fix: catch error types based on class name

packages/core/strapi/src/middlewares/errors.ts

@@ -3,6 +3,28 @@ import type { Common } from '@strapi/types';
 
 import { formatApplicationError, formatHttpError, formatInternalError } from '../services/errors';
 
+// NOTE: The error.name check is not necessary in the v5 branch!
+// Therefore it should be considered a hack workaround for an actual bug which means that there is a bug
+// somewhere else in the code.
+// The issue is most likely somewhere where ValidationErrors are being created that are not
+// instanceof errors.ApplicationError despite actually being ApplicationErrors.
+//
+// This code is only included because v4 is in maintenance mode and this is a safe fix, but does not solve the
+// root cause of the problem.
+export function isErrorOfTypeOrSubclass<T>(
+  error: any,
+  constructor: { new (...args: any[]): T }
+): error is T {
+  let proto = error?.constructor;
+  while (proto) {
+    if (proto.name === constructor.name) {
+      return true;
+    }
+    proto = Object.getPrototypeOf(proto);
+  }
+  return false;
+}
+
 const errorMiddleware: Common.MiddlewareFactory = (/* _, { strapi } */) => {
   return async (ctx, next) => {
     try {
@@ -12,14 +34,14 @@ const errorMiddleware: Common.MiddlewareFactory = (/* _, { strapi } */) => {
         return ctx.notFound();
       }
     } catch (error) {
-      if (error instanceof errors.ApplicationError) {
+      if (isErrorOfTypeOrSubclass(error, errors.ApplicationError)) {
         const { status, body } = formatApplicationError(error);
         ctx.status = status;
         ctx.body = body;
         return;
       }
 
-      if (error instanceof errors.HttpError) {
+      if (isErrorOfTypeOrSubclass(error, errors.HttpError)) {
         const { status, body } = formatHttpError(error);
         ctx.status = status;
         ctx.body = body;