Should `configopaque.String` implement `encoding.BinaryMarshaler`?

[mx-psi]

It would be easy to do (e.g. here is the implementation for net.URL, ours would just be returning []bytes(maskedString), nil).

Any reason not to do it?

[bogdandrutu]

I don't have a reason to not to, but I do not have a reason on why to. So my rule of thumb when in doubt leave it out :)

[TylerHelmuth]

If this statement is true, then I do think we'd want to prevent this situation. If the goal of configopaque.String is to hide the value unless the user explicitly decides they want to see it, then I think the roundabout situation of configopaque -> []byte -> string is a leak.

[TylerHelmuth]

If we chose to do this: #9279

[mx-psi]

I don't have a reason to not to, but I do not have a reason on why to. So my rule of thumb when in doubt leave it out :)

Two arguments in favor:

• Implementing this interface later may be breaking for users, so we may as well do it now
• What Tyler said on Should configopaque.String implement encoding.BinaryMarshaler? #9272 (comment): if the goal is to prevent leaking other than by casting to string then this would prevent leakage.