From 7b948efbf191ce0b35b92b934b528545dfaefe18 Mon Sep 17 00:00:00 2001
From: Philip Cox <neogeneva@gmail.com>
Date: Fri, 8 Mar 2024 17:50:07 +1300
Subject: [PATCH] feat: enable `dynamic-imports` by default (#361)

Co-authored-by: Hiroki Osame <hiroki.osame@gmail.com>
---
 src/loader.ts         |  8 +++++++
 tests/specs/loader.ts | 51 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/src/loader.ts b/src/loader.ts
index 38fd3c1..c8453b3 100644
--- a/src/loader.ts
+++ b/src/loader.ts
@@ -90,6 +90,14 @@ async function ESBuildLoader(
 		}
 	}
 
+	/**
+	 * Enable dynamic import by default to support code splitting in Webpack
+	 */
+	transformOptions.supported = {
+		'dynamic-import': true,
+		...transformOptions.supported,
+	};
+
 	try {
 		const { code, map } = await transform(source, transformOptions);
 		done(null, code, map && JSON.parse(map));
diff --git a/tests/specs/loader.ts b/tests/specs/loader.ts
index 6807fd6..3329fcb 100644
--- a/tests/specs/loader.ts
+++ b/tests/specs/loader.ts
@@ -407,5 +407,56 @@ export default testSuite(({ describe }, webpack: typeof webpack4 | typeof webpac
 			const code = built.fs.readFileSync('/dist/index.js', 'utf8');
 			expect(code).toContain('div{color:red}');
 		});
+
+		test('Keeps dynamic imports by default', async () => {
+			const built = await build(
+				{
+					'/src/index.js': 'export default async () => (await import("./test2.js")).default',
+					'/src/test2.js': 'export default "test2"',
+				},
+				(config) => {
+					configureEsbuildLoader(config, { options: { target: 'chrome52' } });
+				},
+				webpack,
+			);
+
+			expect(built.stats.hasWarnings()).toBe(false);
+			expect(built.stats.hasErrors()).toBe(false);
+
+			const { assets } = built.stats.compilation;
+			expect(assets).toHaveProperty(['index.js']);
+
+			// Chunk split because esbuild preserved the dynamic import
+			expect(Object.keys(assets).length).toBe(2);
+			expect(await built.require('/dist')()).toBe('test2');
+		});
+
+		test('Dynamic imports can be disabled', async () => {
+			const built = await build(
+				{
+					'/src/index.js': 'export default async () => (await import("./test2.js")).default',
+					'/src/test2.js': 'export default "test2"',
+				},
+				(config) => {
+					configureEsbuildLoader(config, {
+						options: {
+							target: 'chrome52',
+							supported: { 'dynamic-import': false },
+						},
+					});
+				},
+				webpack,
+			);
+
+			expect(built.stats.hasWarnings()).toBe(false);
+			expect(built.stats.hasErrors()).toBe(false);
+
+			const { assets } = built.stats.compilation;
+			expect(assets).toHaveProperty(['index.js']);
+
+			// No chunk split because esbuild removed the dynamic import
+			expect(Object.keys(assets).length).toBe(1);
+			expect(await built.require('/dist')()).toBe('test2');
+		});
 	});
 });