[swift-evolution] [Further Discussion] Naming Attributes

[Erica Sadun]

> On Feb 19, 2016, at 2:04 PM, Joe Groff <jgroff at apple.com> wrote:
> 
> 
>> On Feb 19, 2016, at 12:17 PM, Erica Sadun <erica at ericasadun.com <mailto:erica at ericasadun.com>> wrote:
>> 
>> > Here's a problem
>> 
>> * There are Swift attributes: @autoclosure, @available, @objc, @noescape, @nonobjc, @noreturn, @testable, @warn-unused-result, @convention, @noreturn.
>> * There are ObjC-ish/Xcode-ish attributes: @UIApplicationMain, @NSManaged, @NSCopying, @NSApplicationMain, @IBAction, @IBDesignable, @IBInspectable, @IBOutlet
>> * There may be user-definable attributes under SE-0030: for example @lazy, @delayed; these are certainly attribute-ish, and it makes sense to present these using attribute-syntax.
>> * The attribute syntax using `@` has had an intention "to open the space up to user attributes at some point"
>> 
>> > Namespacing
>> 
>> If Swift were to start accepting user-defined attributes,  it would need some way to differentiate and namespace potential conflicts. The most obvious solution looks like this:
>> 
>> `@Swift.autoclosure`, `@UIKit.UIApplicationMain`, `@UIKit.IBOutlet`, `@Swift.noreturn`, `@Custom.lazy`, etc.
>> 
>> Cumbersome, ugly, problematic.
>> 
>> > Modernization
>> 
>> In my initial discussion for modernizing Swift attributes (https://gist.github.com/erica/29c1a7fb7f49324d572f <https://gist.github.com/erica/29c1a7fb7f49324d572f>), I wanted to eliminate snakecase from @warn-unused-result and `mutable_variant`. Of these, the second is a no-brainer. Instead of the non-standard argument label `mutable_variant`, use `mutableVariant`. Problem solved.
>> 
>> Converting `warn-unused-result` to the current standard of lowercase `warnunusedresult` produces a hard-to-read outcome. So in my write-up, I proposed the following amendments:
>> 
>> @Autoclosure // was @autoclosure
>> @Available // was @available
>> @ObjC // was @objc
>> @NoEscape // was @noescape
>> @NonObjC // was @nonobjc
>> @NoReturn // was @noreturn
>> @Testable // was @testable
>> @WarnUnusedResult // was @warn-unused-result
>> @Convention  // was @convention
>> @NoReturn // was @noreturn
>> 
>> This was greeted somewhere between warmly and Siberian Winter depending on respondent. 
>> 
>> > Possible Approaches
>> 
>> After reading through Joe Groff's update to SE-0030, I'd like to push this again in a broader context (which is why I'm starting a new email thread). 
>> 
>> * Is traditional namespacing the way to go? 
>> * Could a simpler solution to upper camel all system-supplied attributes and lower camel all custom attributes be sufficient?
>> * Could any other "custom" decoration differentiate the two with easy parsing: for example @@lazy, @@delayed for custom and single-@ tokens for system supplied?
>> * Should I simply back off on modernizing warn-unused-result until SE-0030 is resolved?
>> 
>> What are your thoughts?
> 
> Once we open the floodgates for user-defined attributes, I think traditional namespacing and name lookup makes a lot of sense. We could conceptually namespace the existing hardcoded attributes into appropriate modules (Swift for the platform-neutral stuff, Foundation/AppKit/UIKit as appropriate for Appley stuff); name collisions would hopefully be rare enough that "@Swift.AutoClosure" or whatever hopefully won't often be necessary.
> 
> -Joe


That would solve stuff. 

How do you feel about my upcasing the attributes for readability?

-- E

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