bug(ssr): vite hmr server called twice when use two configurations in server side render

[zhangyuang]

Describe the bug

In vite ssr, if I separate vite config logic to different files like vite.client.config.ts and vite.server.config.ts, and I get viteDevServer instance by calling createServer method use these configurations.

On the server side, I use ssrLoadModule in the viteDevServer instance, like

const viteServer = await createServer(serverConfig)
await (viteServer as ViteDevServer).ssrLoadModule(viteServerEntry)

On the client side, I use a ViteDevServer instance with middleware mode, like

const viteServer: ViteDevServer = await createServer(clientConfig)
proxyMiddlewaresArr.push(viteServer.middlewares)

It's a common practice in server-side render projects. But in rolldown-vite, the websocket server will call the listen function twice because createServer is called twice. In my opinion, there is no need to create a Websocket server when I only use ViteDevServer for ssrLoadModule.

I can confirm the logic is expected in vite@^2.0.0 because I am upgrading vite@2.0.0 to rolldown-vite in my server-side render framework.

Reproduction

reproduce

Steps to reproduce

$ git clone git@github.com:zhangyuang/vite-ssr-external-bug.git
$ git checkout bug/ssrdevserver
$ yarn && npm run dev

System Info

System:
    OS: macOS 15.5
    CPU: (14) arm64 Apple M4 Pro
    Memory: 1012.33 MB / 48.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.4.1 - ~/Library/pnpm/node
    Yarn: 1.22.22 - ~/Library/pnpm/yarn
    npm: 10.8.2 - ~/Library/pnpm/npm
    pnpm: 10.13.1 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 138.0.7204.169
    Firefox Nightly: 140.0a1
    Safari: 18.5
  npmPackages:
    vite: ^7.0.0 => 7.0.6

Used Package Manager

npm

Logs

No response

Validations

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• Read the Contributing Guidelines.
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• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[zhangyuang]

I found that in vite2.0, the logic here is like this

 wss.on('error', (e) => {
        if (e.code !== 'EADDRINUSE') {
            config.logger.error(colors$1.red(`WebSocket server error:\n${e.stack || e.message}`), { error: e });
        }
    });

There is no display EADDRINUSE error info🤔

[github-actions]

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

[zhangyuang]

Add minimal reproduction https://github.com/zhangyuang/vite-ssr-external-bug/tree/bug/ssrdevserver

How to reproduce

$ git clone git@github.com:zhangyuang/vite-ssr-external-bug.git
$ git checkout bug/ssrdevserver
$ yarn && npm run dev

In this repo, I separate Vite config into two parts: client and server. This may seem unnecessary in this demo. But in a complex SSR project or framework, there are several differences between server-side configuration and client-side. So we need to separate them.