False positive on closure_parameter_position with Swift 2.3

[jrmybrault]

Hey,

the following code triggers a parameter position violation for the completion closure :

UIView.animateWithDuration(0.3, animations: {
  self.disableInteractionRightView.alpha = 0
  }, completion: { _ in
    self.disableInteractionRightView.hidden = true
})

Do you have any idea why ?

[marcelofabri]

Are you sure this isolated example triggers? I wasn't able to reproduce it.

[BluMist]

trivial example: if you add a () inside the completion closure, it would trigger.

[marcelofabri]

Like this?

UIView.animateWithDuration(0.3, animations: {
   self.disableInteractionRightView.alpha = 0
}, completion: { _ in
   self.something()
})

I can't reproduce it this way as well. Can you provide a full example?

[BluMist]

oh, misread the issue, wrong rule, I was thinking empty_parentheses_with_trailing_closure, will create a new issue separately

[AliSoftware]

@marcelofabri To be more specific about the original issue, I saw it wth my eyes in @jrmybrault 's Xcode, the warning was about a violation of the closure_parameter_position rule and it was located on the letter c of completion:

Didn't try locally on my own Xcode though.
iirc, @jrmybrault did update to latest swiftlint very recently, like the same morning or something.

[marcelofabri]

Maybe something else in the file is affecting this. If you could reduce to a triggering example, it would be great 💯

This rule is new in SwiftLint 0.14 which as released on Homebrew today.

[AliSoftware]

@marcelofabri We actually don't work tomorrow nor the day after (Xmas period), And idk if @jrmybrault works next week tbh 😄 but will keep that in mind

[jrmybrault]

@marcelofabri : Actually, I reproduce it only on Xcode 7.x.x, it seems fine on Xcode 8.x. I thought it could be related to spaces & indentations but the settings are identical.

Xcode 7.3.1 : triggers

import UIKit

final class EmptyViewController: UIViewController {

  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

    UIView.animateWithDuration(0.3, animations: {
      self.view.alpha = 0
      }, completion: { _ in
        self.view.hidden = true
    })
  }
}

Xcode 8.2 : does not trigger

import UIKit

final class EmptyViewController: UIViewController {

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    UIView.animate(withDuration: 0.3, animations: {
      self.view.alpha = 0
    }, completion: { _ in
      self.view.isHidden = true
    })
  }
}

[marcelofabri]

@jrmybrault Thanks for doing this! I'm downloading Xcode 7.3.1 right now and will verify it later.

My theory is that SourceKit is returning different structures for this file.

[marcelofabri]

The structures are a bit different, which may explain the false positive:

Xcode 7.3.1

{
	"key.namelength": 30,
	"key.nameoffset": 83,
	"key.bodylength": 161,
	"key.accessibility": "source.lang.swift.accessibility.internal",
	"key.length": 199,
	"key.substructure": [{
		"key.nameoffset": 0,
		"key.typename": "Bool",
		"key.length": 14,
		"key.name": "animated",
		"key.kind": "source.lang.swift.decl.var.parameter",
		"key.namelength": 0,
		"key.offset": 98
	}, {
		"key.offset": 117,
		"key.nameoffset": 117,
		"key.length": 30,
		"key.name": "super.viewWillAppear",
		"key.bodyoffset": 138,
		"key.kind": "source.lang.swift.expr.call",
		"key.namelength": 20,
		"key.bodylength": 8
	}, {
		"key.bodylength": 95,
		"key.nameoffset": 150,
		"key.substructure": [{
			"key.offset": 177,
			"key.nameoffset": 0,
			"key.length": 3,
			"key.bodyoffset": 177,
			"key.bodylength": 3,
			"key.kind": "source.lang.swift.decl.var.parameter",
			"key.namelength": 0
		}, {
			"key.offset": 182,
			"key.nameoffset": 182,
			"key.length": 41,
			"key.name": "animations",
			"key.bodyoffset": 194,
			"key.kind": "source.lang.swift.decl.var.parameter",
			"key.namelength": 10,
			"key.bodylength": 29
		}, {
			"key.bodylength": 35,
			"key.nameoffset": 225,
			"key.substructure": [{
				"key.typename": "_",
				"key.nameoffset": 0,
				"key.kind": "source.lang.swift.decl.var.parameter",
				"key.length": 1,
				"key.namelength": 0,
				"key.offset": 239
			}],
			"key.length": 47,
			"key.name": "completion",
			"key.bodyoffset": 237,
			"key.kind": "source.lang.swift.decl.var.parameter",
			"key.offset": 225,
			"key.namelength": 10
		}],
		"key.length": 123,
		"key.name": "UIView.animateWithDuration",
		"key.bodyoffset": 177,
		"key.kind": "source.lang.swift.expr.call",
		"key.offset": 150,
		"key.namelength": 26
	}],
	"key.name": "viewWillAppear(_:)",
	"key.bodyoffset": 115,
	"key.attributes": [{
		"key.attribute": "source.decl.attribute.override"
	}],
	"key.kind": "source.lang.swift.decl.function.method.instance",
	"key.offset": 78
}

