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Providers

What a provider is

A provider is a pluggable rule for satisfying a value that isn't covered by an explicit registration or rule — the mechanism Compono.NSubstitute and Compono.Bogus use to add their behavior without the core Compono package knowing either of them exists. A provider implements one method:

public interface ICompositionValueProvider
{
    CompositionProviderResult TryProvide(in CompositionProviderRequest request, ICompositionContext context);
}

It returns CompositionProviderResult.NotHandled for anything it doesn't apply to, or CompositionProviderResult.Handled(value) for a value it produces — it's a "maybe I can help with this one" rule, not a required handler for every type.

The two built-in providers

  • Compono.Bogus's BogusMemberNameProvider matches string-typed members by exact name against a known convention list (FirstName, Email, and similar), producing a deterministically-seeded, semantically realistic value instead of an arbitrary one.
  • Compono.NSubstitute's NSubstituteProvider matches any interface or delegate type (and, optionally, unsealed abstract classes), producing a configured Substitute.For(...) instead of requiring a hand-written fake implementation.

Neither is wired in by default — UseBogus()/UseNSubstitute() add them to the pipeline explicitly, which is also why the core Compono package has zero dependency on either Bogus or NSubstitute.

Why two provider stages

Compono.Bogus's convention matching and Compono.NSubstitute's substitute creation don't compete for the same values (a string member and an interface dependency are never the same request), but they run as two logically distinct stages precisely so that ordering between UseBogus()/UseNSubstitute() calls never matters — a provider only influences the stage it's registered into. The exact stage order relative to registrations, rules, and generated default construction is Architecture's concern, not this page's — what matters here is that a provider is always a fallback, tried only once nothing more specific (an exact registration, a type/member rule) already claimed the value.

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