alexander-akait · Sep 2, 2026 · Sep 1, 2026 · Sep 1, 2026 · Sep 1, 2026
diff --git a/.changeset/012-anonymous-default-class-name.md b/.changeset/012-anonymous-default-class-name.md
@@ -0,0 +1,5 @@
+---
+"webpack": patch
+---
+
+Name an anonymous `export default class` before its static initializers run.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -843,7 +843,7 @@
 
 - Fix snapshot validity check for context dependencies in watch mode by treating watchpack's existence-only entries (`{}`) as cache misses. (by [@alexander-akait](https://github.com/alexander-akait) in [#20916](https://github.com/webpack/webpack/pull/20916))
 
-- Support no-expression template literals in computed member access (e.g. `` import.meta[`url`] ``). (by [@alexander-akait](https://github.com/alexander-akait) in [#20889](https://github.com/webpack/webpack/pull/20889))
+- Support no-expression template literals in computed member access (e.g. ``import.meta[`url`]``). (by [@alexander-akait](https://github.com/alexander-akait) in [#20889](https://github.com/webpack/webpack/pull/20889))
 
 - Improve tree-shaking in `isPure`: handle more expression types (`ArrayExpression`, `ObjectExpression`, `NewExpression`, `ChainExpression`, `UnaryExpression` (safe operators), `MetaProperty`, `TaggedTemplateExpression`, `BinaryExpression` (strict equality)), prevent `/*#__PURE__*/` comments from leaking across `ObjectExpression` properties, and detect PURE comments inside `TemplateLiteral` interpolations. (by [@alexander-akait](https://github.com/alexander-akait) in [#20723](https://github.com/webpack/webpack/pull/20723))
 

diff --git a/lib/dependencies/HarmonyExportDependencyParserPlugin.js b/lib/dependencies/HarmonyExportDependencyParserPlugin.js
@@ -218,14 +218,19 @@ module.exports = class HarmonyExportDependencyParserPlugin {
 						: undefined,
 				constValue
 			);
+			const isAnonymousClass =
+				(node.type === "ClassDeclaration" || node.type === "ClassExpression") &&
+				!node.id;
 			dep.isAnonymousDefault =
 				this.options.anonymousDefaultExportName !== false &&
 				(node.type === "ArrowFunctionExpression" ||
+					isAnonymousClass ||
 					((node.type === "FunctionDeclaration" ||
-						node.type === "FunctionExpression" ||
-						node.type === "ClassDeclaration" ||
-						node.type === "ClassExpression") &&
+						node.type === "FunctionExpression") &&
 						!node.id));
+			// A class observes its own name from a static initializer, which runs
+			// before the name could be patched afterwards, so it is named in place.
+			dep.isAnonymousDefaultClass = dep.isAnonymousDefault && isAnonymousClass;
 			dep.setLocWithIndex(parser.getLocation(statement), -1);
 			parser.state.current.addDependency(dep);
 			getInnerGraphUtils(parser.state.compilation).addVariableUsage(

diff --git a/lib/dependencies/HarmonyExportExpressionDependency.js b/lib/dependencies/HarmonyExportExpressionDependency.js
@@ -26,8 +26,8 @@ const DEFAULT_EXPORT_NAME = "default";
 /** @import { InlinedValue } from "../optimize/InlineExports" */
 /** @import { Range } from "../javascript/JavascriptParser" */
 /** @typedef {string | { id?: string | undefined, range: Range, prefix: string, suffix: string }} DeclarationId */
-/** @typedef {import("../serialization/ObjectMiddleware").ObjectDeserializerContext<[Range, Range, string, DeclarationId | undefined, boolean]>} ObjectDeserializerContext */
-/** @typedef {import("../serialization/ObjectMiddleware").ObjectSerializerContext<[Range, Range, string, DeclarationId | undefined, boolean]>} ObjectSerializerContext */
+/** @typedef {import("../serialization/ObjectMiddleware").ObjectDeserializerContext<[Range, Range, string, DeclarationId | undefined, boolean, boolean]>} ObjectDeserializerContext */
+/** @typedef {import("../serialization/ObjectMiddleware").ObjectSerializerContext<[Range, Range, string, DeclarationId | undefined, boolean, boolean]>} ObjectSerializerContext */
 /** @import { ExportMap } from "./HarmonyExportInitFragment" */
 /**
  * @import {
@@ -54,6 +54,8 @@ class HarmonyExportExpressionDependency extends NullDependency {
 		this.constValue = constValue;
 		/** @type {boolean} */
 		this.isAnonymousDefault = false;
+		/** @type {boolean} */
+		this.isAnonymousDefaultClass = false;
 	}
 
