v0.20.15 Regression: Build fails with Cannot read properties of undefined (reading '0') when using ?inline CSS

[TejeshJadhav-cactus]

Describe the bug

After upgrading from 0.20.14 to 0.20.15, the build process fails with a TypeError: Cannot read properties of undefined (reading '0').

The error originates from WXT's internal Vite builder within the assetFileNames hook. It appears the logic introduced in the latest version assumes assetInfo.name is always a string. However, when CSS is imported using the ?inline query (a common pattern for Shadow DOM injection), Vite/Rollup can emit assets where the name is undefined, causing the internal WXT hook to crash.

Reproduction

A minimal setup importing CSS as a string triggers the failure:

src/entrypoints/example.content.ts

import styles from './styles.css?inline';

export default defineContentScript({
  matches: ['*://*/*'],
  main(ctx) {
    console.log("Inlined CSS:", styles);
  },
});

src/entrypoints/styles.css

.test { color: blue; }

Steps to reproduce

1. Use wxt@0.20.15.
2. Import a CSS file with the ?inline suffix in a content script.
3. Run wxt build or wxt dev.
4. The build fails with the following stack trace:

ERROR [vite:css-post] Cannot read properties of undefined (reading '0')

     at assetFileNames (/node_modules/wxt/dist/core/builders/vite/index.mjs:82:56)
     at getCssAssetDirname (/node_modules/vite/dist/node/chunks/dep-C6uTJdX2.js:36210:9)
     at resolveAssetUrlsInCss (/node_modules/vite/dist/node/chunks/dep-C6uTJdX2.js:36329:73)

System Info

System:
    OS: macOS 26.2
    CPU: (10) arm64 Apple M1 Pro
    Memory: 306.31 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.18.0
    npm: 10.9.3
    pnpm: 8.15.7
  Browsers:
    Brave Browser: 142.1.84.132
    Chrome: 144.0.7559.133
    Firefox: 95.0.2
    Safari: 26.2
  npmPackages:
    vite: ^4.4.9 => 4.4.9

Used Package Manager

pnpm

Validations

• 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.
• 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.

[aklinker1]

@PatrykKuniczak you broke something in #2106

[aklinker1]

For now, I'm gonna revert the change. Please fix and open a new PR with the change.

[PatrykKuniczak]

@aklinker1 I'll take a look on that

[aklinker1]

Releasing 0.20.16 now to resolve this issue for now.

[PatrykKuniczak]

@aklinker1 OK, that's looks like, for names ? is also necessary:

 names[0].endsWith('css')

but let's do

 names?[0].endsWith('css')

names can be undefined like name

[aklinker1]

Let's move the discussion over to #2116