Suggestion for Best Practice RE Default Values and structs

[TonyValenti]

Hi All,
I wanted to mention something I see as not-ideal in a lot of libraries and then provide my solution.
The goal being that code is more clear and has less magic values in it.

As an example, consider this API:

public  ValueTask<RateLimitLease> AcquireAsync(int permitCount = 1, CancellationToken cancellationToken = default);

If I want to call this with the default value for permitCount with no cancellation token, I can just do this:

using var lease = await AcquireAsync();

but if I want to provide a token, then I have to re-specify the default value for ```permitCount``:

using var lease = await AcquireAsync(1, token);

This is not ideal because then in a code review, I'm left wondering if 1 is something the developer picked or if it is a default that is just being respecified.

It would be nice if I could simply do this:

using var lease = await AcquireAsync(default, token);

as it would logically make sense that I am calling the method with the default value of the parameter, however, per C# rules, that actually means "default value of the type" which is 0 and not what I want.

To get around this, in my own APIs I do something like this:

private const int DefaultPermitCount = 1;
public  ValueTask<RateLimitLease> AcquireAsync(int? permitCount = DefaultPermitCount, CancellationToken cancellationToken = default){
  var actualPermitCount = permitCount ?? DefaultPermitCount;
  ...
}

This allows me to cleanly use default to represent the default value for the parameter.

Anyways, It would be nice if core APIs did something like this as well.

[vitek-karas]

Why don't you call it with named parameters?

using var lease = await AcquireAsync(cancellationToken: token);