Vite is seemingly creating empty/junk source maps when optimizing dependencies

[rschristian]

Describe the bug

When running a very basic Preact app (see reproduction), in FireFox (perhaps elsewhere too, unsure), users see warnings of No sources are declared in this source map and indeed, the optimized dependencies have empty generated source maps.

Warning & Source Map

Source map error: No sources are declared in this source map.
Resource URL: http://localhost:3000/node_modules/.vite/deps/preact.js?v=2552327c
Source Map URL: preact.js.map

Repeat this warning then for every dependency

node_modules/.vite/deps/preact.js.map

{
  "version": 3,
  "sources": [],
  "sourcesContent": [],
  "mappings": "",
  "names": []
}

I see nothing at this time that indicates an issue with Preact's source maps (and in fact, I see this same issue for modules that have no build step and, ergo, no source maps) though even if there was (and I'll keep looking), generating empty source maps like this creates a lot of noise with no value; I'd prefer if no source map was created at all at that point. Seeing 15 warnings of empty source maps is not very helpful.

Potentially related to #7767

Reproduction

https://stackblitz.com/edit/vitejs-vite-xbgtoq?file=src%2Fmain.jsx

Steps to reproduce

1. Run npm install && npm run dev
2. Run open node_modules/.vite/deps/preact.js.map
3. See empty source map

System Info

System:
    OS: Linux 6.9 EndeavourOS
    CPU: (4) x64 AMD Ryzen 7 5800X 8-Core Processor
    Memory: 3.44 GB / 11.65 GB
    Container: Yes
    Shell: 5.9 - /usr/bin/zsh
  Binaries:
    Node: 22.2.0 - /usr/bin/node
    Yarn: 1.22.22 - /usr/bin/yarn
    npm: 10.8.1 - /usr/bin/npm
    pnpm: 9.3.0 - /usr/bin/pnpm
  Browsers:
    Chromium: 125.0.6422.141
  npmPackages:
    vite: ^5.2.2 => 5.3.0

Used Package Manager

npm

Logs

No response

Validations

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• 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 vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[stackblitz]

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• vitejs-vite-xbgtoq (Open reproduction)