Command-line apps (Nullean.Argh)

Shell 
dotnet add package Nullean.Entities.Argh

For a Nullean.Argh command, register the constraints for its option type, and a violation fails the way Argh's own checks do:

C# 
ArghConstraints.Register<ServeOptions>();

app.Map("serve", ([AsParameters("serve")] ServeOptions options) => ...);
// $ app serve --serve-port 70000
// Error: --serve-port: must be between 1 and 65535        (then the flag's help rows and the usage line; exit code 2, handler not run)
  1. before RunAsync; or Register(ServeRules.All) for a companion's set

It works through Argh's ArghValidation hook, so it covers [AsParameters] objects, global and namespace options, and TryParseArgh in tests. Constraints run right after Argh's own checks ([Range], [Existing] and so on), and the error names the flag from Violation.Member.

The package builds on Nullean.Entities and Nullean.Argh.Interfaces, needs Nullean.Argh 0.28, uses no reflection, and is trim and NativeAOT clean. The package README has a complete program, with the registration in a module initializer.