Avoid importing `.css` files in the published files

[abdonrd]

Describe the bug

https://unpkg.com/browse/@material/mwc-button@0.22.1/mwc-button.js

I just checking the @material/mwc-button and it has this CSS import line:

import { styles } from './styles.css';

But the browser can't load this .css file (at least without server magic).

Expected behavior

Use code that the browser understand.

Maybe as .css.js?

import { styles } from './styles.css.js';

[dfreedm]

I think for both this reason, and future support of Import Maps, we'll have to evaluate adding .js file extensions to our built files.

Our internal styleguide for Typescript precludes adding using file extensions on source files, so we'll probably look first at using some tooling in the build process to add file extensions.

[thescientist13]

Our internal styleguide for Typescript precludes adding using file extensions on source files, so we'll probably look first at using some tooling in the build process to add file extensions.

This would be great to see! Started testing out MWC myself and also ran into this.

Also and apologies if I am missing it, but I don't actually see that styles.css in the published package. Is that expected? 🔍 👀

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On a related note, would this effort also address the missing .js extension as well from files also referenced in the entry point? Like mwc-button-base? I'm think that per the spec that files need to have an extension, so would / could this be part of a related effort to address extensions within the project?

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Not sure if any of these points are worth raising on the README but happy to submit a PR to help highlight any of these considerations and / or making an issue to track.

Thanks! ✌️

[thescientist13]

Ah, after thinking about it some more, it seems that the assumption is that @material/mwc-button/styles.css will be resolved to @material/mwc-button/styles.css.js presumably by checking / adding the .js at the consumer level? Sorry if I missed all this in the docs. 😞

Should be easy enough to work around but I think per spec compliance, and to favor being explicit over implicit, it would be great if MWC could always set the extension of the file being imported. 🙏

[dfreedm]

Merging this issue into #2632