bug: 'Invalid State Machine Definition' when 'if' condition checks for array existence and length

[dmeehan1968]

Reading message from an SQS Queue, the response.Message property can be undefined, so its normal to check as defined. The length check isn't strictly necessary, and it works without, but the interesting thing is that the error message says "Expected value of type STRING" and "StringGreaterThan".

const main = asl.deploy.asStateMachine(async (input: SQSEvent) => {

    const response = await asl.sdk(SQS).receiveMessage({
        parameters: {
            QueueUrl: asl.deploy.getParameter('QUEUE_URL'),
            MaxNumberOfMessages: 1,
        }
    })

    if (response.Messages !== undefined && response.Messages.length > 0) {
        const messages = (response.Messages).map(message => asl.states.stringToJson(message.Body))

        // ...
    }

})

Full error:

InvalidDefinition: Invalid State Machine Definition: 'SCHEMA_VALIDATION_FAILED: Expected value of type [STRING] at /States/If (response.Messages !== .../Choices[0]/And[1]/StringGreaterThan'