Bug: S3Object.closed is False after close() for gzip, and makes S3 calls for zip #8564

Expected Behaviour

After S3Object.close(), S3Object.closed is True. Checking closed does not do any work against S3.

Current Behaviour

S3Object.closed is implemented as self.transformed_stream.closed, and transformed_stream is created lazily. That has two side effects:

1. For an object that was never read, close() only closes the raw stream. A later .closed then builds the transformed stream on top of the already closed raw stream. With is_gzip=True it returns False for an object that was just closed.
2. With a transformation that reads on creation, checking .closed issues S3 requests. ZipTransform reads the archive's central directory, so .closed calls HeadObject and GetObject.

Code snippet

import boto3
from aws_lambda_powertools.utilities.streaming import S3Object

client = boto3.client("s3", region_name="us-east-1", aws_access_key_id="x", aws_secret_access_key="x")

obj = S3Object("bucket", "key", boto3_client=client, is_gzip=True)
obj.close()
print(obj.closed)  # False, expected True

For the zip case, use a botocore Stubber with no queued responses: obj.transform(ZipTransform(), in_place=True); obj.closed raises UnStubbedResponseError for HeadObject.

Possible Solution

When the transformed stream has not been created yet, answer from the raw stream (self.raw_stream.closed) instead of creating it. I have a small fix with tests ready.

Steps to Reproduce

Run the snippet above.

Powertools for AWS Lambda (Python) version

develop (1d4f145, 3.36.0)

AWS Lambda function runtime

3.12

Packaging format used

PyPi

Disclosure: I found this while reviewing the streaming utility with the help of an AI assistant (Claude Code). I ran the snippets above myself against develop.