rollup-plugin-json/src/index.js

Convert .json files to ES6 modules:

import { createFilter, dataToEsm } from 'rollup-pluginutils';

export default function json(options = {}) {
	const filter = createFilter(options.include, options.exclude);
	const indent = 'indent' in options ? options.indent : '\t';

	return {
		name: 'json',

		transform(json, id) {
			if (id.slice(-5) !== '.json' || !filter(id)) return null;

			return {
				code: dataToEsm(JSON.parse(json), {
					preferConst: options.preferConst,
					compact: options.compact,
					namedExports: options.namedExports,
					indent
				}),
				map: { mappings: '' }
			};
		}
	};
}