[core-amqp] improve error message on TypeError: sendRequest of undefined

sdk/core/core-amqp/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## 2.1.0 (Unreleased)
 
+- Fixes the bug reported in issue [13048](https://github.com/Azure/azure-sdk-for-js/issues/13048).
+  Now an informative error is thrown describing the circumstance that led to the error.
 - Adds the ability to configure the `amqpHostname` and `port` that a `ConnectionContextBase` will use when connecting to a service.
   The `host` field refers to the DNS host or IP address of the service, whereas the `amqpHostname`
   is the fully qualified host name of the service. Normally `host` and `amqpHostname` will be the same.

sdk/core/core-amqp/src/cbs.ts

@@ -190,6 +190,10 @@ export class CbsClient {
     tokenType: TokenType
   ): Promise<CbsResponse> {
     try {
+      if (!this._cbsSenderReceiverLink) {
+        throw new Error("Attempted to negotiate a claim but the CBS link does not exist.");
+      }
+
       const request: RheaMessage = {
         body: token,
         message_id: generate_uuid(),
@@ -201,7 +205,7 @@ export class CbsClient {
           type: tokenType
         }
       };
-      const responseMessage = await this._cbsSenderReceiverLink!.sendRequest(request);
+      const responseMessage = await this._cbsSenderReceiverLink.sendRequest(request);
       logger.verbose("[%s] The CBS response is: %O", this.connection.id, responseMessage);
       return this._fromRheaMessageResponse(responseMessage);
     } catch (err) {

sdk/core/core-amqp/test/cbs.spec.ts

@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+import { assert } from "chai";
+import { Connection } from "rhea-promise";
+import { stub } from "sinon";
+import { CbsClient, TokenType } from "../src";
+
+describe("CbsClient", function() {
+  const TEST_FAILURE = "Test failure";
+  describe("negotiateClaim", function() {
+    it("throws an error if the cbs link doesn't exist.", async function() {
+      const connectionStub = stub(new Connection()) as any;
+
+      const cbsClient = new CbsClient(connectionStub, "lock");
+      try {
+        await cbsClient.negotiateClaim("audience", "token", TokenType.CbsTokenTypeSas);
+        throw new Error(TEST_FAILURE);
+      } catch (err) {
+        assert.equal(
+          err.message,
+          "Attempted to negotiate a claim but the CBS link does not exist."
+        );
+      }
+    });
+  });
+});