More defensive programming on values returned from AWS API

Co-authored-by: Copilot <[email protected]>

Author: andrew-nowak

src/aws/autoscaling.ts

@@ -32,7 +32,13 @@ export async function launchNewInstance(instance: Instance, asgName: string): Pr
             `getting current capacity in ${asgName}`,
             5,
         );
+        if (!asgs.AutoScalingGroups || asgs.AutoScalingGroups.length === 0) {
+            throw new Error(`No AutoScalingGroup found with name ${asgName}`);
+        }
         const capacity = asgs.AutoScalingGroups[0].DesiredCapacity;
+        if (typeof capacity !== 'number' || isNaN(capacity)) {
+            throw new Error(`DesiredCapacity is not defined or not a number for ASG ${asgName}`);
+        }
 
         return retry(
             () => awsAutoscaling.send(new SetDesiredCapacityCommand({

src/getTargetNode.ts

@@ -7,7 +7,11 @@ import {Instance} from "./aws/types";
 import { type AutoScalingGroup } from '@aws-sdk/client-auto-scaling';
 
 function asgTagsToRecord(asg: AutoScalingGroup): Record<string, string> {
-  return Object.fromEntries(asg.Tags.map(tag => ([tag.Key, tag.Value])));
+  return Object.fromEntries(
+    (asg.Tags ?? [])
+      .filter(tag => tag.Key !== undefined && tag.Value !== undefined)
+      .map(tag => [tag.Key!, tag.Value!])
+  );
 }
 
 /** attempt to find an ASG with the same tagging as the target instance's,