Dev(or serve) mode doesn't compatible with amd format.

[FoxDaxian]

Describe the bug

Use system0.21.6 to load main.jsx instead use type:module to load, shown as below:

Then use @babel/plugin-transform-modules-amd to transform source files so that SystemJS.import can work, shown as below:

Inspect page, what main.jsx shows is:

You can see except React an React-DOM which we can inject into html manually or automatically, and use SystemJS.register to initialize them. we have another dependence, named ./App.jsx, that means if we have 5 dependencies. we need use SystemJS.register to register them one by one. that's not what I want.

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So I think Vite should bundle all code of src folder into to one single file(maybe main.jsx) when serve mode.

Hope can get your responses as soon as possible.
Best regards.

Reproduction

https://stackblitz.com/edit/vitejs-vite-wzmngy?file=vite.config.js

Steps to reproduce

just open stackblitz, then inspect page, check the network.

System Info

System:
    OS: macOS 13.6.6
    CPU: (8) arm64 Apple M1 Pro
    Memory: 62.73 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.20.2 - ~/.nvm/versions/node/v18.20.2/bin/node
    npm: 10.5.0 - ~/.nvm/versions/node/v18.20.2/bin/npm
    pnpm: 8.10.3 - ~/.nvm/versions/node/v18.20.2/bin/pnpm
  Browsers:
    Chrome: 124.0.6367.62
    Safari: 16.6
  npmPackages:
    @vitejs/plugin-react: ^4.2.1 => 4.2.1 
    vite: ^5.2.0 => 5.2.9

Used Package Manager

npm

Logs

No response

Validations

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[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-wzmngy (Open reproduction)

[sapphi-red]

I think Vite should bundle all code of src folder into to one single file(maybe main.jsx) when serve mode.

This is in direct conflict with Vite's philosophy, so I don't think it will be implemented.
https://vitejs.dev/guide/why.html#slow-server-start

But probably you would be able to swap ESM with SystemJS modules when #16471 lands. Although it would require quite a effort.