swift-mode

Major-mode for Apple’s Swift programming language.

Installation

Install swift-mode package from MELPA.

To install without MELPA, download latest release and execute M-x package-install-file for the .tar archive.

Features

Font Lock

Indentation

switch foo {
case let .P1(x)
       where
         x > 0,
     let .P2(x)
       where
         x > 0:
    bar()
      .then { x in
          return baz(x)
      }
      .then {(
               x,
               y
             ) in
          return moo(x + y)
      }
}
// Hanging brace
let x = [
  1,
  2,
  3
]
// Brace on its own line
let y =
  [
    1,
    2,
    3
  ]
// Utrecht style
let z =
  [ 1
  , 2
  , 3
  ]

forward-sexp
beginning-of-defun, end-of-defun, mark-defun, and narrow-to-defun.
beginning-of-sentence, end-of-sentence, kill-sentence, backward-kill-sentence, mark-sentence, and narrow-to-sentence.
A sentence is a statement outside comments or strings, or an ordinal sentence inside comments or strings.
indent-new-comment-line
Imenu
Running Swift REPL in a buffer (M-x run-swift)
Build Swift module (M-x swift-mode:build-swift-module)
Build iOS app (M-x swift-mode:build-ios-app)
Running debugger on Swift module (M-x swift-mode:debug-swift-module)
Running debugger on iOS app in simulator or device (M-x swift-mode:debug-ios-app)
(ios-deploy is required to debug on device).

This package does not provide flycheck. See flycheck-swift.

Limitations

Some syntax constructs removed from Swift 3.0 are not supported:

C-style for-loop: for var i = 1; i < 10; i++ { }

Multiple assignments in single if let:

if let x = x,
       y = y {
}

Use multiple let instead:

if let x = x,
   let y = y {
}

Indentation may not accurate. For example, foo(Bar < A, B > (c)) can be indented like either

foo(Bar < A,
    B > (c)) // Passing two Boolean arguments to foo

foo(Bar < A,
          B > (c)) // Passing a new Bar with two type arguments and a value

The Swift compiler disambiguates this case using tokens after >, but those tokens may not available at editing time. We use some heuristic for this.

Another example is difficulty of handling of colons. We have to pair all ? and : of conditional operators to decide indentation of the below snippet. This is a future work.

switch foo {
  case let P(x) where x is Foo? ? a ? b : c ?? d : e ? f : g :
    h ? i?.j() : k()
}
switch foo {
  case let P(x) where (x is Foo?) ? (a ? b : c ?? d) : (e ? f : g) :
    h ? i?.j() : k()
}

Yet another difficult case is consistency of blocks. We want to indent method chains like this:

var x = foo
  .then { x in
      aaa
  }
  .then { x in
      aaa
  }

while we also want to indent the body of if like this:

if anotherVeryLongVariableName
     .veryLongPropertyName {
    aaa
}

That is, we have to indent the closing brace with offset if it is a part of expressions while it should be aligned with the beginning of the statement/declaration if it is a part of a statement/declaration.

Then, how should we indent the following code when the cursor is before @?

var x = foo
  .bar {
    @

This could be

var x = foo
  .bar {
    @abc willSet {
        aaa
    }
}
// property declaration

var x = foo
  .bar {
      @abc var x = 1
      x
  }
// property initialization

Both are syntactically correct code. We cannot handle this case properly. This is also a future work.

Other example is regex literals and custom operators. The following example is valid Swift code with regex literals and custom operators.

let x = /^/ /^/ /^/

We parse them as regex literals rather than custom operators for now.

Hacking

To build the package locally, run make package.

To install the built package, run make install.

To run tests, run make test.

For other commands, run make help.

Official swift-mode.el by Apple: Seems still in very early stage for now. We cannot contribute to it due to the license incompatibility.
sourcekit-lsp: Language Server Protocol implementation for Swift and C-based languages.
lsp-sourcekit: Emacs client for lsp-sourcekit.
swift-helpful: Shows documentation about Swift keywords, attributes, and API.
company-sourcekit: Completion for Swift projects via SourceKit with the help of SourceKitten.
flycheck-swift: Flycheck extensions for Swift.
swift-playground-mode: Emacs support for Swift playgrounds.
swift-format: Formatter for Swift by Apple (swift format command).
SwiftRewriter: Formatter for Swift using SwiftSyntax.
SwiftFormat: Formatter for Swift.

Contributing

Yes, please do! See CONTRIBUTING for guidelines.

Acknowledgements

The REPL code is based on js-comint.

Thanks to the following original developer and users for their contributions:

@chrisbarrett (Chris Barrett)
@ap4y (Arthur Evstifeev)
@bbatsov (Bozhidar Batsov)
@ckruse (Christian Kruse)
@syohex (Syohei Yoshida)
@uk-ar (Yuuki Arisawa)
@msanders (Michael Sanders)

You can find a full list of those people here.

Thanks to @purcell (Steve Purcell) for advices on the code and arrangement for merging swift3-mode and swift-mode.