public/path/";
 
-	const promise = import(/* webpackChunkName: "chunk1" */ "./chunk1");
+	const promise = import(/* webpackChunkName: "chunk1", webpackPrefetch: true */ "./chunk1");
 	expect(document.head._children).toHaveLength(2);
 	const script = document.head._children[0];
 	expect(script._type).toBe("script");