fix: preserve custom tap options dropped by _tap fast path

lib/Hook.js

@@ -90,13 +90,17 @@ class Hook {
 			// Fast path: only `name` is set. Build the descriptor as a literal
 			// so `_insert` and downstream consumers see the same hidden class
 			// as the string-options path, avoiding a polymorphic call site.
-			if (
-				options.before === undefined &&
-				options.stage === undefined &&
-				options.context === undefined &&
-				options.type === undefined &&
-				options.fn === undefined
-			) {
+			// Scan with `for...in` (cheaper than allocating `Object.keys`)
+			// to verify no other user-provided properties exist - e.g.
+			// webpack's `additionalAssets` - otherwise they'd be dropped.
+			let onlyName = true;
+			for (const key in options) {
+				if (key !== "name") {
+					onlyName = false;
+					break;
+				}
+			}
+			if (onlyName) {
 				options = { type, fn, name };
 			} else {
 				options.name = name;

test/Hook.test.js

@@ -183,6 +183,23 @@ describe("Hook", () => {
 		);
 	});
 
+	it("should preserve custom tap options (e.g. webpack's `additionalAssets`) on the tap descriptor", () => {
+		const hook = new SyncHook();
+
+		// Options with only `name` plus a custom property - used by webpack's
+		// processAssets (`additionalAssets: true`). The fast-path in `_tap`
+		// must not drop the custom property.
+		hook.tap({ name: "A", additionalAssets: true }, () => {});
+		// Options with `name`, `stage` and a custom property go through the
+		// slow path - also checked for completeness.
+		hook.tap({ name: "B", stage: 10, extra: "value" }, () => {});
+
+		expect(hook.taps[0].name).toBe("A");
+		expect(hook.taps[0].additionalAssets).toBe(true);
+		expect(hook.taps[1].name).toBe("B");
+		expect(hook.taps[1].extra).toBe("value");
+	});
+
 	it("should not ignore invalid before values", () => {
 		// A plugin may use a hook that will never be executed
 		const hook = new SyncHook();