InterfaceFillerCodeGen 5.0.0

InterfaceFiller - Aspect Oriented Programming (AOP) in C# (AOT support)

The most minimal and concise but fully features AOP library in C#. All junk codes are 4 custom attributes:

- InterfaceFiller(params string[] wrappers)
- Wrapper()
- CallerParamByIndex(int value, bool fromEnd = false)
- CallerParamByName(string paramName)

Support:

• AOT
• Async (await) method
• C# Caller attribute and two more
• Roslyn analyzers

Within minutes reading, all magic is revealed by 'Find all References'.

Table of content:

• 1. InterfaceFiller attribute

• 2. Wrapper attribute

• 3. Wrapper parameters

• [4. Wrapper parameters resolution]

• [5. Wrapper return]

• 6. Wrapper (with parameter) for Task method

• 7. Wrapper (with parameter) for Task<TResult> method

• 8. C# Caller attributes

• 9. CallerParamByName and CallerParamByIndex attributes

• [10. Wrapper resolution in summary]

• 11. Reuse your Wrapper logic

• Void method

• Issue Report

Changelog

[5.0.0] - 2024-03-09

Added

• Wrapper method returning type is supported.

[3.1.0] - 2023-12-04

Added

• Reuse your Wrapper logic

[3.0.1] - 2023-11-22

Added

• CallerParamByName and CallerParamByIndex attributes

Updated

• Nuget package model but backward compatible

[2.0.1] - 2023-08-28 - Breaking Change to version 1.1.x

Added

• Support C# Caller attributes

Deprecated

• [string methodName]

[1.1.0] - 2023-08-10

Added

• [string methodName]

Specification

1. InterfaceFiller attribute

public interface ITestApi
{
    int FunA(int x, int y);
    Task<StreamContent> FunB(Barrier barrier, Random randomAccess);
}

The must be partial TestApi class, contains testApi backup field (ITestApi type).

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }
}

TestApi has no implementation for interface ITestApi but no compiler error because InterfaceFiller attribute marks to auto-generate the default implementation using the backup field testApi.

// auto-generated
namespace WrapperNormal1
{
    partial class TestApi
    {
        [InterfaceFillerCodeGen.IFCodeGen]
        public int FunA(int x, int y)
        {
            var f1 = this.testApi.FunA;
            
            return f1(x, y);
        }

        [InterfaceFillerCodeGen.IFCodeGen]
        public async System.Threading.Tasks.Task<System.Net.Http.StreamContent> FunB(System.Threading.Barrier barrier, System.Random randomAccess)
        {
            var f1 = this.testApi.FunB;
            
            return await f1(barrier, randomAccess);
        }
    }

}

Note

• Class must be partial
• Class must have backup-field which field type is same as the interface type.
• Backup-field has [InterfaceFiller] attribute.
• If there is an implementation for a method, code-gen will skips.

2. Wrapper attribute

'Aspect' your interface with custom behavior before and/or after execution.

2.1 Normal method

Note: Normal method is the method NOT returns Task or Task<T>

public interface ITestApi
{
    int FunA(int x);
    string FunB(int x, string y);
}

public class ApiClient : ITestApi
{
    public int FunA(int x) => x;
    public string FunB(int x, string y) => $"{x} {y}";
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper<T>(Func<T> next)
    {
        Console.WriteLine("Hello");
        var r = next();
        Console.WriteLine(r);
        Console.WriteLine("World");
        return r;
    }
}

Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1)
//Output:
// Hello
// 1
// World

api.FunB(1, "SJC")
//Output:
// Hello
// 1 SJC
// World

Wrapper method:

• Having [Wrapper] attribute
• The wrapper's return type must be convertible to wrapped's return type (in this case, the type int is convertible to the generic type T)
• The wrapper must have a Func<> parameter

2.2 Task method

public interface ITestApi
{
    Task FunA(int x);
    Task FunB(int x, string y);
}

public class ApiClient : ITestApi
{
    public async Task FunA(int x)
    {
        await Task.Delay(500);
        Console.WriteLine("Task await 500ms");
    }

    public async Task FunB(int x, string y)
    {
        await Task.Delay(600);
        Console.WriteLine("Task await 600ms");
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private async Task Wrapper(Func<Task> next)
    {
        Console.WriteLine("Hello");
        await next();
        Console.WriteLine("World");
    }
}

Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1)
//Output:
// Hello
// Task await 500ms
// World

api.FunB(1, "SJC")
//Output:
// Hello
// Task await 600ms
// World

Wrapper for Task method:

• Having [Wrapper] attribute
• Signature: async Task Wrapper(Func<Task> next)

2.3 Task<TResult> method

public interface ITestApi
{
    Task<int> FunA(int x);
    Task<string> FunB(int x, string y);
}

public class ApiClient : ITestApi
{
    public async Task<int> FunA(int x)
    {
        await Task.Delay(100);
        Console.WriteLine("Task await 100ms");
        return x;
    }

    public async Task<string> FunB(int x, string y)
    {
        await Task.Delay(200);
        Console.WriteLine("Task await 200ms");
        return x + y;
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private async Task<T> Wrapper<T>(Func<Task<T>> next)
    {
        Console.WriteLine("Hello");
        var r = await next();
        Console.WriteLine("World");
        return r;
    }
}

Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1)
//Output:
// Hello
// Task await 100ms
// World

api.FunB(1, "SJC")
//Output:
// Hello
// Task await 200ms
// World

Wrapper method:

• Having [Wrapper] attribute
• Signature: async Task<T> Wrapper<T>(Func<Task<T>> next)
• The wrapper's return type Task<> must be convertible to wrapped's return type Task<> (in this case, the generic type Task<T> is convertible to Task<int> or Task<string>)
• The wrapper must have a Func<> parameter

3. Wrapper parameters

3.1 Single param

public interface ITestApi
{
    int FunA(int role);
    string FunB(int role, string y);
}

public class ApiClient : ITestApi
{
    public int FunA(int role)
    {
        Console.WriteLine(role);
        return role;
    }

    public string FunB(int role, string y)
    {
        Console.WriteLine($"{role} {y}");
        return $"{role} {y}";
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper<T>(int role, Func<int, T> next)
    {
        Console.WriteLine("Hello");
        var r = next(role);
        Console.WriteLine("World");
        return r;
    }
}

Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1)
//Output:
// Hello
// 1
// World

api.FunB(1, "SJC")
//Output:
// Hello
// 1 SJC
// World

Wrapper method:

• Having [Wrapper] attribute
• Signature: T Wrapper<T>(int role, Func<int, T> next)
  • All parameters before the last param (Func<int, T> next) must be match exactly within parameters of each interface methods. If not, default implementation is used. E.g. int userRole or double role will not be match.
  • Last param signature Func<int, T> next).
  • Param type in last param Func is int must match with int role

3.2 Too many param

public interface ITestApi
{
    int FunA(int role);
    string FunB(int role, string y);
}

public class ApiClient : ITestApi
{
    public int FunA(int role)
    {
        Console.WriteLine(role);
        return role;
    }

    public string FunB(int role, string y)
    {
        Console.WriteLine($"{role} {y}");
        return $"{role} {y}";
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper<T>(int role, string name, Func<int, string, T> next)
    {
        Console.WriteLine("Hello");
        var r = next(role, name);
        Console.WriteLine("World");
        return r;
    }
}

It will generate the interface implementation using default not using wrapper. Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1)
//Output:
// 1

api.FunB(1, "SJC")
//Output:
// 1 SJC

Wrapper method:

• string name param in wrapper method match NO param in all interface methods.

3.3 Wrapper parameters resolution

3.3.1 More params - higher precedence

public interface ITestApi
{
    int FunA(int role, string name);
}

public class ApiClient : ITestApi
{
    public int FunA(int role, string name)
    {
        Console.WriteLine($"{role}");
        return role;
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper1<T>(int role, Func<int, T> next)
    {
        Console.WriteLine("Wrapper1");
        var r = next(role);
        return r;
    }

    [Wrapper]
    private T Wrapper2<T>(int role, string name, Func<int, string, T> next)
    {
        Console.WriteLine("Wrapper2");
        var r = next(role, name);
        return r;
    }
}

It will generate the interface implementation.

