[swift-corelibs-dev] Unavailability macros for APIs that aren't going to be implemented on Linux?
alblue at apple.com
Fri Jul 28 14:30:32 CDT 2017
On 28 Jul 2017, at 19:44, Tony Parker <anthony.parker at apple.com> wrote:
> This sounds like a good plan to me. We’ll have to discuss the specifics of what is marked unavailable this way, probably best via code review.
> I think we had more hope for some of the more-dynamic methods (e.g. NSSortDescriptor, NSExpression), but it does seem clear at this point that the current API is unsuitable for Swift in various ways.
Perhaps if more dynamic introspection lands in a future version of Swift they might make sense. It's also possible that some of the new keypath stuff being added in Swift might make a good potential API in future, so maybe those aren't quite as cut and dry.
In the meantime I'll take a stab next week at proposing some unavailability annotations for some of the stuff which almost certainly doesn't make sense, to do with Mach ports and NSZone.
> - Tony
>> On Jul 28, 2017, at 7:27 AM, Ian Partridge via swift-corelibs-dev <swift-corelibs-dev at swift.org> wrote:
>> Hi Al, thanks for bringing this up.
>> My view is that we shouldn't have API in the project which is never going to be implemented. The contents of swift-corelibs-foundation should represent a baseline of fundamental types and functionality which is useful to all applications and can be implemented on a broad range of platforms and operating systems.
>> I think it is more useful to developers who are porting their Swift applications to other platforms if they are faced with a helpful message when their app attempts to use unavailable API, rather than just "ERROR: type 'NSWhatever' has no member 'foo'" - so I like your idea of using @available annotations to guide people.
>> Once Swift 4 is out of the door, I think we should do a review of the codebase and decide which of the remaining NSUnimplemented() are really NSProbablyNever().
>> This will also help new contributors to swift-corelibs-foundation as they will be able to be confident that every NSUnimplemented() is a genuine opportunity to contribute.
>> Ian Partridge
>>> On 28 July 2017 at 15:07, Alex Blewitt via swift-corelibs-dev <swift-corelibs-dev at swift.org> wrote:
>>> I've pushed a change which will add an unavailability warning for a method which was deprecated at the point of being added to Swift, has never worked, and likely never will:
>>> There are some other types in Foundation which aren't likely to ever be implementable in Swift on Linux; Bundle.unload, NSPort/PortMessage, copy(with zone) etc. The majority of these methods use NSUnimplemented(), which means there are often unannounced runtime errors that you can get from something that compiled correctly.
>>> I'd like to suggest that we attempt to resolve this problem, either by removing the features whihc are never going to be implemented (e.g. by commenting out the calls) or by marking them as @available(*,unavailable, message:"Not available on the Linux platform"). That way, calls that are known cannot work can be identified at compile time instead of at run-time.
>>> I hope we'll then be able to remove the NSUnimplemented calls on the types that can never be implemented, so that we can focus on those types and functions that we can. Alternatively we can define a different macro, say NSUnavailableOnLinux, to indicate that this functionality cannot be present (as opposed to just leaving it blank).
>>> What do you think?
>>> $ git grep -c NSUnimplemented | sort -n -r -k2 -t:
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>>> swift-corelibs-dev at swift.org
>> Ian Partridge
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>> swift-corelibs-dev at swift.org
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