RefreshRuntime is not added when primitive return type

[nojaf]

Describe the bug

When returning a plain string from a function component, the fast refresh is not added.
While I believe React does consider this as a valid component.

function Foo(props) {
  return 'meh2';
}

let make = Foo;

export { make };

Reproduction

https://stackblitz.com/edit/vitejs-vite-wzbtgaex?file=src%2FFoo.js

Steps to reproduce

• npm i
• npm run dev
• Edit Foo.js (page reload)
• Edit Bar.js (hmr reload)

System Info

System:
    OS: macOS 15.3
    CPU: (16) arm64 Apple M4 Max
    Memory: 698.27 MB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.13.1 - ~/.nvm/versions/node/v22.13.1/bin/node
    npm: 10.9.2 - ~/.nvm/versions/node/v22.13.1/bin/npm
    pnpm: 9.15.5 - ~/.nvm/versions/node/v22.13.1/bin/pnpm
    bun: 1.2.2 - ~/.bun/bin/bun
  Browsers:
    Brave Browser: 133.1.75.178
    Chrome: 133.0.6943.99
    Safari: 18.3
  npmPackages:
    @vitejs/plugin-react: ^4.3.4 => 4.3.4 
    vite: ^6.1.0 => 6.1.0

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.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[hi-ogawa]

Closing as a duplicate of #402. See #402 (comment) for details.

You can workaround this by injecting a magic word "react/jsx-runtime" somewhere in the code (or via plugin): https://stackblitz.com/edit/vitejs-vite-p4kpghhd?file=src%2FFoo.js

function Foo(props) {
  ('react/jsx-runtime');

  return 'meh2';
}

[nojaf]

Thanks for this feedback @hi-ogawa !

[ArnaudBarre]

@nojaf While injecting this works for now, it's mean to be used to add HMR to compiled code, not handwritten code. I highly suggest migrating your files to use .jsx. This gist might be helpful: https://gist.github.com/parties/90cdf35f9a3d05bea6df76dc83a69641

[nojaf]

@ArnaudBarre I'm actually using ReScript which produces compiled JSX.
If my component only returns a primitive string, there is no react/jsx-runtime involved.
That is why I brought it up.