Add __repr__ for conditions.ConditionBase

[tibbe]

Describe the feature

Add __repr__ for ConditionBase and its subclasses.

Use Case

When writing unit tests using Stubber the error messages are hard to read because if one of the parameter is a ConditionBase we can't see what kind of expression we tried to match on. For example, if we have this in a test:

stubber.add_response('query', {
    'Items': [...]
}, {
    'FilterExpression': Attr('Type').eq('X') & Attr('Type').eq('Y'),
})

A failure will say something like "FilterExpression expected conditions.And, got conditions.And" because Python's default __repr__ only outputs the class name and not the fields so Attr('Type').eq('X') & Attr('Type').eq('Y') and Attr('Type').eq('X') & Attr('Type').eq('Z') pretty-prints exactly the same.

Proposed Solution

Add __repr__ implementations to the classes derived from

boto3/boto3/dynamodb/conditions.py

Line 25 in 3d48469

class ConditionBase:

The string should contain the operator name recursively print the operands. I don't particularly care if it looks like "And(Attr('Type').eq('X'), Attr('Type').eq('Y'))" or something prettier like "Type = X AND Type = Y".

Maybe it can be done using the existing get_expression().

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

SDK version used

1.26.81

Environment details (OS name and version, etc.)

Mac/Linux

[tim-finnigan]

Hello and thanks for the feature request. Similar issues have been opened in the past, for example: #3259. The author of that issue also created a PR (#3254) and the initial feedback there was that the logging could be improved using __repr__. However there is now a feature freeze on updates to boto3 resources (see: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/resources.html). For that reason I don't think this will get prioritized.

[tibbe]

Just a small note that this isn't only for boto3 resources. It affects any code that uses e.g. Key and Attr, including boto3 clients.