"Attributes should be on their own line" rule

[marcelofabri]

I think we should have a rule that some (that's the tricky) part attributes should be on their own line.

The attributes that I'd like to see in that list are:

• @discardableResult
• @available
• @NSApplicationMain
• @UIApplicationMain
• @IBDesignable

The attributes that I particularly use on the same line:

• @GKInspectable
• @objc
• @nonobjc
• @NSCopying
• @NSManaged
• @testable
• @IBAction
• @IBOutlet
• @IBInspectable

It seems to me that all the attributes that I use on the same line are in these categories:

1. Applied to a var
2. Applied to import
3. @objc or @nonobj

I'd be OK with @objc and @nonobj being on their own line for functions/types but I don't think we can just use the "where is this attribute" rule because of @available.

[keith]

👍🏻 this seems useful. For 3 we also put those on their own line. But that's just us!

[marcelofabri]

I've started looking into this, but I'm having trouble because the AST doesn't expose the range for the attribute:

$ sourcekitten structure --text "@IBOutlet private var label: UILabel"
{
  "key.substructure" : [
    {
      "key.kind" : "source.lang.swift.decl.var.global",
      "key.offset" : 18,
      "key.attributes" : [
        {
          "key.attribute" : "source.decl.attribute.iboutlet"
        }
      ],
      "key.nameoffset" : 22,
      "key.namelength" : 5,
      "key.length" : 18,
      "key.accessibility" : "source.lang.swift.accessibility.private",
      "key.setter_accessibility" : "source.lang.swift.accessibility.private",
      "key.typename" : "UILabel",
      "key.name" : "label"
    }
  ],
  "key.offset" : 0,
  "key.diagnostic_stage" : "source.diagnostic.stage.swift.parse",
  "key.length" : 36
}

I can get it from sourcekitten syntax, but the type is source.lang.swift.syntaxtype.attribute.builtin, which is used for other things (such as private).

$ sourcekitten syntax --text "@IBOutlet private var label: UILabel"
[
  {
    "offset" : 0,
    "length" : 9,
    "type" : "source.lang.swift.syntaxtype.attribute.builtin"
  },
  {
    "offset" : 10,
    "length" : 7,
    "type" : "source.lang.swift.syntaxtype.attribute.builtin"
  },
  {
    "offset" : 18,
    "length" : 3,
    "type" : "source.lang.swift.syntaxtype.keyword"
  },
  {
    "offset" : 22,
    "length" : 5,
    "type" : "source.lang.swift.syntaxtype.identifier"
  },
  {
    "offset" : 29,
    "length" : 7,
    "type" : "source.lang.swift.syntaxtype.typeidentifier"
  }
]

How bad would be checking if it starts with @? 😅

[keith]

It might be worth looking into how the valid documentation comment stuff works. As we don't get the offset for the comment either, but still access it.

FWIW we have a rule for @objc on a newline implemented and we just used regex.

[marcelofabri]

From what I've seen, the documentation rules use regex. I've opened #847 with my approach.

[ghost]

FWIW, Erica Sadun did a quick poll around styling of attributes: http://ericasadun.com/2016/10/02/quick-style-survey/

[marcelofabri]

Thanks for sharing! I've based my opinions on what I've seen in then Apple docs, although I forgot that you can use @objc to specify a name.