fix: handle empty build (#357)

Co-authored-by: Ivan Pantic <[email protected]>
Co-authored-by: Hiroki Osame <[email protected]>

src/plugin.ts

@@ -201,6 +201,12 @@ export default class EsbuildPlugin {
 			 * Webpack 5: https://github.com/webpack/webpack/blob/v5.75.0/lib/SourceMapDevToolModuleOptionsPlugin.js#LL27
 			 */
 			let useSourceMap = false;
+
+			/**
+			 * `finishModules` hook is called after all the `buildModule` hooks are called,
+			 * which is where the `useSourceMap` flag is set
+			 * https://webpack.js.org/api/compilation-hooks/#finishmodules
+			 */
 			compilation.hooks.finishModules.tap(
 				pluginName,
 				(modules) => {
@@ -209,7 +215,9 @@ export default class EsbuildPlugin {
 							? modules[0]
 							: (modules as Set<webpack5.Module>).values().next().value as webpack5.Module
 					);
-					useSourceMap = firstModule.useSourceMap;
+					if (firstModule) {
+						useSourceMap = firstModule.useSourceMap;
+					}
 				},
 			);
 

tests/specs/plugin.ts

@@ -738,5 +738,17 @@ export default testSuite(({ describe }, webpack: typeof webpack4 | typeof webpac
 			expect(exportedFunction('hello world')).toBe('hello world');
 			assertMinified(exportedFunction.toString());
 		});
+
+		// https://github.com/privatenumber/esbuild-loader/issues/356
+		test('can handle empty modules set', async () => {
+			await expect(build(
+				fixtures.blank,
+				(config) => {
+					config.entry = 'not-there.js';
+					configureEsbuildMinifyPlugin(config);
+				},
+				webpack,
+			)).resolves.toBeTruthy();
+		});
 	});
 });