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fix: __VITE_PRELOAD__ replacement error, fix #3051 #4163

merged 5 commits into from Jul 8, 2021


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@ygj6 ygj6 commented Jul 7, 2021


fix #3051

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

* 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( => {
  })).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__

const markPos = code.indexOf(preloadMarker, end)
if (markPos > 0) {
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

// 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

Before submitting the PR, please make sure you do the following

  • Read the Contributing Guidelines.
  • Read the Pull Request Guidelines and follow the Commit Convention.
  • Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
  • Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
  • Ideally, include relevant tests that fail without this PR but pass with it.

@Shinigami92 Shinigami92 added the p3-minor-bug 🔨 An edge case that only affects very specific usage (priority) label Jul 7, 2021
ygj6 and others added 3 commits July 7, 2021 20:51
Co-authored-by: patak <>
Co-authored-by: patak <>
@patak-dev patak-dev requested a review from sodatea July 8, 2021 06:12
@sodatea sodatea merged commit d377aae into vitejs:main Jul 8, 2021
aleclarson pushed a commit to aleclarson/vite that referenced this pull request Nov 8, 2021
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p3-minor-bug 🔨 An edge case that only affects very specific usage (priority)
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Minifying the code in 3 passes leads to a syntax error
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