Cannot customize root level admin route

[thgh]

Describe the Bug

Following https://payloadcms.com/docs/beta/admin/overview#customizing-root-level-routes does not allow updating routes.admin

1. It's not allowed by Typescript
2. It cannot find a place to put import map as the admin folder was moved

Link to the code that reproduces this issue

payload/packages/payload/src/bin/generateImportMap/index.ts

Lines 177 to 180 in a8569b9

	if (fs.existsSync(path.resolve(rootDir, 'app/(payload)/admin/'))) {
	importMapFolderPath = path.resolve(rootDir, 'app/(payload)/admin/')
	} else if (fs.existsSync(path.resolve(rootDir, 'src/app/(payload)/admin/'))) {
	importMapFolderPath = path.resolve(rootDir, 'src/app/(payload)/admin/')

Reproduction Steps

1. Move any files from src/app/(payload)/admin one folder up
2. Set routes.admin = '/' in payload config
3. Start dev server

Which area(s) are affected? (Select all that apply)

area: core

Environment Info

Binaries:
Node: 22.5.1
npm: 10.8.2
Yarn: 1.22.22
pnpm: N/A
Relevant Packages:
payload: 3.0.0-beta.117
next: 15.0.1
@payloadcms/db-mongodb: 3.0.0-beta.117
@payloadcms/email-nodemailer: 3.0.0-beta.117
@payloadcms/graphql: 3.0.0-beta.117
@payloadcms/next/utilities: 3.0.0-beta.117
@payloadcms/plugin-cloud: 3.0.0-beta.117
@payloadcms/richtext-lexical: 3.0.0-beta.117
@payloadcms/translations: 3.0.0-beta.117
@payloadcms/ui/shared: 3.0.0-beta.117
react: 19.0.0-rc-65a56d0e-20241020
react-dom: 19.0.0-rc-65a56d0e-20241020

[jeffreylouden]

Is this a duplicate of #7803?

[paulpopus]

1. Setting routes.admin on the top level (note: not inside admin) worked for me just fine on the latest beta TS wise
2. Yeah I can confirm this is an issue and duplicate of ^

Will look into the attached PR, closing this and we'll track progress in that issue

[github-actions]

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