@drewigg/agadoo/index.js

Check whether a package is tree-shakeable

const path = require('path');
const { rollup } = require('rollup');
const acorn = require('acorn');
const virtual = require('@rollup/plugin-virtual');

exports.check = input => {
	const resolved = path.resolve(input);

	return rollup({
		input: '__agadoo__',
		plugins: [
			virtual({
				__agadoo__: `import ${JSON.stringify(resolved)}`
			})
		],
		onwarn: (warning, handle) => {
			if (warning.code !== 'EMPTY_BUNDLE') handle(warning);
		}
	}).then(bundle => bundle.generate({
		format: 'esm'
	})).then(result => {
		const { code } = result.output[0];

		const ast = acorn.parse(code, {
			ecmaVersion: 11,
			sourceType: 'module'
		});

		const nodes = ast.body.filter(node => {
			return node.type !== 'ImportDeclaration';
		});

		console.log(code);

		return {
			shaken: nodes.length === 0
		};
	});
};