Em qui., 13 de mai. de 2021 às 13:36, Alan Snyder <javali...@cbfiddle.com> escreveu:
> >> Is this a common practice? Doesn’t it point to a deficiency in the > library API? > > > > Not necessarily. For example, say you want to give access to a particular > > resource (a log stream, say) to trusted callees. Nobody AFAIK passes a > log > > stream as an explicit argument through business logic because that's just > > too much clutter. > > > > That sounds interesting, but I’m not following how scope locals would be > used to solve this problem. > It appears to me that, in this context, scoped locals is inserting itself inside a hierarchy of "overrides". We already have mechanisms which provide "context" capable of carrying "overrides", such as process environment variables and JVM system properties. Those are too global for certain uses such as "overriding" a single method call. So, in a great hierarchy of "overrides", we would have, from the largest to the smallest: process environment variables > JVM system properties > *scoped locals* > method call parameters. Things like these are recurrent in the design of "I/O cancelability", where people are always discovering the need for things like "timeout scopes". It could be argued that "cancelable" APIs must have some "cancellation token " parameter. But there are cases where some domain interface, which was never designed with this in mind, must be implemented over network protocols. This is the case when you must implement a KeyStore or a Cipher with remotely managed private keys. Since you cannot alter KeyStore to pass a "cancellation token" to single methods, you must insert the token as a sort of "override" thing in some parallel storage. -- Pedro Lamarão https://www.prodist.com.br Securing Critical Systems Tel: +55 11 4380-6585 Antes de imprimir esta mensagem e seus anexos, certifique-se que seja realmente necessário. Proteger o meio ambiente é nosso dever. Before printing this e-mail or attachments, be sure it is necessary. It is in our hands to protect the environment.
