Function transform

test/cli/samples/log-side-effects/rollup.config.mjs:9–15

(code, id)

		{
			name: 'insert-lines',
			transform(code, id) {
				if (id.endsWith('mapped.js')) {
					const magicString = new MagicString(code);
					magicString.prepend('const removed = true;\nconst alsoRemoved = true; ');
					return { code: magicString.toString(), map: magicString.generateMap({ hires: true }) };
				}
			}
		}
	]
};