fix: #15967 Show better error when wrong variable is used in custom event name (#15974)

* update to show exact err msg with custom event name

* updated tests for validateCustomEventName

---------

Co-authored-by: Keith Williams <keithwillcode@gmail.com>
Co-authored-by: Anik Dhabal Babu <81948346+anikdhabal@users.noreply.github.com>

packages/core/event.test.ts

@@ -356,7 +356,7 @@ describe("event tests", () => {
 
   describe("fn: validateCustomEventName", () => {
     it("should be valid when no variables used", () => {
-      expect(event.validateCustomEventName("foo", "error message")).toBe(true);
+      expect(event.validateCustomEventName("foo")).toBe(true);
     });
 
     [
@@ -371,24 +371,24 @@ describe("event tests", () => {
       "USER",
     ].forEach((value) => {
       it(`should support {${value}} variable`, () => {
-        expect(event.validateCustomEventName(`foo {${value}} bar`, "error message")).toBe(true);
+        expect(event.validateCustomEventName(`foo {${value}} bar`)).toBe(true);
 
-        expect(event.validateCustomEventName(`{${value}} bar`, "error message")).toBe(true);
+        expect(event.validateCustomEventName(`{${value}} bar`)).toBe(true);
 
-        expect(event.validateCustomEventName(`foo {${value}}`, "error message")).toBe(true);
+        expect(event.validateCustomEventName(`foo {${value}}`)).toBe(true);
       });
     });
 
     it("should support booking field variables", () => {
       expect(
-        event.validateCustomEventName("foo{customField}bar", "error message", {
+        event.validateCustomEventName("foo{customField}bar", {
           customField: true,
         })
       ).toBe(true);
     });
 
-    it("should return error when invalid variable used", () => {
-      expect(event.validateCustomEventName("foo{nonsenseField}bar", "error message")).toBe("error message");
+    it("should return variable when invalid variable used", () => {
+      expect(event.validateCustomEventName("foo{nonsenseField}bar")).toBe("{nonsenseField}");
     });
   });
 });

packages/core/event.ts

@@ -100,11 +100,7 @@ export function getEventName(eventNameObj: EventNameObjectType, forAttendeeView
   return dynamicEventName;
 }
 
-export const validateCustomEventName = (
-  value: string,
-  message: string,
-  bookingFields?: Prisma.JsonObject
-) => {
+export const validateCustomEventName = (value: string, bookingFields?: Prisma.JsonObject) => {
   let customInputVariables: string[] = [];
   if (bookingFields) {
     customInputVariables = Object.keys(bookingFields).map((customInput) => {
@@ -131,7 +127,7 @@ export const validateCustomEventName = (
   if (matches?.length) {
     for (const item of matches) {
       if (!validVariables.includes(item)) {
-        return message;
+        return item;
       }
     }
   }