IDynamoDBContext.ToDocument ignores read-only properties

[philBrown]

Description

Read-only POCO properties are ignored when creating a Document using IDynamoDBContext.ToDocument

These properties have values and should be included in the produced Document.

Reproduction Steps

Create a POCO with DynamoDB annotations and a read-only property (Greeting)

public class MyObject
{
    [DynamoDBHashKey("id")]
    public string Id { get; set; }

    [DynamoDBProperty("name")]
    public string Name { get; set; }

    [DynamoDBProperty("greeting")]
    public string Greeting => $"Hello, {Name}"
}

Create a Document and inspect the keys / values

var myobj = new MyObject
{
    Id = "my-id",
    Name = "Phil"
};
Console.WriteLine(myobj.Greeting); // "Hello, Phil"
var context = new DynamoDBContext(ddbclient);
var document = context.ToDocument(myobj);

Console.WriteLine(document.Count); // 2
Console.WriteLine(document.Keys.Contains("id")); // true
Console.WriteLine(document.Keys.Contains("name")); // true
Console.WriteLine(document.Keys.Contains("greeting")); // false

Environment

• SDK Version: AWSSDK.DynamoDBv2 3.3.106.36
• OS Info: Windows 10
• Build Environment: Jetbrains Rider and dotnet CLI
• Targeted .NET Platform: .Net Core 3.1

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This is a 🐛 bug-report

[ashishdhingra]

Hi @philBrown,

Thanks for reporting the issue. From initial analysis, read-only properties appear to be ignored when using IDynamoDBContext.ToDocument(). I will investigate this further and pass on to developer for further inputs.

Thanks,
Ashish

[ashishdhingra]

Hi @philBrown,

Good morning.

I just got an update from development team that the behavior to ignore read-only properties is by design. The code at

aws-sdk-net/sdk/src/Services/DynamoDBv2/Custom/DataModel/InternalModel.cs

Line 303 in 663728f

if (!Utils.IsReadWrite(member))

checks for the valid fields and if the field is not read-write then it treats it as not valid.

Please let me know if this explains the scenario.

Thanks,
Ashish

[philBrown]

Hi @ashishdhingra

Why would ToDocument need to write to a field? I would expect when transforming an object to a Document, that all readable fields, and especially those annotated with DynamoDBProperty would be included.

To compare, if I serialise the object to JSON, all readable fields are included.

[ashishdhingra]

Hi @philBrown,

I agree with you that the read-only fields should also be serialized when using ToDocument(). I'm waiting on developer for the reasoning behind this behavior and would update here once we investigation is done.

Thanks,
Ashish