Completion provider should be able to detect caller is help usage doc

[AArnott]

When using the AddCompletions method to add runtime-determined completions for an argument, I don't want those completions to appear in the help doc. This is usually because the completion options are so many, the usage doc just gets long with options that don't need to be enumerated there.

An example of how wordy it can be is even demonstrated in the published docs.

There appears to be no exposed property to detect that my callback is invoked merely to print the usage doc.
Can a property be added to CompletionContext to indicate whether it's for help docs or actual completions?
Or just allow a property to turn off completions being used to replace an argument name in the usage doc.

[AArnott]

My workaround for now is this:

// Skip completions when used in the presentation in the -? usage doc.
// Per https://github.com/dotnet/command-line-api/issues/2185, we cannot tell when we're in that context,
// so guess based on no tokens.
if (context.ParseResult.Tokens.Count == 0)
{
    yield break;
}

[KalleOlaviNiemitalo]

Or just allow a property to turn off completions being used to replace an argument name in the usage doc.

Can't you do that already by setting HelpName? #1976

[AArnott]

Yes, that works. Just not particularly discoverable. Thanks.