error when starting dev server: Cannot read property 'startsWith' of undefined

[Lupeiwen0]

Describe the bug

This error in resolveBuildOptions
const resolve = (p) => p.startsWith('\0') ? p : path__default.resolve(root, p);

Because I have dynamically configured the packaged output file, but this error will be reported when outdir is not configured because the configuration file name is not required in the development environment

Reproduction

Although this may not be a bug, I think it can be optimized because it is not very troublesome

System Info

vite 2.7.1
macOs
chrome lasted

Used Package Manager

yarn

Logs

error when starting dev server:
TypeError: Cannot read property 'startsWith' of undefined
    at resolve (/Users/lupeiwen/Documents/element-compoistion-admin-vite/node_modules/vite/dist/node/chunks/dep-3daf770c.js:43361:30)
    at resolveBuildOptions (/Users/lupeiwen/Documents/element-compoistion-admin-vite/node_modules/vite/dist/node/chunks/dep-3daf770c.js:43362:23)
    at resolveConfig (/Users/lupeiwen/Documents/element-compoistion-admin-vite/node_modules/vite/dist/node/chunks/dep-3daf770c.js:81935:34)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async createServer (/Users/lupeiwen/Documents/element-compoistion-admin-vite/node_modules/vite/dist/node/chunks/dep-3daf770c.js:67541:20)
    at async CAC.<anonymous> (/Users/lupeiwen/Documents/element-compoistion-admin-vite/node_modules/vite/dist/node/cli.js:688:24)

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 https://github.com/vuejs/vue-next instead.
• 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.

[ydcjeff]

Seems caused by #5601

Can you provide a reproduction?

Thanks!

[github-actions]

Hello @Lupeiwen0. 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.