Zomp.MethodCloning.Variants

Zomp.MethodCloning.Variants

Write a method once. Get one per format, type or mode.

A source generator that replaces T4 templates. Write SaveAsBmp by hand, list the other formats, and SaveAsGif, SaveAsPng and the rest are generated on every build, in any IDE.

You write

[CloneVariants("Bmp", "Gif", "Png")]
public static partial class ImageExtensions
{
    /// <summary>Saves the image in the Bmp format.</summary>
    public static void SaveAsBmp(this Image image, Stream stream, BmpEncoder? encoder)
        => image.Save(stream, encoder ?? BmpFormat.Instance.DefaultEncoder);
}

You get

/// <summary>Saves the image in the Gif format.</summary>
public static void SaveAsGif(this Image image, Stream stream, GifEncoder? encoder)
    => image.Save(stream, encoder ?? GifFormat.Instance.DefaultEncoder);

/// <summary>Saves the image in the Png format.</summary>
public static void SaveAsPng(this Image image, Stream stream, PngEncoder? encoder)
    => image.Save(stream, encoder ?? PngFormat.Instance.DefaultEncoder);

Simplified for reading: the generated code fully qualifies every name.

Install

<PackageReference Include="Zomp.MethodCloning.Variants" PrivateAssets="all" />

Works with the .NET 8 SDK or later. Nothing is added to your assembly.

What gets swapped

Where	Bmp becomes Gif
The method's name	SaveAsBmp to SaveAsGif (the name must contain the word)
Types it uses	Formats.Bmp.BmpEncoder to Formats.Gif.GifEncoder
Static calls by simple name	SaveAsBmp(image, stream) to SaveAsGif(image, stream)
Its documentation	"in the Bmp format" to "in the Gif format"
The file's using directives	using Formats.Bmp; to using Formats.Gif;

A type with no counterpart, such as a BmpQuantizer with no GifQuantizer, is kept, with warning ZMC003.

Good to know

• On a type, the attribute covers every method in that declaration. On a method, it covers just that method, and wins over the type's.
• Nullability follows your method. Write it in #nullable disable to match what a T4 template produced.
• The word is replaced everywhere. With Normal as the word, Normalize() would become Multiplyize(). Pick a word that appears nowhere else.
• Not swapped: generic and nested types, calls written as image.SaveAsBmp(), string literals, and comments inside the method.
• Not cloned: members of C# 14 extension blocks (ZMC004).

Full rules, limitations and a step-by-step migration from T4: the reference.

Diagnostics

ID	Severity	Means	Fix
ZMC001	Error	Two variants would declare the same member	Remove the duplicate from the list
ZMC002	Error	The method's name lacks the word being swapped	Rename the method, or take the attribute off it
ZMC003	Warning	A type has no counterpart, so it is kept	Add the counterpart, or suppress if intended
ZMC004	Error	The method is in a C# 14 extension block	Write it as a classic extension method