fix: __VITE_PRELOAD__ replacement error, fix #3051

[ygj6]

Description

fix #3051

When there is only one dynamic import, the input parameter deps of the preload function,

vite/packages/vite/src/node/plugins/importAnalysisBuild.ts

Lines 23 to 28 in 98d95e3

	/**
	* Helper for preloading CSS and direct imports of async chunks in parallel to
	* the async chunk itself.
	*/
	function preload(baseModule: () => Promise<{}>, deps?: string[]) {
	// @ts-ignore

when terser compresses for the third time, it will think that deps is a constant string, move directly to the place of call and delete the input parameters.

Before terser minify,complete file,before.txt:

import { o as openBlock, c as createBlock, a as createVNode, w as withCtx, b as createTextVNode, r as resolveComponent, d as createRouter, e as createWebHashHistory, f as createApp } from "./vendor.30acece7.js";
let scriptRel;
const seen = {};
const __vitePreload = function preload(baseModule, deps) {
  if (!deps) {
    return baseModule();
  }
  if (scriptRel === void 0) {
    const relList = document.createElement("link").relList;
    scriptRel = relList && relList.supports && relList.supports("modulepreload") ? "modulepreload" : "preload";
  }
  return Promise.all(deps.map((dep) => {
    ......
  })).then(() => baseModule());
};
......
const routes = [
  { path: "/", name: "Home", component: _sfc_main$1 },
  {
    path: "/about",
    name: "About",
    component: () => __vitePreload(() => import("./About.d4daf36e.js"), true ? "__VITE_PRELOAD__" : void 0)
  }
];
......

After terser minify,complete file,after.txt:

......
var E = a({
    routes: [ {
    ......
    }, {
        path: "/about",
        name: "About",
        component: () => function(e, t) {
           ......
            return Promise.all("__VITE_PRELOAD__".map((e => {
               ......
            }))).then((() => import("./About.d4daf36e.js")));
        }()
    } ],
    history: u()
});
......

The above behavior will cause the __VITE_PRELOAD__ marker to move from the back of the import statement to the front, causing the code.indexOf(preloadMarker, end) to not find the mark,resulting in no replacement of the __VITE_PRELOAD__

vite/packages/vite/src/node/plugins/importAnalysisBuild.ts

Lines 265 to 275 in 98d95e3

	const markPos = code.indexOf(preloadMarker, end)
	if (markPos > 0) {
	s.overwrite(
	markPos - 1,
	markPos + preloadMarker.length + 1,
	// the dep list includes the main chunk, so only need to
	// preload when there are actual other deps.
	deps.size > 1
	? `[${[...deps].map((d) => JSON.stringify(d)).join(',')}]`
	: `void 0`
	)

Finally, __VITE_PRELOAD__ was incorrectly replaced with void 0 by the following code

vite/packages/vite/src/node/plugins/importAnalysisBuild.ts

Lines 282 to 284 in 98d95e3

	// there may still be markers due to inlined dynamic imports, remove
	// all the markers regardless
	chunk.code = chunk.code.replace(preloadMarkerRE, 'void 0')

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
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