Xcode 8.2.1

{
	"key.namelength": 32,
	"key.nameoffset": 83,
	"key.bodylength": 164,
	"key.accessibility": "source.lang.swift.accessibility.internal",
	"key.length": 204,
	"key.substructure": [{
		"key.nameoffset": 0,
		"key.typename": "Bool",
		"key.length": 16,
		"key.name": "animated",
		"key.kind": "source.lang.swift.decl.var.parameter",
		"key.namelength": 0,
		"key.offset": 98
	}, {
		"key.offset": 119,
		"key.nameoffset": 119,
		"key.length": 30,
		"key.name": "super.viewWillAppear",
		"key.bodyoffset": 140,
		"key.kind": "source.lang.swift.expr.call",
		"key.namelength": 20,
		"key.bodylength": 8
	}, {
		"key.bodylength": 110,
		"key.nameoffset": 152,
		"key.substructure": [{
			"key.offset": 167,
			"key.nameoffset": 167,
			"key.length": 17,
			"key.name": "withDuration",
			"key.bodyoffset": 181,
			"key.kind": "source.lang.swift.expr.argument",
			"key.namelength": 12,
			"key.bodylength": 3
		}, {
			"key.offset": 186,
			"key.nameoffset": 186,
			"key.length": 39,
			"key.name": "animations",
			"key.bodyoffset": 198,
			"key.kind": "source.lang.swift.expr.argument",
			"key.namelength": 10,
			"key.bodylength": 27
		}, {
			"key.bodylength": 38,
			"key.nameoffset": 227,
			"key.substructure": [{
				"key.nameoffset": 0,
				"key.kind": "source.lang.swift.decl.var.parameter",
				"key.namelength": 0,
				"key.offset": 241,
				"key.length": 1
			}],
			"key.length": 50,
			"key.name": "completion",
			"key.bodyoffset": 239,
			"key.kind": "source.lang.swift.expr.argument",
			"key.offset": 227,
			"key.namelength": 10
		}],
		"key.length": 126,
		"key.name": "UIView.animate",
		"key.bodyoffset": 167,
		"key.kind": "source.lang.swift.expr.call",
		"key.offset": 152,
		"key.namelength": 14
	}],
	"key.name": "viewWillAppear(_:)",
	"key.bodyoffset": 117,
	"key.attributes": [{
		"key.attribute": "source.decl.attribute.override"
	}],
	"key.kind": "source.lang.swift.decl.function.method.instance",
	"key.offset": 78
}

Note that in 8.x, the parameters are inside a source.lang.swift.expr.argument, while in 7.x they're inside another source.lang.swift.decl.var.parameter.

Here're the violations that were trigged:

file.swift:8:34: warning: Unused Closure Parameter Violation: Unused parameter "animations" in a closure should be replaced with _. (unused_closure_parameter)
file.swift:10:7: warning: Unused Closure Parameter Violation: Unused parameter "completion" in a closure should be replaced with _. (unused_closure_parameter)
file.swift:10:7: warning: Closure Parameter Position Violation: Closure parameters should be on the same line as opening brace. (closure_parameter_position)