Improve error message for the most common user error

src/constructs/aws/Queue.ts

@@ -17,6 +17,7 @@ import { pollMessages, retryMessages } from "./queue/sqs";
 import { sleep } from "../../utils/sleep";
 import { PolicyStatement } from "../../CloudFormation";
 import type { CliOptions } from "../../types/serverless";
+import ServerlessError from "../../utils/error";
 
 const QUEUE_DEFINITION = {
     type: "object",
@@ -109,6 +110,16 @@ export class Queue extends AwsConstruct {
     ) {
         super(scope, id);
 
+        // This should be covered by the schema validation, but until it is enforced by default
+        // this is a very common error for users
+        // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+        if (configuration.worker === undefined) {
+            throw new ServerlessError(
+                `Invalid configuration in 'constructs.${this.id}': no 'worker' defined. Queue constructs require a 'worker' function to be defined.`,
+                "LIFT_INVALID_CONSTRUCT_CONFIGURATION"
+            );
+        }
+
         // The default function timeout is 6 seconds in the Serverless Framework
         const functionTimeout = configuration.worker.timeout ?? 6;