• Wrapper2 → FunA
• Wrapper2 is higher precedence than Wrapper1 because it covers more aspect (params) of FunA than Wrapper1 Using

TestApi api = new TestApi(new ApiClient());

api.FunA(1, "SJC")
//Output:
// Wrapper2
// 1

3.3.2 Equal params - compile error

public interface ITestApi
{
    int FunA(int role, string name, DateTime dob, decimal amount);
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper1<T>(int role, string name, Func<int, string, T> next)
    {
        // If role is VIP then call manager for permission
        var r = next(role, name);
        // More logging code here...
        return r;
    }

    [Wrapper]
    private T Wrapper2<T>(int role, DateTime dob, Func<int, DateTime, T> next)
    {
        // If role is VIP then call manager for permission
        var r = next(role, dob);
        // More logging code here...
        return r;
    }
}

It will raises two compiler errors:

IFI1002 Wrapper method FunA matches Wrapper1

IFI1002 Wrapper method FunA matches Wrapper2

because both Wrapper1 and Wrapper2 cover equally 2 params of FunA

4. Wrapper return

4.1 Convertible types

The following concrete types are convertible to other generic type or equal to itself:

• int is convertible to int (equally)

• int is convertible to generic T

• IEnumerable<int> is convertible to generic T

• IEnumerable<int> is convertible to generic IEnumerable<T>

• IEnumerable<int> is convertible to generic IEnumerable<int> (equally)

• IEnumerable<IDictionary<int, string>> is convertible to generic T

• IEnumerable<IDictionary<int, string>> is convertible to generic IEnumerable<T>

• IEnumerable<IDictionary<int, string>> is convertible to generic IEnumerable<IDictionary<TKey, TValue>>

• IEnumerable<IDictionary<int, string>> is convertible to generic IEnumerable<IDictionary<int, TValue>>

• IEnumerable<IDictionary<int, string>> is convertible to generic IEnumerable<IDictionary<TKey, string>>

• IEnumerable<IDictionary<int, int>> is convertible to generic IEnumerable<IDictionary<T, T>>

• IEnumerable<IDictionary<int, int>> is convertible to generic IEnumerable<IDictionary<TKey, TValue>>

Note: the following types are NOT convertible

• IEnumerable<int> is NOT convertible to generic IEnumerable<decimal>
• IEnumerable<IDictionary<int, string>> is NOT convertible to generic IEnumerable<IDictionary<T, T>>

4.2 Wrapper return type resolution

4.2.1 Exactly match (Type Equal)

public interface ITest
{
    int Func(int arg1);
}

public class ApiClient : ITest
{
    public int Func(int arg1)
    {
        Console.WriteLine(arg1);
        return arg1;
    }
}
public partial class Test : ITest
{
    [InterfaceFiller]
    private ITest test1;

    public Test(ITest test1)
    {
        this.test1 = test1;
    }

    [Wrapper]
    private int Wrapper1(Func<int> next)
    {
        Console.WriteLine("Wrapper1");
        return next();
    }

    [Wrapper]
    private T Wrapper2<T>(Func<T> next)
    {
        Console.WriteLine("Wrapper2");
        return next();
    }
}

It will generate implementation using Wrapper1 because it has exactly match (equal) return type int with method ITest.Func

Using

TestApi api = new TestApi(new ApiClient());

api.Func(1)
//Output:
// Wrapper1
// 1

4.2.2 Less generic parameter type

public interface ITest
{
    IDictionary<int, decimal> Func(int arg1);
}

public class ApiClient : ITest
{
    public IDictionary<int, decimal> Func(int arg1)
    {
        Console.WriteLine(arg1);
        return default;
    }
}

public partial class Test : ITest
{
    [InterfaceFiller]
    private ITest test1;

    public Test(ITest test1)
    {
        this.test1 = test1;
    }

    [Wrapper]
    private IDictionary<TKey, TValue> Wrapper1<TKey, TValue>(Func<IDictionary<TKey, TValue>> next)
    {
        Console.WriteLine("Wrapper1");
        return next();
    }

    [Wrapper]
    private IDictionary<int, TValue> Wrapper2<TValue>(Func<IDictionary<int, TValue>> next)
    {
        Console.WriteLine("Wrapper2");
        return next();
    }
}

It will generate implementation using Wrapper2 because it has less generic parameter type (TValue) than Wrapper1 (TKey, TValue)

