Kafka.Autofill 0.9.6

Kafka.Autofill

A C# source generator and analyzer for Apache Avro serialization in Kafka. Automatically generates Get() and Put() methods and Avro schemas for ISpecificRecord implementations.

Features

Automatic Code Generation - Generates boilerplate serialization code
Live Validation - Real-time errors for unsupported types in the IDE
Schema Generation - Optionally generates Avro schemas at compile time
Type Safety - Compile-time validation of property types
Zero Runtime Dependencies - Only development-time dependency

Quick Start

1. Mark your class with [KafkaAutofill]

using Kafka.Autofill;
using Avro.Specific;

[KafkaAutofill] // Generates Get(), Put(), and Schema
public partial class Person : ISpecificRecord
{
    public int Age { get; set; }
    public string Name { get; set; } = string.Empty;
    public DateTime BirthDate { get; set; }
    public List<string> Hobbies { get; set; } = [];
}

2. The source generator creates

public partial class Person
{
    private static readonly Schema Cached = Schema.Parse(AvroSchemaGen.GenerateSchema(typeof(Person)));

    [AvroIgnore]
    public Schema Schema { get; } = Cached;

    public object Get(int fieldPos)
    {
        return fieldPos switch
        {
            0 => Age,
            1 => Name,
            2 => BirthDate,
            3 => Hobbies,
            _ => throw new ArgumentOutOfRangeException(...)
        };
    }

    public void Put(int fieldPos, object fieldValue)
    {
        switch (fieldPos)
        {
            case 0: Age = (int)fieldValue; break;
            case 1: Name = (string)fieldValue; break;
            case 2: BirthDate = (DateTime)fieldValue; break;
            case 3: Hobbies = (List<string>)fieldValue; break;
            default: throw new ArgumentOutOfRangeException(...);
        }
    }
}

Supported Types

Primitives

• int, long, float, double, bool, string
• uint (serialized as long)
• ulong (serialized as bytes)
• decimal (serialized as double)
• byte[]
• Guid (uuid)

Date/Time

• DateTime (timestamp-millis)
• DateTimeOffset (timestamp-millis)
• DateOnly (timestamp-millis)

Collections

• T[] - Arrays
• List<T>, HashSet<T>
• IEnumerable<T>, ICollection<T>, IList<T>
• Dictionary<string, T>, IDictionary<string, T> (string keys only)

Complex Types

• User-defined classes and structs
• Enums
• Nullable types: int?, DateTime?, MyEnum?

Nested Types

[KafkaAutofill]
public partial class Person : ISpecificRecord
{
    public string Name { get; set; } = string.Empty;
    public Address HomeAddress { get; set; } = new();
    public List<Address> PreviousAddresses { get; set; } = [];
}

[KafkaAutofill]
public partial class Address : ISpecificRecord
{
    public string Street { get; set; } = string.Empty;
    public string City { get; set; } = string.Empty;
}

Live Type Validation

The analyzer provides real-time errors for unsupported types:

[KafkaAutofill]
public partial class MyClass : ISpecificRecord
{
    // ❌ ERROR: Type 'HttpClient' from namespace 'System.Net.Http' is not supported in Avro schema
    public HttpClient Client { get; set; }
    
    // ❌ ERROR: Delegate type 'Func' from namespace 'System' is not supported in Avro schema
    public Func<string, int> Converter { get; set; }
}

Excluding Properties

Use [AvroIgnore] to exclude properties from serialization:

[KafkaAutofill]
public partial class Person : ISpecificRecord
{
    public string Name { get; set; } = string.Empty;
    
    [AvroIgnore]
    public Func<string, int> Converter { get; set; } // Won't be serialized
}

Schema Generation Options

Generate schema (default)

[KafkaAutofill] // or [KafkaAutofill(true)]
public partial class Person : ISpecificRecord { }

Skip schema generation

[KafkaAutofill(false)]
public partial class Person : ISpecificRecord { }

Requirements

• .NET Standard 2.1 or later
• C# 9.0 or later (for source generators)
• Apache.Avro NuGet package (for runtime)

Contributing

Contributions are welcome! Please open an issue or pull request on GitHub.

License

MIT License - see LICENSE for details.