fix: mark asset module as side-effect-free when futureDefaults (#20535)

hai-x · web-flow · commit 4f5c0a864d06 · 2026-02-25T17:06:49.000+03:00
diff --git a/.changeset/eighty-vans-tie.md b/.changeset/eighty-vans-tie.md
@@ -0,0 +1,5 @@
+---
+"webpack": patch
+---
+
+Only mark asset modules as side-effect-free when `experimental.futureDefaults` is set to true, so asset-copying use cases (e.g. `import "./x.png"`) won’t break unless the option is enabled.
diff --git a/lib/WebpackOptionsApply.js b/lib/WebpackOptionsApply.js
@@ -372,7 +372,9 @@ class WebpackOptionsApply extends OptionsApply {
 
 		new JavascriptModulesPlugin().apply(compiler);
 		new JsonModulesPlugin().apply(compiler);
-		new AssetModulesPlugin().apply(compiler);
+		new AssetModulesPlugin({
+			sideEffectFree: options.experiments.futureDefaults
+		}).apply(compiler);
 
 		if (!options.experiments.outputModule) {
 			if (options.output.module) {
diff --git a/lib/asset/AssetModulesPlugin.js b/lib/asset/AssetModulesPlugin.js
@@ -86,7 +86,19 @@ const getNormalModule = memoize(() => require("../NormalModule"));
 const type = ASSET_MODULE_TYPE;
 const PLUGIN_NAME = "AssetModulesPlugin";
 
+/**
+ * @typedef {object} AssetModulesPluginOptions
+ * @property {boolean=} sideEffectFree
+ */
+
 class AssetModulesPlugin {
+	/**
+	 * @param {AssetModulesPluginOptions} options options
+	 */
+	constructor(options) {
+		this.options = options;
+	}
+
 	/**
 	 * Apply the plugin
 	 * @param {Compiler} compiler the compiler instance
@@ -112,7 +124,10 @@ class AssetModulesPlugin {
 								/** @type {NormalModuleCreateData} */
 								(createData)
 							);
-							module.factoryMeta = { sideEffectFree: true };
+							if (this.options.sideEffectFree) {
+								module.factoryMeta = { sideEffectFree: true };
+							}
+
 							return module;
 						});
 				}
diff --git a/test/__snapshots__/StatsTestCases.basictest.js.snap b/test/__snapshots__/StatsTestCases.basictest.js.snap
@@ -136,8 +136,7 @@ chunk {main} (runtime: main) bundle.js (main) X bytes (javascript) X bytes (runt
   data:text/plain;base64,szsaAAdsadasdfaf.. X bytes {main} [depth 1] [dependent] [built] [code generated]
     [no exports]
     [used exports unknown]
-    [inactive] harmony side effect evaluation data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 1:0-82
-    harmony import specifier data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 4:8-13
+    harmony side effect evaluation data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 1:0-82
   webpack/runtime/make namespace object X bytes {main} [code generated]
     [no exports]
     [used exports unknown]
@@ -148,8 +147,7 @@ chunk {main} (runtime: main) bundle.js (main) X bytes (javascript) X bytes (runt
 data:text/plain;base64,szsaAAdsadasdfaf.. X bytes {main} [depth 1] [built] [code generated]
   [no exports]
   [used exports unknown]
-  [inactive] harmony side effect evaluation data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 1:0-82
-  harmony import specifier data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 4:8-13
+  harmony side effect evaluation data:text/plain;base64,szsaAAdsadasdfaf.. [./index.js] 1:0-82
 webpack/runtime/make namespace object X bytes {main} [code generated]
   [no exports]
   [used exports unknown]
diff --git a/test/configCases/side-effects/asset-module/webpack.config.js b/test/configCases/side-effects/asset-module/webpack.config.js
@@ -36,5 +36,8 @@ module.exports = {
 		sideEffects: true,
 		moduleIds: "named",
 		concatenateModules: false
+	},
+	experiments: {
+		futureDefaults: true
 	}
 };
diff --git a/test/fixtures/uses-asset.js b/test/fixtures/uses-asset.js
@@ -1,5 +1 @@
 import SVG from "./file.svg";
-
-const call = () => SVG;
-
-call();
diff --git a/test/statsCases/all-stats/index.js b/test/statsCases/all-stats/index.js
@@ -1,7 +1 @@
 import text1 from "data:text/plain;base64,szsaAAdsadasdfafasfasAADas123aasdasd==";
-
-const call = () => {
-	return text1;
-};
-
-call();
diff --git a/test/statsCases/asset-concat/index.js b/test/statsCases/asset-concat/index.js
@@ -7,8 +7,3 @@ import text2 from "data:text/plain,asd=";
 import text3 from "data:text/plain,XXXXXXXXXXXXXXXXX"; // 17 chars
 import css from "./a.css";
 import source from "./a.source";
-
-const call = () =>
-	png + svg + jpg + html + text1 + text2 + text3 + css + source;
-
-call();
diff --git a/test/statsCases/asset/index.js b/test/statsCases/asset/index.js
@@ -7,8 +7,3 @@ import text2 from "data:text/plain,asd=";
 import text3 from "data:text/plain,XXXXXXXXXXXXXXXXX"; // 17 chars
 import css from "./a.css";
 import source from "./a.source";
-
-const call = () =>
-	png + svg + jpg + html + text1 + text2 + text3 + css + source;
-
-call();

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +"webpack": patch
 +---
++
 +Only mark asset modules as side-effect-free when `experimental.futureDefaults` is set to true, so asset-copying use cases (e.g. `import "./x.png"`) won’t break unless the option is enabled.
Original file line number	Diff line number	Diff line change
`@@ -36,5 +36,8 @@ module.exports = {`
`36`	`36`	`sideEffects: true,`
`37`	`37`	`moduleIds: "named",`
`38`	`38`	`concatenateModules: false`
	`39`	`+ },`
	`40`	`+ experiments: {`
	`41`	`+ futureDefaults: true`
`39`	`42`	`}`
`40`	`43`	`};`