DynamoDBPersistenceLayer should use ExpressionAttributeNames in _put_record

[Tankanow]

What were you trying to accomplish?

Expected Behavior

I should be able to use DynamoDB reserved words as Item attributes. For example, ttl is a common DynamoDB Item Time to Live attribute name. A consumer should be able to specify reserved word attribute names for any of the *_attr values when configuring DynamoDBPersistenceLayer.

Current Behavior

_put_record currently throws an exception b/c it uses Python string interpolation instead of ExpressionAttributeNames.

Possible Solution

Switch to ExpressionAttributeNames, e.g.

            self.table.put_item(
                Item=item,
                ConditionExpression='attribute_not_exists(#key) OR #now < :now',
                ExpressionAttributeNames={"#key": self.key_attr, "#now": self.expiry_attr},
                ExpressionAttributeValues={":now": int(now.timestamp())},
            )

Steps to Reproduce (for bugs)

1. Create a DynamoDB table with a Time to Live attribute called ttl.
2. Configure a DynamoDBPersistenceLayer with expiry_attr='ttl'
3. Run

Environment

• Powertools version used: 1.20.2
• Packaging format (Layers, PyPi): PyPi
• AWS Lambda function runtime: Python 3.8
• Debugging logs

How to enable debug mode**

# paste logs here

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.

[Tankanow]

I'm happy to submit a PR for this. I have it locally.

[heitorlessa]

Hey @Tankanow, same as the other one -- another oversight from our part, I'd love a PR as it's a quick one.

[heitorlessa]

This is now available as part of today's release 1.21.0 @Tankanow ;) Thank you so much for contributing that!

https://github.com/awslabs/aws-lambda-powertools-python/releases/tag/v1.21.0