 	get type() {
@@ -126,6 +128,7 @@ class HarmonyExportExpressionDependency extends NullDependency {
 			.write(this.prefix)
 			.write(this.declarationId)
 			.write(this.isAnonymousDefault)
+			.write(this.isAnonymousDefaultClass)
 			.write(this.constValue);
 		super.serialize(context);
 	}
@@ -145,8 +148,10 @@ class HarmonyExportExpressionDependency extends NullDependency {
 		const c4 = c3.rest;
 		this.isAnonymousDefault = c4.read();
 		const c5 = c4.rest;
-		this.constValue = c5.read();
-		super.deserialize(c5.rest);
+		this.isAnonymousDefaultClass = c5.read();
+		const c6 = c5.rest;
+		this.constValue = c6.read();
+		super.deserialize(c6.rest);
 	}
 }
 
@@ -308,6 +313,22 @@ HarmonyExportExpressionDependency.Template = class HarmonyExportDependencyTempla
 			}
 
 			if (dep.range) {
+				// `export default class {}` names the class "default", and a static
+				// initializer reads that name before any later fix-up could run, so
+				// the class is created as a property of that name instead.
+				if (dep.isAnonymousDefaultClass) {
+					source.replace(
+						dep.rangeStatement[0],
+						dep.range[0] - 1,
+						`${content}{ ${DEFAULT_EXPORT_NAME}: (${dep.prefix}`
+					);
+					source.replace(
+						dep.range[1],
+						dep.rangeStatement[1] - 0.5,
+						`) }.${DEFAULT_EXPORT_NAME};`
+					);
+					return;
+				}
 				source.replace(
 					dep.rangeStatement[0],
 					dep.range[0] - 1,

diff --git a/test/configCases/anonymous-default-export-name/class-static-initializer/Thing.js b/test/configCases/anonymous-default-export-name/class-static-initializer/Thing.js
@@ -0,0 +1,5 @@
+export let nameDuringDefinition;
+
+export default class {
+	static observed = (nameDuringDefinition = this.name);
+};
diff --git a/test/configCases/anonymous-default-export-name/class-static-initializer/index.js b/test/configCases/anonymous-default-export-name/class-static-initializer/index.js
@@ -0,0 +1,8 @@
+import Thing, { nameDuringDefinition } from "./Thing";
+
+it("should name an anonymous default class before its static initializers run", () => {
+	// A static initializer reads the name during ClassDefinitionEvaluation, so a
+	// fix-up applied after the class expression is too late to be observed.
+	expect(nameDuringDefinition).toBe("default");
+	expect(Thing.name).toBe("default");
+});
diff --git a/test/configCases/anonymous-default-export-name/class-static-initializer/test.filter.js b/test/configCases/anonymous-default-export-name/class-static-initializer/test.filter.js
@@ -0,0 +1,8 @@
+"use strict";
+
+// The fixture observes the name from a class static field, which Node 10
+// cannot parse when the harness executes the bundle.
+module.exports = function filter() {
+	const major = Number(process.versions.node.split(".")[0]);
+	return major >= 12;
+};
diff --git a/test/configCases/anonymous-default-export-name/class-static-initializer/webpack.config.js b/test/configCases/anonymous-default-export-name/class-static-initializer/webpack.config.js
@@ -0,0 +1,7 @@
+"use strict";
+
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	mode: "development",
+	devtool: false
+};
diff --git a/test/test262.spectest.js b/test/test262.spectest.js
@@ -920,9 +920,6 @@ const knownBugs = [
 	// Potential improvement for enumerate
 	"module-code/namespace/internals/enumerate-binding-uninit.js",
 
-	// Replacing `export default` will remove `default` name by spec, need to `static name = "default";` if doesn't exist
-	"expressions/class/elements/class-name-static-initializer-default-export.js",
-
 	// Tests use `$262.evalScript`/`Object.preventExtensions(this)` to declare
 	// or collide global bindings; webpack wraps each module so `this` is not
 	// the realm's global object and there is no Script Record context.