Describe the bug

Multi-page apps created with Vite do not behave consistently between dev and build preview when visiting nested URLs that do not have a trailing slash.

Using the following folder structure:

├── package.json
├── vite.config.js
├── index.html
└── nested
    └── index.html

Expected: Both dev and build servers have consistent behavior when visiting <root>/nested

Actual: Dev server shows index.html from root when visiting <root>/nested; must use <root>/nested/ instead. Build preview, however, shows nested/index.html when visiting <root>/nested.

Reproduction

https://github.com/noahmpauls/vite-bug-multipage-url

System Info

System:
    OS: Windows 10 10.0.19043
    CPU: (8) x64 Intel(R) Core(TM) i7-8565U CPU @ 1.80GHz
    Memory: 1.02 GB / 7.75 GB
  Binaries:
    Node: 14.15.5 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.5 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 6.14.11 - C:\Program Files\nodejs\npm.CMD
  npmPackages:
    vite: ^2.7.2 => 2.7.13

Used Package Manager

npm

Logs

No response

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.