Cannot use more than 8 options on one command

[winterleitner]

I just stumbled across this weird behaviour.

This will compile.

var stringOption = new Option<string?>(name: "--test", description: "Test Option",
    getDefaultValue: () => null);

var cmd = new Command("testcommand", "This has 7 arguments");
cmd.SetHandler(async (a, b, c, d, e, f, g, h) => {}, 
    stringOption, stringOption, stringOption, stringOption, stringOption,
    stringOption, stringOption, stringOption);

while this won't.

var stringOption = new Option<string?>(name: "--test", description: "Test Option",
    getDefaultValue: () => null);

var cmd = new Command("testcommand", "Tests more than 7 arguments, this example has 8");
cmd.SetHandler(async (a, b, c, d, e, f, g, h, i) => {}, 
    stringOption, stringOption, stringOption, stringOption, stringOption,
    stringOption, stringOption, stringOption, stringOption);

All I did change here was add one more parameter. According to the docs, there should be overloads for up to 16 parameters.

Any ideas what is going on?

Edit

Looking into the Handler.Func.cs source file (partial class), there are actually only implementations up to 8 generic parameters. Unfortunately, the AnonymousCommandHandler class used in the methods is internal, so it cannot easily be extended.

[KalleOlaviNiemitalo]

The change was announced in #1750 (comment):

Finally, we've reduced the number of SetHandler overloads. Where before there were overloads supporting up to sixteen generic parameters, they now only go up to eight.

I don't know why the API documentation still hasn't been updated.

[elgonzo]

FYI: The general documentation / usage guide for System.CommandLine mentions both 16 parameters and 8 parameters for handlers on the same page:

• https://learn.microsoft.com/en-us/dotnet/standard/commandline/model-binding#parameter-binding-up-to-16-options-and-arguments
• https://learn.microsoft.com/en-us/dotnet/standard/commandline/model-binding#parameter-binding-more-than-8-options-and-arguments