UpdateItemAsync - DynamoDB Exception: ExpressionAttributeValues must not be empty, even when there are no variables

[elias-visma]

Describe the bug

This bug is similar to #3802 (could not use conditional expressions without supplying ExpressionAttributeValues in PutItemAsync()) which has been fixed (#3804) but the issue remains for UpdateItemAsync(). This worked in V3 of the SDK (AWSSDK.DynamoDBv2 3.7.404.11)

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

The operation should succeed as it did with V3 of the SDK.

Current Behavior

The operation throws the following exception:
AmazonDynamoDBException: ExpressionAttributeValues must not be empty
The behavior is the same, even if ExpressionAttributeValues is explicitly set to null or an empty collection.

Reproduction Steps

await table.UpdateItemAsync(document, new UpdateItemOperationConfig
{
    ConditionalExpression = new Expression { ExpressionStatement = "attribute_not_exists(pk)" }
};

Possible Solution

Two workarounds:
Setting
Amazon.AWSConfigs.InitializeCollections = true;
or
including unnecessary values in ExpressionStatement and ExpressionAttributeValues.

The solution for PutItemAsync() was solved in (#3804)

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWSSDK.DynamoDBv2 4.0.6.4

Targeted .NET Platform

.Net 8

Operating System and version

Windows 11

[dscpinheiro]

This was a miss on that PR, I assumed update item would go through the same code path but obviously it doesn't.

Until we fix it, the InitializeCollections config is the best option to keep using V4.

[dscpinheiro]

@elias-visma Actually do you have a longer reproduction code you can share? I just tried this on latest V3 but it also failed so I may be missing something (Invalid UpdateExpression: The expression can not be empty):

var ddb = new AmazonDynamoDBClient(new AmazonDynamoDBConfig
{
    RegionEndpoint = RegionEndpoint.USWest2,
    MaxErrorRetry = 0,
});

var table = new TableBuilder(ddb, "TestTable").AddHashKey("pk", DynamoDBEntryType.String).Build();
var document = new Document { ["pk"] = Guid.NewGuid().ToString() };

await table.UpdateItemAsync(document, new UpdateItemOperationConfig
{
    ConditionalExpression = new Expression { ExpressionStatement = "attribute_not_exists(pk)" },
});

[elias-visma]

This reproduces the error (edit: it does not, see #4144 (comment) for how to properly reproduce) in AWSSDK.DynamoDBv2 version 4.0.6.4 but works when using version 3.7.404.11 @dscpinheiro

        var pk = "pk";
        var sk = "sk";
        var currentVersionAttr = "currentVersion";
        var doc = new Document
        {
            [pk] = "test",
            [sk] = "testing",
            [currentVersionAttr] = "first version"
        };

        using var client = new AmazonDynamoDBClient();

        var table = new TableBuilder(client, "TestTable")
            .AddHashKey(pk, DynamoDBEntryType.String)
            .AddRangeKey(sk, DynamoDBEntryType.String)
            .Build();

        var config = new UpdateItemOperationConfig
        {
            ConditionalExpression = new Expression
            {
                ExpressionStatement = "attribute_not_exists(updateVersion)",
            }
        };

        await table.UpdateItemAsync(doc, config);

[dscpinheiro]

@elias-visma I'm so sorry, but I still cannot reproduce the error... I even tried to add some logging but the request the SDK is sending seems to be the same in V3 and V4.

using var client = new AmazonDynamoDBClient(new AmazonDynamoDBConfig
{
    HttpClientFactory = new CustomHttpClientFactory(),
});

// Your example.

class CustomHttpClientFactory : HttpClientFactory
{
    public override HttpClient CreateHttpClient(IClientConfig clientConfig)
        => new(new LoggingHandler(new HttpClientHandler()));
}

class LoggingHandler(HttpMessageHandler innerHandler) : DelegatingHandler(innerHandler)
{
    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        Console.WriteLine("======================");
        Console.WriteLine("Canonical request:");
        Console.WriteLine(request.ToString());
        Console.WriteLine("======================");

        if (request.Content != null)
        {
            Console.WriteLine("======================");
            Console.WriteLine("Request content: ");
            Console.WriteLine(await request.Content.ReadAsStringAsync(cancellationToken));
            Console.WriteLine("======================");
        }

        return await base.SendAsync(request, cancellationToken);
    }
}

I tested in 3.7.404.11, 4.0.6.4, and 4.0.10.1 (latest V4) and all of them had the same request:

{
    "ConditionExpression": "attribute_not_exists(updateVersion)",
    "ExpressionAttributeNames": {
        "#awsavar1": "currentVersion"
    },
    "ExpressionAttributeValues": {
        ":awsavar1": {
            "S": "first version"
        }
    },
    "Key": {
        "pk": {
            "S": "test"
        },
        "sk": {
            "S": "testing"
        }
    },
    "ReturnValues": "NONE",
    "TableName": "TestTable",
    "UpdateExpression": "SET #awsavar1 = :awsavar1"
}

If you enable the debug logging, do you see different requests? I don't think it'd impact but for reference here's the table I used:

PS> aws dynamodb describe-table --table-name TestTable
{
    "Table": {
        "AttributeDefinitions": [
            {
                "AttributeName": "pk",
                "AttributeType": "S"
            },
            {
                "AttributeName": "sk",
                "AttributeType": "S"
            }
        ],
        "TableName": "TestTable",
        "KeySchema": [
            {
                "AttributeName": "pk",
                "KeyType": "HASH"
            },
            {
                "AttributeName": "sk",
                "KeyType": "RANGE"
            }
        ],
/// everything else was the default