browser-emulator: fix notify-aws.sh: AWS_STACK: unbound variable

Author: ivchicano

browser-emulator/notify-aws.sh

@@ -9,7 +9,21 @@ set -o xtrace
 
 pip3 install --break-system-packages https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-py3-latest.tar.gz
 
+# Ensure AWS_STACK and AWS_REGION are available. If not set in the current
+# environment, try loading them from /etc/environment (CloudFormation writes
+# these there in userdata). Use safe expansions to avoid nounset failures.
+if [ -z "${AWS_STACK:-}" ] || [ -z "${AWS_REGION:-}" ]; then
+	if [ -f /etc/environment ]; then
+		. /etc/environment || true
+	fi
+fi
+
+if [ -z "${AWS_STACK:-}" ] || [ -z "${AWS_REGION:-}" ]; then
+	echo "Required AWS variables AWS_STACK or AWS_REGION not set" >&2
+	exit 1
+fi
+
 # sending the finish call
-cfn-signal -e 0 --stack ${AWS_STACK} --resource BrowserInstance --region ${AWS_REGION}
+cfn-signal -e 0 --stack "${AWS_STACK}" --resource BrowserInstance --region "${AWS_REGION}"
 
 echo "Instance is ready"