[swift-evolution] [Review] SE-0084: Allow trailing commas in parameter lists and tuples

[Patrick Smith]

I forgot to add I like this style particularly as it matches how the type is declared (below). There’s a symmetry between them all. Obviously each var in a struct doesn’t need a comma between it, so it would be nice to not have to type them in the other cases too!

public struct ImageGraphic : GraphicType {
	var imageSource: ImageSource
	var width: Dimension?
	var height: Dimension?
}


> On 13 May 2016, at 4:22 PM, Vladimir.S <svabox at gmail.com> wrote:
> 
> It seems like all problems could be solved by allowing line-break instead of comma in list:
> 
> 	public init(source: JSONObjectDecoder) throws {
> 		try self.init(
> 			imageSource: source.decode("imageSource")
> 			width: source.decodeOptional("width")
> 			height: source.decodeOptional("height")
> 		)
> 	}
> 	
> 	public func toJSON() -> JSON {
> 		return .ObjectValue([
> 			"imageSource": imageSource.toJSON()
> 			"width": width.toJSON()
> 			"height": height.toJSON()
> 		])
> 	}
> 
> Shouldn't we move in that direction? Probably in addition to allow trailing comma just to allow one to use his/her preferable formatting
> 
> On 13.05.2016 9:07, Patrick Smith via swift-evolution wrote:
>> I do it quite a lot, especially for initialising structs, enums. I use it to get the same benefits as a switch statement spread over several lines.
>> 
>> I think it’s often good to liberally apply new lines, as it aids legibility.
>> 
>> Here some sample code of mine using it:
>> 
>> extension ImageGraphic : JSONObjectRepresentable {
>> 	public init(source: JSONObjectDecoder) throws {
>> 		try self.init(
>> 			imageSource: source.decode("imageSource"),
>> 			width: source.decodeOptional("width"),
>> 			height: source.decodeOptional("height")
>> 		)
>> 	}
>> 	
>> 	public func toJSON() -> JSON {
>> 		return .ObjectValue([
>> 			"imageSource": imageSource.toJSON(),
>> 			"width": width.toJSON(),
>> 			"height": height.toJSON()
>> 		])
>> 	}
>> }
>> 
>> 
>>> On 13 May 2016, at 3:01 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> On May 12, 2016, at 4:50 PM, Joe Groff <jgroff at apple.com> wrote:
>>>>>> 	--- a.swift
>>>>>> 	+++ a.swift
>>>>>> 	 foo(
>>>>>> 	   x: 0,
>>>>>> 	-  y: 1
>>>>>> 	+  y: 1,
>>>>>> 	+  z: 2
>>>>>> 	 )
>>>>>> 
>>>>>> Trailing commas avoid this:
>>>>>> 
>>>>>> 	--- a.swift
>>>>>> 	+++ a.swift
>>>>>> 	 foo(
>>>>>> 	   x: 0,
>>>>>> 	   y: 1,
>>>>>> 	+  z: 2,
>>>>>> 	 )
>>>>> 
>>>>> You’re arguing that you want to read Swift code written like this?
>>>> 
>>>> I wouldn't mind it.
>>> 
>>> I personally find that style repulsive :-) and I haven’t seen swift code commonly doing it.  I’m not sure that we want to encourage it either.
>>> 
>>>> The standard library already uses this style for function parameters, modulo the trailing comma, and I certainly prefer it to:
>>>> 	
>>>>> 	--- a.swift
>>>>> 	+++ a.swift
>>>>> 	 foo( x: 0
>>>>> 	    , y: 1
>>>>> 	+   , z: 2
>>>>> 	    )
>>> 
>>> I agree that this is even worse, but I also haven’t seen this used in Swift code.  Have you?   Swift’s strictness with argument labels makes any of this pretty unappealing to use.
>>> 
>>> If we were really concerned about this, a narrower way to solve the same problem would be to allow a comma before the ), but *only* when there is a newline between them.  I still don’t see why we’d want to encourage this though.
>>> 
>>> -Chris
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