Using

TestApi api = new TestApi(new ApiClient());

api.Func(1)
//Output:
// Wrapper2
// 1

4.2.2 Less generic parameter type (2)

public interface ITest
{
    IDictionary<int, int> Func(int arg1);
}
public class ApiClient : ITest
{
    public IDictionary<int, int> Func(int arg1)
    {
        Console.WriteLine(arg1);
        return default;
    }
}
public partial class Test : ITest
{
    [InterfaceFiller]
    private ITest test1;

    public Test(ITest test1)
    {
        this.test1 = test1;
    }

    [Wrapper]
    private IDictionary<TKey, TValue> Wrapper1<TKey, TValue>(Func<IDictionary<TKey, TValue>> next)
    {
        Console.WriteLine("Wrapper1");
        return next();
    }

    [Wrapper]
    private IDictionary<T, T> Wrapper2<T>(Func<IDictionary<T, T>> next)
    {
        Console.WriteLine("Wrapper2");
        return next();
    }
}

It will generate implementation using Wrapper2 because it has less generic parameter type (T) than Wrapper1 (TKey, TValue)

Using

TestApi api = new TestApi(new ApiClient());

api.Func(1)
//Output:
// Wrapper2
// 1

4.2.3 More generic level

public interface ITest
{
    IEnumerable<int> Func(int arg1);
}

public class ApiClient : ITest
{
    public IEnumerable<int> Func(int arg1)
    {
        Console.WriteLine(arg1);
        return default;
    }
}

public partial class Test : ITest
{
    [InterfaceFiller]
    private ITest test1;

    public Test(ITest test1)
    {
        this.test1 = test1;
    }

    [Wrapper]
    private T Wrapper1<T>(Func<T> next)
    {
        Console.WriteLine("Wrapper1");
        return next();
    }

    [Wrapper]
    private IEnumerable<T> Wrapper2<T>(Func<IEnumerable<T>> next)
    {
        Console.WriteLine("Wrapper2");
        return next();
    }
}

It will generate implementation using Wrapper2 because it has more generic level return type IEnumerable<T> than T in Wrapper1

Using

TestApi api = new TestApi(new ApiClient());

api.Func(1)
//Output:
// Wrapper2
// 1

4.2.4 More generic level (win over less generic param)

public interface ITest
{
    IDictionary<int, IEnumerable<decimal>> Func(int arg1);
}

public class ApiClient : ITest
{
    public IDictionary<int, IEnumerable<decimal>> Func(int arg1)
    {
        Console.WriteLine(arg1);
        return default;
    }
}

public partial class Test : ITest
{
    [InterfaceFiller]
    private ITest test1;

    public Test(ITest test1)
    {
        this.test1 = test1;
    }

    [Wrapper]
    private IDictionary<int, T> Wrapper1<T>(Func<IDictionary<int, T>> next)
    {
        Console.WriteLine("Wrapper1");
        return next();
    }

    [Wrapper]
    private IDictionary<T, IEnumerable<T1>> Wrapper2<T, T1>(Func<IDictionary<T, IEnumerable<T1>>> next)
    {
        Console.WriteLine("Wrapper2");
        return next();
    }
}

It will generate implementation using Wrapper2 because it has more generic level return type IDictionary<IEnumerable<>> than IDictionary<> in Wrapper1

Using

TestApi api = new TestApi(new ApiClient());

api.Func(1)
//Output:
// Wrapper2
// 1

6. Wrapper (with parameter) for Task method

Signature: async Task Wrapper(int a, Func<int, Task> next)

7. Wrapper (with parameter) for Task<TResult> method

Signature: async Task<T> Wrapper<T>(int a, Func<int, Task<T>> next)

8. C# Caller Attributes

Support C# built-in caller attributes

Wrapper resolution note: if two wrapper methods cover equally on param then which has more caller params will win.

public interface ITestApi
{
    int FunA(int role, string name, DateTime dob, decimal amount);
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper1<T>(int role, string name, Func<int, string, T> next, [CallerMemberName] string memberName = "", [CallerLineNumber] int line = 0, [CallerArgumentExpression("next")] string exp = "", [CallerFilePath] string sourceFilePath = "")
    {
        // If role is VIP then call manager for permission
        var r = next(role, name);
        // More logging code here...
        return r;
    }
}

