`SidebarItem.base` overrides parent `SidebarMulti.base` instead of inheriting

[Ackerven]

Is your feature request related to a problem? Please describe.

Sidebar define in code:

export type Sidebar = SidebarItem[] | SidebarMulti;

export interface SidebarMulti {
  [path: string]: SidebarItem[] | { items: SidebarItem[]; base: string };
}

export type SidebarItem = {
  text?: string;
  link?: string;
  items?: SidebarItem[];
  collapsed?: boolean;
  base?: string;
  docFooterText?: string;
  rel?: string;
  target?: string;
};

This is a direcotry structure:

└── misc
    ├── cap1.md
    ├── cap2
    │   ├── cap2-1.md
    │   └── index.md
    ├── index.md
    └── intro.md

I config sidebar in config.mts:

sidebar: {
  '/misc': {
    base: '/misc',
    items: [
      { text: 'Intro', link: '/intro' },
      { text: 'Cap1', link: '/cap1' },
      {
        text: 'Cap2',
        base: '/cap2',
        items: [{ text: 'Cap2.1', link: '/cap2-1' }],
      },
    ],
  },
}

Actual routes:

/misc/intro.html
/misc/cap1.html
/cap2/cap2-1.html

Describe the solution you'd like

In this setup, it looks like SidebarItem.base completely replaces the SidebarMulti.base, instead of working relative to it — which feels a bit unexpected.

Would it be possible for VitePress to support making nested base values inherit from the parent?

Something like this:

/misc/intro.html
/misc/cap1.html
/misc/cap2/cap2-1.html

That’d make things way more intuitive, especially when building out deeper folder structures.

Describe alternatives you've considered

No response

Additional context

Vitepress version: 2.0.0-alpha.7

Here is a minimal reproduction: https://stackblitz.com/edit/vite-yrm66kkm?file=docs%2F.vitepress%2Fconfig.ts

Validations

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