Bug: SQSMessageAttribute.binary_value raises KeyError for String attributes #8712

Expected Behaviour

SQSMessageAttribute.string_value and binary_value are typed str | None, so reading the value an attribute doesn't carry should return None.

Current Behaviour

Both properties index the dict directly (self["stringValue"], self["binaryValue"]). Lambda only sends the field that matches the attribute's type; the SQS example event in the Lambda docs has {"stringValue": "myValue", "stringListValues": [], "binaryListValues": [], "dataType": "String"} with no binaryValue. So binary_value on any String or Number attribute, and string_value on any Binary attribute, raise KeyError.

The test event tests/events/sqsEvent.json puts both stringValue and binaryValue on one attribute, which is why the existing tests don't hit this. The Pydantic SqsMsgAttributeModel already declares both fields optional.

Code snippet

from aws_lambda_powertools.utilities.data_classes import SQSEvent

event = {"Records": [{
    "messageId": "1", "receiptHandle": "r", "body": "b", "attributes": {}, "md5OfBody": "m",
    "eventSource": "aws:sqs", "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:q", "awsRegion": "us-east-2",
    "messageAttributes": {
        "text": {"stringValue": "myValue", "stringListValues": [], "binaryListValues": [], "dataType": "String"},
    },
}]}
record = next(SQSEvent(event).records)
record.message_attributes["text"].binary_value  # KeyError: 'binaryValue'

Steps to Reproduce

1. Send an SQS message with a String message attribute to a Lambda function.
2. Read binary_value on that attribute (or string_value on a Binary one).
3. KeyError is raised instead of None.

Possible Solution

Use self.get(...) in both properties. I can open a PR.

Powertools for AWS Lambda (Python) version

latest (develop, 3.38.0)

AWS Lambda function runtime

3.12

Packaging format used

PyPi

Debugging logs

No response