9. CallerParamByName and CallerParamByIndex attributes

• Apply attribute [CallerParamByName("paramName")] or [CallerParamByIndex(1,true)] to wrapper method param to match with interface method param
  • [CallerParamByName("paramName")] will match by paramName
  • [CallerParamByIndex(1,true)] will match by applying index value to interface method param list
• The wrapper method param must have default value
• If no matching then default value is used
• The type of interface param and the type of wrapper param:
  • Equals then interface param is passed to wrapper param
  • Convertible then interface param is converted and passed to wrapper param
  • Not convertible then default value is used

Note: Should NOT update/modify the value matched param. It causes side effect if it is reference object.

public class EncrytionArth
{
    public string Pseed;
}
public class S15 : EncrytionArth
{
    public string Title;
}

public interface ITestApi
{
    int FunA(int idm, EncrytionArth strat, string name, DateTime dob, decimal amount);
    int FunB(S15 strat, string hasCode);
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller]
    private ITestApi testApi;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
    }

    [Wrapper]
    private T Wrapper1<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        // this will match both FunA and FunB
        Log.Info(arth.Pseed);

        var r = next();
        // More logging code here...
        return r;
    }
}

10 Wrapper resolution in summary

1. Has more parameters
2. Then return type
3. Then more caller parameters

NOTE: All wrapper methods name should NOT be the same in the class.

11. Reuse your Wrapper logic

• Move your Wrapper methods to other class.
• Decorate it's methods with [Wrapper] attribute and make them public.
• Create the instance of it in the using class
• Add the variable name to [InterfaceFiller]

public interface ITestApi
{
    int FunA(int idm, EncrytionArth strat, string name, DateTime dob, decimal amount);
    int FunB(S15 strat, string hasCode);
}

public class WrapperLogic
{
    [Wrapper]
    public T Wrapper1<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("WrapperLogic");

        return next();
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller(nameof(wrapperLogic))]
    private ITestApi testApi;

    private WrapperLogic wrapperLogic;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
        wrapperLogic = new WrapperLogic();
    }
}

10.1 Combine a wrapper object with class own wrapper methods

public interface ITestApi
{
    int FunA(int idm, EncrytionArth strat, string name, DateTime dob, decimal amount);
    int FunB(S15 strat, string hasCode);
}

public class WrapperLogic
{
    [Wrapper]
    public T Wrapper1<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("WrapperLogic message");

        return next();
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller(nameof(wrapperLogic))]
    private ITestApi testApi;

    private WrapperLogic wrapperLogic;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
        wrapperLogic = new WrapperLogic();
    }

    [Wrapper]
    public T Wrapper1<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("Own class begin");
        var v = next();
        return v;

    }
}

• The calling order: WrapperLogic object → class own wrapper methods
• Log result is:
  • WrapperLogic message
  • Own class wrapper

10.2 Combine multiple wrapper objects with class own wrapper methods

public interface ITestApi
{
    int FunA(int idm, EncrytionArth strat, string name, DateTime dob, decimal amount);
    int FunB(S15 strat, string hasCode);
}

public class WrapperLogging
{
    [Wrapper]
    public T Wrapper<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("WrapperLogging begin");
        var v = next();
        Log.Info("WrapperLogging end");
        return v;
    }
}

public class WrapperTiming
{
    [Wrapper]
    public T Wrapper<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("WrapperTiming begin");
        var v = next();
        Log.Info("WrapperTiming end");
        return v;
    }
}

public partial class TestApi : ITestApi
{
    [InterfaceFiller(nameof(wrapperLogging), nameof(wrapperTiming))]
    private ITestApi testApi;

    private WrapperLogging wrapperLogging;
    private WrapperTiming wrapperTiming;

    public TestApi(ITestApi testApi)
    {
        this.testApi = testApi;
        wrapperLogging = new WrapperLogging();
        wrapperTiming = new WrapperTiming();

    }

    [Wrapper]
    public T Wrapper<T>(Func<T> next, [CallerParamByName("strat")] EncrytionArth arth = default)
    {
        Log.Info("Own class wrapper");

        return next();
    }
}

• The calling order (right to left): WrapperTiming → WrapperLogging → class own wrapper methods
• Log result is:
  • WrapperTiming begin
    • WrapperLogging begin
      • Own class wrapper
    • WrapperLogging end
  • WrapperTiming end

Void method

Void (Unsupported)

Issue Report

https://github.com/ghostnguyen/InterfaceFillerIssue/issues