InterfaceFillerCodeGen 1.1.1-alpha

InterfaceFiller - Explicit Aspect Oriented Programming (AOP) in C#

The most simple but full-feature AOP framework in .NET C# by:

• Minimal and concise. All junk code are:
  • Two parameter-less attributes
  • string methodName
• Explicit. No reflection in hell.
• Flexible. wysiwyg

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

Table of content:

• 1. InterfaceFiller attribute
• 2. Wrapper attribute
• 3. Wrapper With Parameter
• 4. Wrapper Resolution
• 5. Wrapper (with parameter) for Task method
• 6. Wrapper (with parameter) for Task<TResult> method
• 7. string methodName
• Void method
• Issue Report

Changelog

[1.1.0] - 2023-08-10

Added

• string methodName

1. [InterfaceFiller] attribute {#InterfaceFiller}

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.

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int x, int y) => testApi.FunA(x, y);

    public System.Threading.Tasks.Task<System.Net.Http.StreamContent> FunB(System.Threading.Barrier barrier, System.Random randomAccess) => testApi.FunB(barrier, randomAccess);
}

Note

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

<a id="Wrapper"></a>

2. Wrapper

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

2.1 Normal method

Given the interface

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

and the class

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

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

    [Wrapper]
    private T Wrapper<T>(Func<T> next)
    {
        // Logging code here...
        var r = next();
        // More logging code here...
        return r;
    }
}

It will generate the interface.

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int x)
    {
        Func<int> func = () => testApi.FunA(x);
        return Wrapper(func);
    }

    public string FunB(int x, string y)
    {
        Func<string> func = () => testApi.FunB(x, y);
        return Wrapper(func);
    }
}

Wrapper method:

• Having [Wrapper] attribute
• Signature: T Wrapper<T>(Func<T> next)
• Must be Generic method
• The generic type must be method generic type

2.2 Task method

Given the interface

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

and the class

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

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

    [Wrapper]
    private async Task Wrapper(Func<Task> next)
    {
        // Logging code here...
        await next();
        // More Logging code here...
    }
}

It will generate the interface implementation using back-up field and wapper method.

// <auto-generated />
partial class TestApi : ITestApi
{
    public async System.Threading.Tasks.Task FunA(int x)
    {
        Func<System.Threading.Tasks.Task> func = () => testApi.FunA(x);
        await Wrapper(func);
    }

    public async System.Threading.Tasks.Task FunB(int x, string y)
    {
        Func<System.Threading.Tasks.Task> func = () => testApi.FunB(x, y);
        await Wrapper(func);
    }
}

Wrapper for Task method:

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

2.3 Task<TResult> method

Given the interface

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

and the class

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)
    {
        // Logging code here...
        var r = await next();
        // More Logging code here...
        return r;
    }
}

It will generate the interface implementation.

// <auto-generated />
partial class TestApi : ITestApi
{
    public async System.Threading.Tasks.Task<int> FunA(int x)
    {
        Func<System.Threading.Tasks.Task<int>> func = () => testApi.FunA(x);
        return await Wrapper(func);
    }

    public async System.Threading.Tasks.Task<string> FunB(int x, string y)
    {
        Func<System.Threading.Tasks.Task<string>> func = () => testApi.FunB(x, y);
        return await Wrapper(func);
    }
}

Wrapper method:

• Having [Wrapper] attribute
• Signature: async Task<T> Wrapper<T>(Func<Task<T>> next)
• Must be Generic method
• The generic type must be method generic type

<a id="WrapperWithParameter"></a>

3. Wrapper (with parameter)

3.1 Single param

Concern your 'Aspect' only.

Given the interface

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

and the class

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)
    {
        // If role is VIP then call manager for permission
        var r = next(role);
        // More logging code here...
        return r;
    }
}

It will generate the interface implementation using back-up field and wapper method.

