rollup/test/form/custom-module-context-function/_config.js

module.exports = {
	description: 'allows custom module-specific context with a function option',
	options: {
		moduleContext ( id ) {
			return /main\.js$/.test( id ) ? 'lolwut' : 'undefined';
		},
		onwarn ( warning ) {
			if ( warning.code !== 'THIS_IS_UNDEFINED' ) throw new Error( 'unexpected warning' );
		}
	}
};