Invisible name clash when importing a css file in same-named JS file

[WoodyWoodsta]

Reproduction link or steps

https://stackblitz.com/edit/github-mcmfinbh?file=tsdown.config.mts

What is expected?

Can import a css file which is the same name as a js file.

What is actually happening?

When importing a css file which has the same name as the JS file, the output incudes he JS file name with 2 appended, and the output includes a require to the original file name (which does not exist).

Any additional comments?

I'm not sure if commonjs is to blame, or something else.

[WoodyWoodsta]

In fact, I think there is something more to this as well, which is that when you import a css file, it for some reason is output as a require('css-filename.js'), when instead it should be preserving the require as a css file for consuming bundlers to pick up and manage.

When switching to esm output, and making sure that css.inject = true, the correct import is included in the output - so it seems to be isolated to commonjs.

[WoodyWoodsta]

One more finding: when css.inject = false and format = 'commonjs', the require(css-filename.js) is still present in the output.