π SwiftRewriter
Swift code formatter using SwiftSyntax.
Requirements: Swift 5.1 (Xcode 11.0) + SwiftSyntax 0.50100.0
See also my iOSConf SG 2019 talk for more detail:
- Slide: Making your own Code Formatter in Swift - Speaker Deck
- Video: Make your own code formatter in Swift β iOS Conf SG 2019 β Learn Talks
Overview
SwiftRewriter: Collection of reusable & composableSyntaxRewritersswift-rewriter: Simple command-line executable
How to use
$ swift build
$ swift run swift-rewriter help
Available commands:
help Display general or command-specific help
print-ast print AST from file or string
run Auto-correct code in the file or directory
# Auto-correct code in the directory
$ swift run swift-rewriter run --path /path/to/file-or-directoryConfiguration
In swift-rewriter CLI tool, rewriting rules are configured in rewriter.swift (configuration file e.g. yaml or json is not supported yet).
Please change the configuration as you like (you can make your own rewriter and combine!), and swift build & run.
// rewriter.swift
import SwiftRewriter
var rewriter: Rewriter {
// Comment
HeaderCopyrightTrimmer()
// Move
>>> ImportSorter()
// >>> ExtensionIniter() // not useful for everyone
// Token
>>> DecimalLiteralUnderscorer()
>>> SemicolonTrimmer()
// Newline (whitespace)
// >>> ExtraNewliner() // not useful for everyone
>>> ElseNewliner(newline: false)
>>> MethodChainNewliner()
// Indent (whitespace)
>>> Indenter(.init(
perIndent: .spaces(4),
shouldIndentSwitchCase: false,
shouldIndentIfConfig: false,
skipsCommentedLine: true
))
// Space (whitespace)
// >>> ExtraSpaceTrimmer() // may disturb manually-aligned code
>>> ColonSpacer(spaceBefore: false, spaceAfter: true)
>>> TernaryExprSpacer()
>>> BinaryOperatorSpacer(spacesAround: true)
// Ignore to not distrub user-aligned multiple assignments
// TODO: Improve multiple assignment alignment
// >>> EqualSpacer(spacesAround: true)
>>> ArrowSpacer(spaceBefore: true, spaceAfter: true)
>>> LeftBraceSpacer(spaceBefore: true)
>>> LeftParenSpacer(spaceBefore: true)
>>> TrailingSpaceTrimmer()
}Rewriter examples
Indenter
Better right-brace position
@@ β1,6 +1,6 @@
βlets
β .code {
β }
β .format {
-} // this!!!
+ } // this!!!P.S. This is the primary goal of making SwiftRewriter.
First-item-aware indent
struct Foo {
init(bool: Bool,
int: Int) {
self.bool = bool
if true {
print()
}
run { x in
print(x,
y,
z)
}
}
}will be:
struct Foo {
init(bool: Bool,
int: Int) {
self.bool = bool
if true {
print()
}
run { x in
print(x,
y,
z)
}
}
}HeaderCopyrightTrimmer
@@ β1,10 +1,2 @@
-//
-// example.swift
-// SwiftRewriter
-//
-// Created by Yasuhiro Inami on 2018-12-09.
-// Copyright Β© 2018 Yasuhiro Inami. All rights reserved.
-//
-
β// All your code are belong to us.ImportSorter
import C
import B
func foo() {}
import A
import Dwill be:
import A
import B
import C
import D
func foo() {}ExtensionIniter
This rewriter moves the code to enable struct's memberwise initializer.
struct Foo {
let int: Int
init(int: Int) {
self.int = int
}
init() {
self.int = 0
}
}@@ β1,9 +1,12 @@
βstruct Foo {
β let int: Int
+}
+
+extension Foo {
β init(int: Int) {
β self.int = int
β }
β init() {
β self.int = 0
β }
β}ExtraNewliner (Work in Progress)
This rewriter adds a newline when code is too dense.
import Foundation
var computed1: Int = 1
var computed2: Int = { return 2 }
/// doc
var computed3: Int = { return 3 }
/// doc
var computedBlock: String {
return ""
}
func send() -> Observable<Void> {
return apiSession
.send(request)
.do(onError: { [weak self] error in
guard let me = self else { return }
me.doSomething()
})
.do(onError: { [weak self] error in
guard let me = self else { return }
me.doSomething()
me.doSomething()
})
}will be:
import Foundation
var computed1: Int = 1
var computed2: Int = { return 2 }
/// doc
var computed3: Int = { return 3 }
/// doc
var computedBlock: String {
return ""
}
func send() -> Observable<Void> {
return apiSession
.send(request)
.do(onError: { [weak self] error in
guard let me = self else { return }
me.doSomething()
})
.do(onError: { [weak self] error in
guard let me = self else { return }
me.doSomething()
me.doSomething()
})
}Roadmap / TODO
- Add configuration file support
- Automatic code folding
- Move properties above method (for "states" readability)
- Move inner types to
extensionscope (for "states" readability) - Align multiline
=assignments - (Your idea comes here
π‘ )
Acknowledgement
- Improving Swift Tools with libSyntax by @harlanhaskins
- Creating Refactoring Transformations for Swift by @nkcsgexi
- try! Swift Tokyo 2018 - AST Meta-programming by @kishikawakatsumi
- SwiftSyntax - NSHipster by @mattt
- SwiftLint and SwiftSyntax benchmarking by @jpsim et al.