Deprecation warning

My config:

postcss( {
        modules: false,  
        extract: true,  
        extensions: [ ".css" ],  
        minimize: true,  
        sourceMap: true  
      })

This emits deprecation warning from rollup:

(!) A plugin is directly adding properties to the bundle object in the “generateBundle” hook. This is deprecated and will be removed in a future Rollup version, please use “this.emitFile” instead.

[SASUKE40]

Please use #197 solution or other fix, this warning in watch mode looks extremely bad, it is printed on every rebuild:

🙏

The rollup v2 adaptation is still work in progress and will be released soon to resolve this warning.

[MrJohz]

Aha, thanks! To fix that, would some sort of migration path make sense? E.g:

extract: true -> use this.emitFile and avoid the deprecation warning extract:'string' -> use the existing bundle[filename] assignment.

Alternatively, a new configuration key could be given: emit (which is just a boolean value). It would be an error to configure both emit and extract at the same time.

I think adding the new configuration key is the only way to avoid any breaking changes, but it also adds more configuration options, which is also difficult. I’m happy to put together a pull request for any of these options - which do you think makes the most sense?