Rollup config: Extracted CSS sourcemaps always generated

[laurentpayot]

config.client.output() always return an object with a truthy sourcemap property, so I get sourcemap files for both js and css files.

Even when using

output: {...config.client.output(), sourcemap: dev}

when dev is falsy I still get sourcemap files for css files (but not for js files).

Is it related to #421 ?

[teoxoy]

This happens because rollup doesn't care about other sourcemaps than js ones.

The only way to get this to work is to pass in a sourcemap option to rollup-plugin-svelte. This not currently supported but I am looking into it and will probably start a PR for it.

[teoxoy]

Looks like sapper does some custom plugin injection for rollup and the answer was to implement this into sapper. I included a commit that will add this functionality in my PR.