fix(NODE-4783): handle orphaned operation descriptions

Author: durran

src/cmap/connection.ts

@@ -369,7 +369,23 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
 
     // always emit the message, in case we are streaming
     this.emit('message', message);
-    const operationDescription = this[kQueue].get(message.responseTo);
+    let operationDescription = this[kQueue].get(message.responseTo);
+
+    if (!operationDescription && this.isMonitoringConnection) {
+      // NODE-4783: How do we recover from this when the initial hello's requestId is not
+      // the responseTo when hello responses have been skipped?
+      //
+      // Get the first orphaned operation description.
+      const entry = this[kQueue].entries().next();
+      if (entry) {
+        const [requestId, orphaned]: [number, OperationDescription] = entry.value;
+        // If the orphaned operation description exists then set it.
+        operationDescription = orphaned;
+        // Remove the entry with the bad request id from the queue.
+        this[kQueue].delete(requestId);
+      }
+    }
+
     if (!operationDescription) {
       return;
     }
@@ -381,7 +397,10 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
     // making the `responseTo` change on each response
     this[kQueue].delete(message.responseTo);
     if ('moreToCome' in message && message.moreToCome) {
-      // requeue the callback for next synthetic request
+      // NODE-4783: If the operation description check above does find an orphaned
+      // description and sets the operationDescription then this line will put one
+      // back in the queue with the correct requestId and will resolve not being able
+      // to find the next one via the responseTo of the next streaming hello.
       this[kQueue].set(message.requestId, operationDescription);
     } else if (operationDescription.socketTimeoutOverride) {
       this[kStream].setTimeout(this.socketTimeoutMS);