Swift Format

swift-format.swift

import Foundation
import SwiftSyntax

/// Ensures all opening braces and brackets appear on the same line
/// as the previous token.
class FixBraces: SyntaxRewriter {
  override func visit(_ token: TokenSyntax) -> Syntax {
    switch token.tokenKind {
    case .leftBrace, .leftSquareBracket:
      return token.withLeadingTrivia(.spaces(1))
    default:
      return token
    }
  }
}

/// Ensure all colons have 0 spaces before them.
class FixColons: SyntaxRewriter {
  override func visit(_ token: TokenSyntax) -> Syntax {
    // The child after this one, if there is one.
    let sibling = token.parent?.child(at: token.indexInParent + 1)

    // If the next token is a colon, remove the trailing trivia from this
    // token.
    guard let nextToken = sibling as? TokenSyntax,
          case .colon = nextToken.tokenKind else { return token }

    return token.withoutTrailingTrivia()
  }
}

/// Ensures all large integers have _'s in each of the hundreds/
/// thousands/etc place.
class FixIntegers: SyntaxRewriter {
  func reSplitInteger(_ literal: String) -> String {
    let pieces = literal.split(separator: "_")
    let noSplit = pieces.joined(separator: "")
    var fixed = ""
    for (offset, char) in noSplit.reversed().enumerated() {
      if offset != 0 && offset % 3 == 0 {
        fixed.insert("_", at: fixed.startIndex)
      }
      fixed.insert(char, at: fixed.startIndex)
    }
    return fixed
  }

  override func visit(_ token: TokenSyntax) -> Syntax {
    guard case .integerLiteral(let text) = token.tokenKind else {
      return token
    }

    let fixed = reSplitInteger(text)
    return token.withKind(.integerLiteral(fixed))
  }
}

guard CommandLine.arguments.count > 1 else {
  print("usage: fixintegers [file]")
  exit(-1)
}

do {
  let url = URL(fileURLWithPath: CommandLine.arguments[1])
  let file = try Syntax.parse(url)
  let integersFixed = FixIntegers().visit(file) 
  let bracesFixed = FixBraces().visit(integersFixed)
  let colonsFixed = FixColons().visit(bracesFixed)

  try "\(colonsFixed)".write(to: url, atomically: true,
                             encoding: .utf8)
} catch {
  print("error: \(error)")
  exit(-1)
}