fix: handle empty build

src/plugin.ts

@@ -104,13 +104,13 @@
 					? new SourceMapSource(
 						result.code,
 						asset.name,
 						result.map as any,
 						sourceAsString,
 						map as any,
 						true,
 					)
 					: new RawSource(result.code)
 			) as any,
 			{
 				...asset.info,
 				minimized,
@@ -138,7 +138,7 @@
 		this.options = options;
 	}
 
 	apply(compiler: Compiler) {
 		const {
 			implementation,
 			...options
@@ -201,6 +201,12 @@
 			 * 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 @@
 							? 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();
+		});
 	});
 });