fix: prevent empty JS file generation for CSS-only entry points

DukeDeSouth · cursoragent · DukeDeSouth · commit fbfa382c87cf · 2026-02-07T16:24:14.000-05:00
When CSS files are used as entry points (e.g., `entry: { styles: './styles.css' }`), webpack generates an unnecessary empty .js file alongside the CSS output. Root cause: `chunkHasJs()` returns true for any chunk with entry modules without checking their source types, and `chunkHasRuntimeOrJs()` returns true whenever runtime modules exist, even when there are no JavaScript entry modules that need bootstrapping. Fix: - `chunkHasJs()`: Check entry module source types instead of blindly returning true for any entry module. Only return true when at least one entry module has JavaScript source type. - `chunkHasRuntimeOrJs()`: When runtime modules exist but there are entry modules in the chunk, verify that at least one entry module has JavaScript source type before emitting JS. For standalone runtime chunks (optimization.runtimeChunk: true), keep JS emission since the runtime bootstrap is needed for other entry chunks. Fixes #11671 Co-authored-by: Cursor <cursoragent@cursor.com>
diff --git a/lib/javascript/JavascriptModulesPlugin.js b/lib/javascript/JavascriptModulesPlugin.js
@@ -81,7 +81,13 @@ const JavascriptParser = require("./JavascriptParser");
  * @returns {boolean} true, when a JS file is needed for this chunk
  */
 const chunkHasJs = (chunk, chunkGraph) => {
-	if (chunkGraph.getNumberOfEntryModules(chunk) > 0) return true;
+	if (chunkGraph.getNumberOfEntryModules(chunk) > 0) {
+		for (const module of chunkGraph.getChunkEntryModulesIterable(chunk)) {
+			if (chunkGraph.getModuleSourceTypes(module).has(JAVASCRIPT_TYPE)) {
+				return true;
+			}
+		}
+	}
 
 	return Boolean(
 		chunkGraph.getChunkModulesIterableBySourceType(chunk, JAVASCRIPT_TYPE)
@@ -94,18 +100,32 @@ const chunkHasJs = (chunk, chunkGraph) => {
  * @returns {boolean} true, when a JS file is needed for this chunk
  */
 const chunkHasRuntimeOrJs = (chunk, chunkGraph) => {
+	if (chunkGraph.getChunkModulesIterableBySourceType(chunk, JAVASCRIPT_TYPE)) {
+		return true;
+	}
+
 	if (
 		chunkGraph.getChunkModulesIterableBySourceType(
 			chunk,
 			WEBPACK_MODULE_TYPE_RUNTIME
 		)
 	) {
-		return true;
+		const numEntryModules = chunkGraph.getNumberOfEntryModules(chunk);
+		if (numEntryModules === 0) {
+			// Runtime-only chunk (e.g. optimization.runtimeChunk: true) —
+			// keep JS for bootstrap code that loads other entry chunks
+			return true;
+		}
+		// Entry modules exist in this chunk — only emit JS if any need JavaScript
+		for (const module of chunkGraph.getChunkEntryModulesIterable(chunk)) {
+			if (chunkGraph.getModuleSourceTypes(module).has(JAVASCRIPT_TYPE)) {
+				return true;
+			}
+		}
+		return false;
 	}
 
-	return Boolean(
-		chunkGraph.getChunkModulesIterableBySourceType(chunk, JAVASCRIPT_TYPE)
-	);
+	return false;
 };
 
 /**
diff --git a/test/configCases/asset-modules/only-entry/test.js b/test/configCases/asset-modules/only-entry/test.js
@@ -26,12 +26,13 @@ it("should work", () => {
 			break;
 		}
 		case 2: {
-			expect(stats.assets.length).toBe(4);
+			// CSS-only entry should NOT generate an empty .js file (#11671)
+			expect(stats.assets.length).toBe(3);
 
 			const cssEntryInJs = stats.assets.find(
 				a => a.name.endsWith("css-entry.js")
 			);
-			expect(Boolean(cssEntryInJs)).toBe(true);
+			expect(Boolean(cssEntryInJs)).toBe(false);
 
 			const cssEntry = stats.assets.find(
 				a => a.name.endsWith("css-entry.css")
@@ -40,7 +41,8 @@ it("should work", () => {
 			break;
 		}
 		case 3: {
-			expect(stats.assets.length).toBe(5);
+			// JS entry keeps .js, CSS-only entry should NOT generate .js (#11671)
+			expect(stats.assets.length).toBe(4);
 
 			const jsEntry = stats.assets.find(
 				a => a.name.endsWith("js-entry.js")
@@ -50,7 +52,7 @@ it("should work", () => {
 			const cssEntryInJs = stats.assets.find(
 				a => a.name.endsWith("css-entry.js")
 			);
-			expect(Boolean(cssEntryInJs)).toBe(true);
+			expect(Boolean(cssEntryInJs)).toBe(false);
 
 			const cssEntry = stats.assets.find(
 				a => a.name.endsWith("css-entry.css")
@@ -59,6 +61,7 @@ it("should work", () => {
 			break;
 		}
 		case 4: {
+			// Node target: CSS entry generates JS (exports class names, no CSS output)
 			expect(stats.assets.length).toBe(4);
 
 			const jsEntry = stats.assets.find(
