A simple source generator that creates interfaces by implementations. Useful for when you need an interface purely for the sake of mocking, or maybe you're not sure if you'll need the abstraction later on.

Inspired by net_automatic_interface

Example user implementation:

[GenerateAutoInterface]
public class SampleService : ISampleService
{
    public double Multiply(double x, double y)
    {
        return x * y;            
    }

    public int NiceNumber => 69;
}

Auto generated interface:

public partial interface ISampleService
{
    double Multiply(double x, double y);
    int NiceNumber { get; }
}

Supports:

Methods, properties, indexers.
Default arguments, params arguments.
Generic types and methods.
XML docs.
Explicit interface names (using the Name property on GenerateAutoInterface).
Explicit interface visibility (using the VisibilityModifier property on GenerateAutoInterface).
Explicitly excluding a member from the interface (using [AutoInterfaceIgnore]).

Missing:

Events.
Nested types.
Probably a bunch of edge cases I forgot about.