Source Generator to create an Interface from a class definition
$ dotnet add package AutomaticInterfaceA C# Source Generator to automatically create Interface from classes.
Not all .NET Interfaces are created equal. Some Interfaces are lovingly handcrafted, e.g. the public interface of your .NET package which is used by your customers. Other interfaces are far from lovingly crafted, they are birthed because you need an interface for testing or for the DI container. They are often implemented only once or twice: The class itself and a mock for testing. They are noise at best and often create lots of friction. Adding a new method / field? You have to edit the interface, too!. Change parameters? Edit the interface. Add documentation? Hopefully you add it to the interface, too!
This Source Generator aims to eliminate this cost by generating an interface from the class, without you needing to do anything. This interface will be generated on each subsequent build, eliminating the the friction.
using AutomaticInterfaceAttribute;
using System;
namespace AutomaticInterfaceExample
{
/// <summary>
/// Class Documentation will be copied
/// </summary>
[GenerateAutomaticInterface] // you need to create an Attribute with exactly this name in your solution. You cannot reference Code from the Analyzer.
class DemoClass: IDemoClass // You Interface will get the Name I+classname, here IDemoclass.
// Generics, including constraints are allowed, too. E.g. MyClass<T> where T: class
{
/// <summary>
/// Property Documentation will be copied
/// </summary>
public string Hello { get; set; } // included, get and set are copied to the interface when public
public string OnlyGet { get; } // included, get and set are copied to the interface when public
/// <summary>
/// Method Documentation will be copied
/// </summary>
public string AMethod(string x, string y) // included
{
return BMethod(x,y);
}
private string BMethod(string x, string y) // ignored because not public
{
return x + y;
}
public string CMethod<T, T1, T2, T3, T4>(string? x, string y) // included
where T : class
where T1 : struct
where T3 : DemoClass
where T4 : IDemoClass
{
return "Ok";
}
public static string StaticProperty => "abc"; // static property, ignored
public static string StaticMethod() // static method, ignored
{
return "static" + DateTime.Now;
}
/// <summary>
/// event Documentation will be copied
/// </summary>
public event EventHandler ShapeChanged; // included
private event EventHandler ShapeChanged2; // ignored because not public
private readonly int[] arr = new int[100];
public int this[int index] // currently ignored
{
get => arr[index];
set => arr[index] = value;
}
}
}
This will create this interface:
#nullable enable
using System.CodeDom.Compiler;
using AutomaticInterfaceAttribute;
using System;
/// <summary>
/// Result of the generator
/// </summary>
namespace AutomaticInterfaceExample
{
/// <summary>
/// Bla bla
/// </summary>
[GeneratedCode("AutomaticInterface", "")]
public partial interface IDemoClass
{
/// <summary>
/// Property Documentation will be copied
/// </summary>
string Hello { get; set; }
string OnlyGet { get; }
/// <summary>
/// Method Documentation will be copied
/// </summary>
string AMethod(string x, string y);
string CMethod<T, T1, T2, T3, T4>(string? x, string y) where T : class where T1 : struct where T3 : DemoClass where T4 : IDemoClass;
/// <summary>
/// event Documentation will be copied
/// </summary>
event System.EventHandler ShapeChanged;
}
}
#nullable restoredotnet add package AutomaticInterface[GenerateAutomaticInterface]. You can just copy the minimal code from this Repo (see the AutomaticInterfaceAttribute project). It's the easiest way to get that attribute because you cannot reference any code from the analyzer package.SomeClass: ISomeClassAny errors? Ping me at: christiian.sauer@codecentric.de
Newer Visual Studio Versions (2019+) can see the source code directly:
Alternatively, the Source Generator generates a log file - look out for a "logs" folder somewhere in bin/debug/... OR your temp folder /logs. The exact location is also reported on Diagnosticlevel Info.
Please ping me via Github. Ideally create a Test for your problem - source generators are a pain to debug and tests solve that problem.
Thanks to dnf for creating some great extensions. I use them partially in this Generator. Unfortunately due to problems referencing packages I cannot depend on his packages directly.
Should be simply a build and run Tests
void test(string x = null) should now work.