[wrangler] Prevent concurrent custom builds when multiple files change

.changeset/polite-apes-study.md

@@ -0,0 +1,5 @@
+---
+"wrangler": patch
+---
+
+Prevent concurrent custom builds when multiple files change simultaneously

packages/wrangler/src/api/startDevWorker/BundlerController.ts

@@ -208,10 +208,13 @@ export class BundlerController extends Controller<BundlerControllerEventMap> {
 			void this.#runCustomBuild(config, String(pathsToWatch));
 		});
 
-		this.#customBuildWatcher.on(
-			"all",
-			(_event, filePath) => void this.#runCustomBuild(config, filePath)
+		const debouncedRunCustomBuild = debounce(
+			(_event: string, filePath: string) =>
+				void this.#runCustomBuild(config, filePath),
+			50
 		);
+
+		this.#customBuildWatcher.on("all", debouncedRunCustomBuild);
 	}
 
 	#bundlerCleanup?: ReturnType<typeof runBuild>;

packages/wrangler/src/utils/debounce.ts

@@ -3,16 +3,20 @@
  * `delayMs` milliseconds have elapsed since the last time the debounced
  * function was invoked.
  */
-export function debounce(fn: () => void, delayMs = 100) {
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export function debounce<T extends (...args: any[]) => void>(
+	fn: T,
+	delayMs = 100
+): (...args: Parameters<T>) => void {
 	let crrTimeoutId: NodeJS.Timeout | undefined;
 
-	return () => {
+	return (...args: Parameters<T>) => {
 		if (crrTimeoutId) {
 			clearTimeout(crrTimeoutId);
 		}
 
 		crrTimeoutId = setTimeout(() => {
-			fn();
+			fn(...args);
 		}, delayMs);
 	};
 }