Bug: No source locations in errors when using `bundleAsync()`

[JoshuaWise]

Hi, I want to use bundleAsync with a custom resolver, but I want to display nice error messages if either resolver.read or resolver.resolve throw an error (or return a rejected Promise). But I don't currently see any way to get the source location of the @import rule being processed. Even if I just let the error bubble up, lightningcss just throws Error: GenericFailure, Promise rejected with no other information. Is there something I'm missing?

[JoshuaWise]

I just realized, even if there's a syntax error in the CSS, the errors thrown by lightningcss just don't have any source location info. That makes this library kind of unusable for my purposes, which is too bad because I got really excited about replacing PostCSS. What are the chances source locations can be added to errors?

[devongovett]

It's there. See the loc and fileName properties of the error object.

lightningcss/node/src/lib.rs

Line 1010 in 11f4179

obj.set_named_property("loc", loc)?;

[JoshuaWise]

It doesn't appear to be working as intended. I can reproduce the issue with this simple script:

'use strict';
const { bundleAsync } = require('lightningcss');

(async function main() {
	try {
		await bundleAsync({
			filename: 'style.css',
			minify: true,
			sourceMap: true,
		});
		console.log('No error!');
	} catch (err) {
		console.log(`Error: ${err.message}`);
		console.log(`Properties: ${Object.getOwnPropertyNames(err).join(', ')}`);
		console.log(`fileName: ${err.filename}`);
		console.log(`loc: ${err.loc}`);
	}
})();

With this style.css file:

.foo {
	-webkit-flex 1; /* this line has a syntax error */
	flex: 1;
}

I get the following logs:

Error: Unexpected token Number { has_sign: false, value: 1.0, int_value: Some(1) }
Properties: stack, message, code
fileName: undefined
loc: undefined

[JoshuaWise]

FWIW, I'm using Node.js v18.13.0, and lightningcss v1.21.0

[devongovett]

Hmm bundleAsync may be an exception. I'll have to look into it

[JoshuaWise]

Thanks, I shall be awaiting what you find 😊