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role)
    {
        Func<int, int> func = (__role) => testApi.FunA(__role);

        return Wrapper(role, func);
    }

    public string FunB(int role, string y)
    {
        Func<int, string> func = (__role) => testApi.FunB(__role, y);

        return Wrapper(role, func);
    }
}

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).
  • Input in last param int must match with int role
• Must be Generic method
• The generic type must be method generic type

3.2 Too many param

Concern your 'Aspect' only.

Given the interface

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

and the class

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)
    {
        // If role is VIP then call manager for permission
        var r = next(role, name);
        // More logging code here...
        return r;
    }
}

It will generate the interface implementation using default not wrapper.

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role)
        => testApi.FunA(role);

    public string FunB(int role, string y)
        => testApi.FunB(role, y);
}

Wrapper method:

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

<a id="WrapperResolution"></a>

4. Mutiple Wrapper (Wrapper resolution)

4.1 Exactly match

Given the interface

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

and the class

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)
    {
        // If role is VIP then call manager for permission
        var r = next(role);
        // More logging code here...
        return r;
    }

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

It will generate the interface implementation.

• Wrapper1 → FunA
• Wrapper2 → FunB

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role)
    {
        Func<int, int> func = (__role) => testApi.FunA(__role);
        return Wrapper1(role, func);
    }

    public string FunB
        (int role, string y)
    {
        Func<int, string, string> func = (__role, __y) => testApi.FunB(__role, __y);
        return Wrapper2(role, y, func);
    }
}

4.2 More params - higher precedence

Given the interface

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

and the class

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)
    {
        // If role is VIP then call manager for permission
        var r = next(role);
        // More logging code here...
        return r;
    }

    [Wrapper]
    private T Wrapper2<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;
    }
}

It will generate the interface implementation.

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

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role, string name, System.DateTime dob, decimal amount)
    {
        Func<int, string, int> func = (__role, __name) => testApi.FunA(__role, __name, dob, amount);
        return Wrapper2(role, name, func);
    }
}

4.2 Equal params - compile error

Given the interface

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

and the class

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 generate junk text to fail compiler because both Wrapper1 and Wrapper2 cover equally 2 params of FunA

// <auto-generated />
partial class TestApi : ITestApi
{
    mutipleWrapper
//Error: WrapperDoc.ITest.FunA(int, string, System.DateTime, decimal) has mutiple wrapper: WrapperDoc.Test.Wrapper1<T>(int, string, System.Func<int, string, T>), WrapperDoc.Test.Wrapper2<T>(int, System.DateTime, System.Func<int, System.DateTime, T>)
}

<a id="WrapperTask"></a>

5. Wrapper (with parameter) for Task method

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

<a id="WrapperTaskTResult"></a>

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

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

<a id="MethodName"></a>

7. string methodName

Add string methodName parameter after Func next to access the caller method name.

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, string methodName)
    {
        // If role is VIP then call manager for permission
        var r = next(role, name);
        // More logging code here...
        return r;
    }
}

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role, string name, System.DateTime dob, decimal amount)
    {
        Func<int, string, int> func = (__role, __name) => testApi.FunA(__role, __name, dob, amount);
        return Wrapper1(role, name, func, "FunA");
    }
}

7.1 Wrapper resolution:

• string methodName has lower precedence than method param

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

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

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role, string name, System.DateTime dob, decimal amount)
    {
        Func<int, int> func = (__role) => testApi.FunA(__role, name, dob, amount);
        return Wrapper1(role, func, "FunA");
    }
}

• string methodName wrapper is selected if method params precedence are equal.

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

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

// <auto-generated />
partial class TestApi : ITestApi
{
    public int FunA(int role, string name, System.DateTime dob, decimal amount)
    {
        Func<int, int> func = (__name) => testApi.FunA(role, __name, dob, amount);
        return Wrapper2(name, func, "FunA");
    }
}

<a id="Void"></a>

Void method

Void (Unsupport)

<a id="Issue"></a>

Issue Report

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