DynamoDB.SourceGenerator

This source generator is crafted to simplify DynamoDB integration for your projects. It's designed to effortlessly generate the low-level DynamoDB API tailored to any DTO you provide.

Note

This project has not been tested in any real scenario and currently serves as a hobby project.

Installation

If you want access to more high level reusable abstractions, utilizing builder patterns from the functionality of this library, check out Dynatello!

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Install the following dependencies:

The DynamoDBGenerator.SourceGenerator is where the source generator is implemented. The source generator will look for attributes and implement interfaces that exists in DynamoDBGenerator.

Goals:

• Seamless Developer Interaction (DevEx): Experience a hassle-free DynamoDB interaction where the generated code handles the heavy lifting, ensuring an intuitive and convenient experience for developers.
  • Simplify Attribute Expressions: Easily create complex expressions with an intuitive approach.
• Faster performance: Utilize the low-level API that would normally be implemented manually.

Features:

• Reflection-Free Codebase: The generated code is built without reliance on reflection, ensuring compatibility with Ahead-of-Time (AOT) compilation: This translates to faster startup times and a more efficient memory footprint.
• Nullable Reference type support: Embrace modern coding practices with support for Nullable Reference Types. Effortlessly handle optional values and ensure robust error handling.
• Marshalling: Seamlessly convert your DTO into DynamoDB types.
• Unmarshalling: Seamlessly convert DynamoDB types into your DTO.
  • Constructor support: Leverage constructors in your DTOs.
• Marshalling keys: Seamlessly convert values into DynamoDB key types by decorating your properties with DynamoDbKeysAttributes.
  • HashKey and RangeKey ✔
  • GlobalSecondaryIndex ✔
  • LocalSecondaryIndex ✔
• Custom Converters: Create converters for your own types or override the default converters built in to the library.
• ValueTuple<T> support: You don't have to declare your own types and could instead use tuples with custom named fields that will act as if the tuple was a type with with those data members.

Conversion

Primitive Types

Type	Field
bool	BOOL
char	S
int	N
long	N
string	S
uint	N
ulong	N
Guid	S
Enum	N

Binary

Type	Field
MemoryStream	B

Temporal Types

Type	Field	Format
DateOnly	S	ISO 8601
TimeOnly	S	ISO 8601
DateTime	S	ISO 8601
DateTimeOffset	S	ISO 8601
TimeSpan	S	ISO 8601

Collection Types

Type	Field	Description
ICollection<T>	L
IDictonary<string, TValue>	M	Will treat the Dictionary as a Key-Value store.
IEnumerable<T>	L
IReadOnlyList<T>	L
IRedonlyDictionary<string, TValue>	M	Will treat the Dictionary as a Key-Value store.
ILookup<string, TValue>	M	Will treat the ILookup as a Key-Values store.
ISet<int>	NS
ISet<long>	NS
ISet<string>	SS
ISet<uint>	NS
ISet<ulong>	NS
T[]	L

Custom types

Types not listed above will be treated as an object by being assigned to the M field

Reference Tracker

As part of the source generation process, two additional types will be mirrored to the provided DTO:

• A reference tracker that serves as attribute references on DynamoDB side.
• A reference tracker that functions as attribute references for the arguments you provide to DynamoDB.

These trackers enable you to consistently construct your AttributeExpressions using string interpolation. For an illustrative example, refer to the tests.

Nullable reference types

The source-generated code will adapt to your NullableReference types if you have it enabled.

Examples

#nullable enable
// The following would be considered to be optional.
public string? MyOptionalString { get; set; }
// The following would be considered required and throw DynamoDBMarshallingException if the value was not provided.
public string MyRequiredString { get; set; }
#nullable disable
// The following does not have nullable enabled and would consider the string to be optional.
public string MyUnknownString { get; set; }

Code examples

An example DTO class could look like the one below. The following examples will use this sample class.

public class Person
{
    // Will be included as 'PK' in DynamoDB.
    [DynamoDBHashKey("PK")]
    public string Id { get; set; }

    // Will be included as 'Firstname' in DynamoDB.
    public string Firstname { get; set; }

    // Will be included as 'Contact' in DynamoDB.
    [DynamoDBProperty("Contact")]
    public Contact ContactInfo { get; set; }

    // Wont be included in DynamoDB.
    [DynamoDBIgnore]
    public string FirstNameLowercase => Firstname.ToLower();

    public class Contact
    {
        // Will be included as 'Email' in DynamoDB.
        public string Email { get; set;}
    }
}

Creating request objects

UpdateRequest without providing the DTO

// A typical scenario would be that you would use multuple DynamoDBMarshaller and describe your operaitons via AccessName.
// If you do not specify an ArgumentType it will use your main entity Type instead which is typically useful for PUT operations.
[DynamoDBMarshaller(EntityType = typeof(Person), ArgumentType = typeof((string PersonId, string Firstname)), AccessName = "UpdateFirstName")]
public partial class Repository { }

internal static class Program
{
    public static void Main()
    {
        Repository repository = new Repository();

