aws_stepfunctions_tasks: DynamoAttributeValue.fromStringSet requires an array

[dbartholomae]

Describe the bug

When creating a JsonPath value, it returns a string even for arrays, but DynamoAttributeValue.fromStringSet needs a string array.

    const releaseSlot = new DynamoUpdateItem(this, "ReleaseSlot", {
      key: {
        [partitionKey]: DynamoAttributeValue.fromString(fixedKey),
      },

      updateExpression: `DELETE ${workflowsKey} :val`,
      expressionAttributeValues: {
        ":val": DynamoAttributeValue.fromStringSet(
          JsonPath.array(
            JsonPath.stringAt("$$.Execution.Id")
          ) as unknown as string[]
        ),
      },
      table: slots,
    });

Expected Behavior

This should work without the as unknown as string[] cast

Current Behavior

as unknown as string[] cast is required

Reproduction Steps

The code above without the cast will cause the TypeScript error.

Possible Solution

Accept a string or string[]. This would be non-breaking.

Additional Information/Context

No response

CDK CLI Version

2.80.0

Framework Version

No response

Node.js Version

16.14.2

OS

Mac

Language

Typescript

Language Version

5.0.4

Other information

No response

[peterwoodworth]

Since JsonPath.array returns a string, you can specify the JsonPath.array to be in an array like so:

    new tasks.DynamoUpdateItem(this, 'UpdateItem', {
      key: {
        MessageId: tasks.DynamoAttributeValue.fromString('message-007')
      },
      table: table,
      expressionAttributeValues: {
        ':val': tasks.DynamoAttributeValue.fromStringSet([sfn.JsonPath.array(sfn.JsonPath.stringAt('$.messageIds'))]),
        ':rand': tasks.DynamoAttributeValue.fromNumber(20),
      },
      updateExpression: 'SET TotalCount = :val + :rand',
    });

Accept a string or string[]. This would be non-breaking.

I think that with our current implementation, accepting just a string would never work. It looks to me like we will create the stringset definition with whatever is given since we're only expecting a string array. Additionally, I'm pretty sure we can't have union types because of the other languages https://github.com/aws/aws-cdk/blob/cdafcc52ad4aea3ef7f1446da7521fb504cb33b9/packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/dynamodb/shared-types.ts#L165-L167

[dbartholomae]

My current implementation works on runtime and just fails on compile time. Unfortunately, your suggested solution doesn't: https://github.com/aws/aws-cdk/blob/cdafcc52ad4aea3ef7f1446da7521fb504cb33b9/packages/aws-cdk-lib/aws-stepfunctions/lib/private/json-path.ts#L190

JsonPath can't be used inside an array :(

You are right that unions won't work with jsii, though. Maybe an additional method?

[peterwoodworth]

You're right, I didn't actually attach the task when synthesizing before.

Maybe an additional method?

I think it would probably be best if we can create a new method and deprecate the old one, I'm not too sure exactly what this would look like however

[dbartholomae]

How about JsonPath.arrayString? I'm not sure if we can deprecate the old one - if it is used at all, then the new one won't actually work in the other usecase which most likely expects an array.

[dbartholomae]

This was discussed in the first CDK office hours with @mrgrain

Should this be a p1 as type assignments won't work in other languages?