routeTree generation breaks when using different root in vite config

[RMHonor]

Which project does this relate to?

Router

Describe the bug

The previously fixed bug #3624 looks to have regressed.

Your Example Website or App

https://stackblitz.com/edit/github-l4ck9hye?file=vite.config.js

Steps to Reproduce the Bug or Issue

1. Go to the stackblitz link
2. Attempt to run the app
3. Generated folder ./src/generated is created, but is empty

Expected behavior

Generated files are output relative to the Vite root.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.333.32
• OS: macOS
• Browser: Chrome
• Browser Version: 141
• Bundler: Vite
• Bundler Version: 7.1.7

Additional context

I believe the output folder is correctly respecting the Vite root, but the input (i.e. routes folder) does not.

Possibly introduced by https://github.com/TanStack/router/pull/5189/files#diff-f0d23c6a1109a224ba38acbd71932c2aeb3f0e5d855ff06e552f2f7ed7cd1816 ?

[nielsvanvelzen]

Last working version for me is 1.131.50. All my Vite projects use a source folder (src) to avoid mixing actual source code and build scripts. Similar to the reproducible example in this issue.

[nielsvanvelzen]

Issue is not actually fixed with 1.139.6:

> vite
Error: ENOENT: no such file or directory, scandir '/[..]/frontend/app/src/src/routes'
    at /[..]/node_modules/@tanstack/router-generator/dist/cjs/generator.cjs:160:19
    at async generate (/[..]/node_modules/@tanstack/router-plugin/dist/cjs/core/router-generator-plugin.cjs:65:7)
    at async BasicMinimalPluginContext.configResolved (/[..]/node_modules/@tanstack/router-plugin/dist/cjs/core/router-generator-plugin.cjs:83:9)
    at async Promise.all (index 0)
    at async resolveConfig (file:///[..]/node_modules/vite/dist/node/chunks/config.js:36322:2)
    at async _createServer (file:///[..]/node_modules/vite/dist/node/chunks/config.js:26008:67)
    at async CAC.<anonymous> (file:///[..]/node_modules/vite/dist/node/cli.js:572:18)

Using Vite with no options set on the router, just the root folder changed to "src".

export default defineConfig({
	plugins: [
		tanstackRouter(),
		react()
	],

	root: 'src',
});

[nlynzaad]

The original issue was that specified relative paths in the routesDirectory and generatedRouteTree was not resolving correctly against the new root path and this has been addressed. In your case you aren't specifying either and hence the defaults are now being resolved against the new root path.

By default, the root path is the root of the project, and the following is applied:

  routesDirectory: "src/routes"
  generatedRouteTree: "src/routeTree.gen.ts"

The routes directory and generatedRouteTree path can be either absolute paths or relative paths, where the relative paths is always relative to the root.

When you specify the root in the config to src and do not change the routesDirectory or generatedRouteTree then these will resolve to src/src/routes and src/src/routeTree.gen.ts

Either don't specify a root in your config or specify the routesDirectory and generatedRouteTree to be either an absolute path or relative to the new root you specified for example:

  routesDirectory: "./routes"
  generatedRouteTree: "./routeTree.gen.ts"