        // Creating an AttributeExpression can be done through string interpolation where the source generator will mimic your DTO types and give you an consistent API to build the attributeExpressions.
        var attributeExpression = repository.UpdateFirstName.ToAttributeExpression(
          ("personId", "John"),
          (dbRef, argRef) => $"{dbRef.Id} = {argRef.PersonId}", // The condition
          (dbRef, argRef) => $"SET {dbRef.Firstname} = {argRef.FirstName}" // The update operation
        );

        // the index can be used to retrieve the expressions in the same order as you provide the string interpolations in the method call above.
        var condition = attributeExpression.Expressions[0];
        var update = attributeExpression.Expressions[1];
        var keys = repository.UpdateFirstName.PrimaryKeyMarshaller.PartitionKey("personId");

        var request = new UpdateItemRequest
        {
            ConditionExpression = condition,
            UpdateExpression = update,
            ExpressionAttributeNames = attributeExpression.Names,
            ExpressionAttributeValues = attributeExpression.Values,
            Key = keys,
            TableName = "MyTable"
        }
    }
}

Key conversion

The key marshallers contain three methods based on your intent. The source generator will internally validate your object arguments. So if you pass a int but the actual key is represented as a string, then you will get an exception.

• Keys(object partitionKey, object rangeKey)
  • Used when you want convert both a partion key and a range key.
• PartionKey(object key)
  • Used when you only want to only convert a partiton key without a range key.
• RangeKey(object key)
  • Used when you only want to only convert a range key without a partition key.

[DynamoDBMarshaller(AccessName = 'KeyMarshallerSample')]
public class EntityDTO
{
    [DynamoDBHashKey("PK")]
    public string Id { get; set; }

    [DynamoDBRangeKey("RK")]
    public string RangeKey { get; set; }

    [DynamoDBLocalSecondaryIndexRangeKey("LSI")]
    public string SecondaryRangeKey { get; set; }

    [DynamoDBGlobalSecondaryIndexHashKey("GSI")]
    public string GlobalSecondaryIndexId { get; set; }

    [DynamoDBGlobalSecondaryIndexRangeKey("GSI")]
    public string GlobalSecondaryIndexRangeKey { get; set; }
}
internal static class Program
{
    public static void Main()
    {
        // PrimaryKeyMarshaller is used to convert the keys obtained from the [DynamoDBHashKey] and [DynamoDBRangeKey] attributes.
        var keyMarshaller = EntityDTO.KeyMarshallerSample.PrimaryKeyMarshaller;

        // IndexKeyMarshaller requires an argument that is the index name so it can provide you with the correct conversion based on the indexes you may have.
        // It works the same way for both LocalSecondaryIndex and GlobalSecondaryIndex attributes.
        var GSIKeyMarshaller = EntityDTO.KeyMarshallerSample.IndexKeyMarshaller("GSI");
        var LSIKeyMarshaller = EntityDTO.KeyMarshallerSample.IndexKeyMarshaller("LSI");
    }
}

Configuring the marshaller

Custom converters

// Implement an converter, there's also an IReferenceTypeConverter available for ReferenceTypes.
public class UnixEpochDateTimeConverter : IValueTypeConverter<DateTime>
{
    // Convert the AttributeValue into a .NET type.
    public DateTime? Read(AttributeValue attributeValue)
    {
        return long.TryParse(attributeValue.N, out var epoch) ? DateTimeOffset.FromUnixTimeSeconds(epoch).DateTime : null;
    }

    // Convert the .NET type into an AttributeValue.
    public AttributeValue Write(DateTime element)
    {
        return new AttributeValue { N = new DateTimeOffset(element).ToUnixTimeSeconds().ToString() };
    }
}
// Create a new Converters class
// You don't have to inherit from AttributeValueConverters if you do not want to use the default converters provided.
public class MyCustomConverters : AttributeValueConverters
{
    // If you take constructor parameters, the source generator will recongnize it and change the way you access it into an method.
    // It's recommended to call the method once and save it into a class member.
    public MyCustomConverters()
    {
        // Override the default behaviour.
        DateTimeConverter = new UnixEpochDateTimeConverter();
    }
    // You could add more converter DataMembers as fields or properties to add your own custom conversions.

}

[DynamoDBMarshallerOptions(Converter = typeof(MyCustomConverters))]
[DynamoDBMarshaller(EntityType = typeof(Person), AccessName = "PersonMarshaller")]
public partial Repository 
{

}

Enum conversion

[DynamoDBMarshallerOptions(EnumConversion = EnumConversion.Name)]
[DynamoDBMarshaller(EntityType = typeof(Person), AccessName = "PersonMarshaller")]
public partial class Repository { }

Project structure

The DynamoDBGenerator assembly contains functionality that the DynamoDBGenerator.SourceGenerator rely on such as the attribute that will trigger the source generation. In other words both assemblies needs to be installed in order for the source generator to work as expected.