feat: support dynamic imports

package.json

@@ -49,6 +49,7 @@
 	"dependencies": {
 		"@rollup/plugin-alias": "^5.1.1",
 		"@rollup/plugin-commonjs": "^28.0.2",
+		"@rollup/plugin-dynamic-import-vars": "^2.1.5",
 		"@rollup/plugin-inject": "^5.0.5",
 		"@rollup/plugin-json": "^6.1.0",
 		"@rollup/plugin-node-resolve": "^16.0.0",

src/utils/get-rollup-configs.ts

@@ -7,6 +7,7 @@ import commonjs from '@rollup/plugin-commonjs';
 import json from '@rollup/plugin-json';
 import alias from '@rollup/plugin-alias';
 import replace from '@rollup/plugin-replace';
+import dynamicImportVars from '@rollup/plugin-dynamic-import-vars';
 import type { PackageJson } from 'type-fest';
 import type { TsConfigResult } from 'get-tsconfig';
 import type { ExportEntry, AliasMap } from '../types.js';
@@ -137,6 +138,7 @@ const getConfig = {
 				json(),
 				esbuildTransform(esbuildConfig),
 				createRequire(),
+				dynamicImportVars(),
 				...(
 					options.minify
 						? [esbuildMinify(esbuildConfig)]

tests/fixtures.ts

@@ -234,3 +234,26 @@ export const fixtureDependencyImportsMap: FileTree = {
 		}),
 	},
 };
+
+export const fixtureDynamicImports: FileTree = {
+	'package.json': createPackageJson({
+		main: './dist/dynamic-imports.js',
+	}),
+	src: {
+		'dynamic-imports.js': outdent`
+		const files = [
+			'aaa',
+			'bbb',
+			'ccc',
+		];
+		const randomFile = files[Math.floor(Math.random() * files.length)];
+		import(\`./files/\${randomFile}.js\`)
+		`,
+
+		files: {
+			'aaa.js': 'console.log(111)',
+			'bbb.js': 'console.log(222)',
+			'ccc.js': 'console.log(333)',
+		},
+	},
+};

tests/specs/builds/output-commonjs.ts

@@ -1,7 +1,10 @@
+import fs from 'node:fs/promises';
 import { testSuite, expect } from 'manten';
 import { createFixture } from 'fs-fixture';
 import { pkgroll } from '../../utils.js';
-import { packageFixture, createPackageJson, createTsconfigJson } from '../../fixtures.js';
+import {
+	packageFixture, createPackageJson, createTsconfigJson, fixtureDynamicImports,
+} from '../../fixtures.js';
 
 export default testSuite(({ describe }, nodePath: string) => {
 	describe('output: commonjs', ({ test }) => {
@@ -175,5 +178,31 @@ export default testSuite(({ describe }, nodePath: string) => {
 			const content = await fixture.readFile('dist/nested/index.js', 'utf8');
 			expect(content).toMatch('nested entry point');
 		});
+
+		test('dynamic imports', async () => {
+			await using fixture = await createFixture({
+				...fixtureDynamicImports,
+				'package.json': createPackageJson({
+					exports: './dist/dynamic-imports.cjs',
+				}),
+			});
+
+			const pkgrollProcess = await pkgroll([], {
+				cwd: fixture.path,
+				nodePath,
+			});
+
+			expect(pkgrollProcess.exitCode).toBe(0);
+			expect(pkgrollProcess.stderr).toBe('');
+
+			const content = await fixture.readFile('dist/dynamic-imports.cjs', 'utf8');
+			expect(content).toMatch('require(');
+
+			const files = await fs.readdir(fixture.getPath('dist'));
+			files.sort();
+			expect(files[0]).toMatch(/^aaa-/);
+			expect(files[1]).toMatch(/^bbb-/);
+			expect(files[2]).toMatch(/^ccc-/);
+		});
 	});
 });

tests/specs/builds/output-module.ts

@@ -1,7 +1,10 @@
+import fs from 'node:fs/promises';
 import { testSuite, expect } from 'manten';
 import { createFixture } from 'fs-fixture';
 import { pkgroll } from '../../utils.js';
-import { packageFixture, createPackageJson, createTsconfigJson } from '../../fixtures.js';
+import {
+	packageFixture, createPackageJson, createTsconfigJson, fixtureDynamicImports,
+} from '../../fixtures.js';
 
 export default testSuite(({ describe }, nodePath: string) => {
 	describe('output: module', ({ test }) => {
@@ -243,5 +246,31 @@ export default testSuite(({ describe }, nodePath: string) => {
 			const [, createRequireMangledVariable] = content.toString().match(/createRequire as (\w+)/)!;
 			expect(content).not.toMatch(`${createRequireMangledVariable}(`);
 		});
+
+		test('dynamic imports', async () => {
+			await using fixture = await createFixture({
+				...fixtureDynamicImports,
+				'package.json': createPackageJson({
+					exports: './dist/dynamic-imports.mjs',
+				}),
+			});
+
+			const pkgrollProcess = await pkgroll([], {
+				cwd: fixture.path,
+				nodePath,
+			});
+
+			expect(pkgrollProcess.exitCode).toBe(0);
+			expect(pkgrollProcess.stderr).toBe('');
+
+			const content = await fixture.readFile('dist/dynamic-imports.mjs', 'utf8');
+			expect(content).toMatch('import(');
+
+			const files = await fs.readdir(fixture.getPath('dist'));
+			files.sort();
+			expect(files[0]).toMatch(/^aaa-/);
+			expect(files[1]).toMatch(/^bbb-/);
+			expect(files[2]).toMatch(/^ccc-/);
+		});
 	});
 });