The rollup plugin cannot resolve component namespace and name properly on Windows

[Mr-VincentW]

Description

Here's a snippet grabbed from /packages/@lwc/rollup-plugin/src/index.ts:332

const [namespace, name] =
// Note we do not need to use path.sep here because this filename contains
// a '/' regardless of Windows vs Unix, since it comes from the Rollup `id`
specifier?.split('/') ??  #path.dirname(filename).split('/').slice(-2);

As per the comments, specifiers should only contain / as path delimiters. However, in my case (on Windows), I found them cometimes containing \ as well. Using /[\\/]/ here solves the problem for me.

BTW, extracting namespace and name from path.dirname(filename) also not working for relative filename like ./filename.css.

Steps to Reproduce

• Set up an LWC Rollup develop env (https://lwc.dev/guide/install#via-rollup)
• Create a custom component
• Run it

Expected Results

No warning messages in the console regarding this reason.

Actual Results

Tons of these messages as each component may prompt one for js, html, and css each.

Version

"@lwc/rollup-plugin": "^8.12.2",
"lwc": "^8.12.2",
"rollup": "^4.29.1"

Possible Solution

Replace .split('/') with .split(/[\\/]/)

[cardoso]

@Mr-VincentW could you submit a PR with your solution so it can be tested in CI?

BTW, extracting namespace and name from path.dirname(filename) also not working for relative filename like ./filename.css.

If I'm not mistaken at the point where path.dirname is used the filename is already resolved to an absolute path.

[Mr-VincentW]

PR created.

If I'm not mistaken at the point where path.dirname is used the filename is already resolved to an absolute path.

Not for CSS files referenced by HTML templates. However, I don't think it really impacts the subsequent processes for them.

[cardoso]

In theory this could be a bug in rollup itself, but looking at the changelogs for 4.29.1 (your version), 4.29.2, 4.30.0, 4.30.1 (latest), there's no clear indication that upgrading your version would fix it.

But just in case, are you able to upgrade to latest and confirm the issue still happens?