[swift-evolution] [Further Discussion] Naming Attributes

[Joe Groff]

> On Feb 19, 2016, at 1:10 PM, Erica Sadun <erica at ericasadun.com> wrote:
> 
> 
>> On Feb 19, 2016, at 2:04 PM, Joe Groff <jgroff at apple.com <mailto: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?

Uppercasing seems reasonable to me.

-Joe

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