Vite 4.4.10 - iife modules that import certain libraries break at runtime

[kadoshms]

Describe the bug

Since this commit was introduced as part of 4.4.10, iife modules that import certain libraries started breaking on runtime with exceptions such as:

Uncaught SyntaxError: Illegal return statement (at

In our case, we used the qs library - https://www.npmjs.com/package/qs, simply importing them into an IIFE module, and even printing the library contents reproduces the issue.

In particular, the issue comes from the following manipulation on the code during build:

                    const esbuildHelpers = esbuildCode.slice(0, contentIndex);
                    res.code = esbuildCode
                        .slice(contentIndex)
                        .replace(`"use strict";`, `"use strict";` + esbuildHelpers);

I guess that since qs compiles with commonjs might be the issue.
However, we have been using this library with our IIFE modules for months now, and this issue started popping out, unfortunately on runtime, only since we upgraded to 4.4.10.

Reproduction

https://stackblitz.com/edit/vitejs-vite-su78z8?file=main.js,vite.config.ts,index.ts,index.html,package.json,node_modules%2Fvite%2Fdist%2Fnode%2Fchunks%2Fdep-3bba9c7e.js&terminal=dev

Steps to reproduce

Simply run the project.
To "fix", remove the console.log from index.ts

System Info

This reproduces easily on the StackBlitz, but anyway:


  System:
    OS: macOS 13.6
    CPU: (12) arm64 Apple M2 Pro
    Memory: 1.71 GB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 16.20.1 - ~/.nvm/versions/node/v16.20.1/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 8.19.4 - ~/.nvm/versions/node/v16.20.1/bin/npm
    pnpm: 8.6.10 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 117.0.5938.132
    Safari: 17.0
  npmPackages:
    @vitejs/plugin-react: ^4.1.0 => 4.1.0 
    vite: ^4.4.10 => 4.4.10

Used Package Manager

yarn

Logs

No response

Validations

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[bluwy]

Vite 4.4.11 is published which reverts 128ad8f, will keep it open for now as the bug still exist in Vite 5.

[kadoshms]

Thanks for that @bluwy