@vitejs/plugin-legacy: __vite_legacy_guard error with systemjs and single-spa

[adrianorob90]

Describe the bug

I made a single-spa-application with Vite and Svelte. The bundle in Systemjs format contains an error due to the presence of the __vite_legacy_guard export, without it everything works correctly. An option to disable __vite_legacy_guard would be useful.

Reproduction

https://github.com/adrianorob90/svelte-skeleton-vite

Steps to reproduce

npm i 
npm run build

After open the file
dist/20/svelte-skeleton/js/svelte-skeleton-main.0.1.0.js

System Info

System:
    OS: macOS 12.2.1
    CPU: (8) arm64 Apple M1 Pro
    Memory: 63.80 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.15.0 - ~/.nvm/versions/node/v16.15.0/bin/node
    Yarn: 1.22.15 - ~/.nvm/versions/node/v16.15.0/bin/yarn
    npm: 8.5.5 - ~/.nvm/versions/node/v16.15.0/bin/npm
  Browsers:
    Chrome: 109.0.5414.119
    Safari: 15.3
  npmPackages:
    @vitejs/plugin-legacy: ^4.0.1 => 4.0.1 
    vite: ^4.1.0 => 4.1.1

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[bluwy]

The main non-legacy (or modern) chunk shouldn't be a systemjs file by default unless you change that? If so, it wouldn't work as plugin-legacy expects the modern chunk to be ESM. If not, a repro would help dissect the issue.

[github-actions]

Hello @adrianorob90. Please provide a minimal reproduction using a GitHub repository or StackBlitz. Issues marked with need reproduction will be closed if they have no activity within 3 days.

[adrianorob90]

hi @bluwy I added a link to the repo to reproduce the error :)

[patak-dev]

As @bluwy said in his prev message, you shouldn't change to systemjs for the main build here

[adrianorob90]

Hi @patak-dev I need the systemjs version to load the project in the single-spa root project. Alternatively how can I do it?

[bluwy]

You need to use plugin-legacy if you need systemjs. If you need that format only, you can follow #10139 so it's configurable to ship systemjs only.