Enable swift-format checking (apple#711)

Adopts the common swift-mmio and swift-argument-parser format and enables CI checking.

Fixes: apple#702

Author: rauhul

.github/workflows/lint.yml

@@ -5,11 +5,25 @@ on:
     types: [opened, reopened, synchronize]
 
 jobs:
+  validate_format_config:
+    name: Validate Format Config
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+
+      - name: Install apt dependencies
+        run: sudo apt-get -qq update && sudo apt-get -qq -y install curl
+
+      - name: Compare against swift-mmio swift-format config
+        run: |
+          curl -sL https://raw.githubusercontent.com/apple/swift-mmio/refs/heads/main/.swift-format -o .swift-format-mmio
+          diff .swift-format .swift-format-mmio
+
   soundness:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
-      format_check_enabled: false  # bug: https://github.com/apple/swift-argument-parser/issues/702
       license_header_check_enabled: false  # feature: https://github.com/swiftlang/github-workflows/issues/78
       license_header_check_project_name: "Swift Argument Parser"  # bug: https://github.com/swiftlang/github-workflows/issues/76
       shell_check_enabled: false  # bug: https://github.com/apple/swift-argument-parser/issues/703

.swift-format

@@ -0,0 +1,71 @@
+{
+  "fileScopedDeclarationPrivacy" : {
+    "accessLevel" : "private"
+  },
+  "indentation" : {
+    "spaces" : 2
+  },
+  "indentConditionalCompilationBlocks" : false,
+  "indentSwitchCaseLabels" : false,
+  "lineBreakAroundMultilineExpressionChainComponents" : false,
+  "lineBreakBeforeControlFlowKeywords" : false,
+  "lineBreakBeforeEachArgument" : false,
+  "lineBreakBeforeEachGenericRequirement" : false,
+  "lineLength" : 80,
+  "maximumBlankLines" : 1,
+  "multiElementCollectionTrailingCommas" : true,
+  "noAssignmentInExpressions" : {
+    "allowedFunctions" : [
+      "XCTAssertNoThrow"
+    ]
+  },
+  "prioritizeKeepingFunctionOutputTogether" : false,
+  "respectsExistingLineBreaks" : true,
+  "rules" : {
+    "AllPublicDeclarationsHaveDocumentation" : false,
+    "AlwaysUseLiteralForEmptyCollectionInit" : true,
+    "AlwaysUseLowerCamelCase" : true,
+    "AmbiguousTrailingClosureOverload" : false,
+    "BeginDocumentationCommentWithOneLineSummary" : true,
+    "DoNotUseSemicolons" : true,
+    "DontRepeatTypeInStaticProperties" : true,
+    "FileScopedDeclarationPrivacy" : true,
+    "FullyIndirectEnum" : true,
+    "GroupNumericLiterals" : true,
+    "IdentifiersMustBeASCII" : true,
+    "NeverForceUnwrap" : true,
+    "NeverUseForceTry" : true,
+    "NeverUseImplicitlyUnwrappedOptionals" : true,
+    "NoAccessLevelOnExtensionDeclaration" : true,
+    "NoAssignmentInExpressions" : true,
+    "NoBlockComments" : true,
+    "NoCasesWithOnlyFallthrough" : true,
+    "NoEmptyTrailingClosureParentheses" : true,
+    "NoLabelsInCasePatterns" : true,
+    "NoLeadingUnderscores" : false,
+    "NoParensAroundConditions" : true,
+    "NoPlaygroundLiterals" : true,
+    "NoVoidReturnOnFunctionSignature" : true,
+    "OmitExplicitReturns" : true,
+    "OneCasePerLine" : true,
+    "OneVariableDeclarationPerLine" : true,
+    "OnlyOneTrailingClosureArgument" : true,
+    "OrderedImports" : true,
+    "ReplaceForEachWithForLoop" : true,
+    "ReturnVoidInsteadOfEmptyTuple" : true,
+    "TypeNamesShouldBeCapitalized" : true,
+    "UseEarlyExits" : false,
+    "UseExplicitNilCheckInConditions" : true,
+    "UseLetInEveryBoundCaseVariable" : true,
+    "UseShorthandTypeNames" : true,
+    "UseSingleLinePropertyGetter" : true,
+    "UseSynthesizedInitializer" : true,
+    "UseTripleSlashForDocumentationComments" : true,
+    "UseWhereClausesInForLoops" : false,
+    "ValidateDocumentationComments" : true
+  },
+  "spacesBeforeEndOfLineComments": 2,
+  "spacesAroundRangeFormationOperators" : false,
+  "tabWidth" : 2,
+  "version" : 1
+}

Examples/color/Color.swift

@@ -17,7 +17,8 @@ struct Color: ParsableCommand {
   @Option(help: "Your favorite color.")
   var fav: ColorOptions
 
-  @Option(help: .init("Your second favorite color.", discussion: "This is optional."))
+  @Option(
+    help: .init("Your second favorite color.", discussion: "This is optional."))
   var second: ColorOptions?
 
   func run() {

Examples/count-lines/CountLines.swift

@@ -15,58 +15,57 @@ import Foundation
 @main
 @available(macOS 12, *)
 struct CountLines: AsyncParsableCommand {
-    @Argument(
-        help: "A file to count lines in. If omitted, counts the lines of stdin.",
-        completion: .file(), transform: URL.init(fileURLWithPath:))
-    var inputFile: URL? = nil
-    
-    @Option(help: "Only count lines with this prefix.")
-    var prefix: String? = nil
-    
-    @Flag(help: "Include extra information in the output.")
-    var verbose = false
+  @Argument(
+    help: "A file to count lines in. If omitted, counts the lines of stdin.",
+    completion: .file(), transform: URL.init(fileURLWithPath:))
+  var inputFile: URL? = nil
+
+  @Option(help: "Only count lines with this prefix.")
+  var prefix: String? = nil
+
+  @Flag(help: "Include extra information in the output.")
+  var verbose = false
 }
 
 @available(macOS 12, *)
 extension CountLines {
-    var fileHandle: FileHandle {
-        get throws {
-            guard let inputFile else {
-                return .standardInput
-            }
-            return try FileHandle(forReadingFrom: inputFile)
-        }
+  var fileHandle: FileHandle {
+    get throws {
+      guard let inputFile else {
+        return .standardInput
+      }
+      return try FileHandle(forReadingFrom: inputFile)
     }
-    
-    func printCount(_ count: Int) {
-        guard verbose else {
-            print(count)
-            return
-        }
-        
-        if let filename = inputFile?.lastPathComponent {
-            print("Lines in '\(filename)'", terminator: "")
-        } else {
-            print("Lines from stdin", terminator: "")
-        }
-        
-        if let prefix {
-            print(", prefixed by '\(prefix)'", terminator: "")
-        }
-        
-        print(": \(count)")
+  }
+
+  func printCount(_ count: Int) {
+    guard verbose else {
+      print(count)
+      return
+    }
+
+    if let filename = inputFile?.lastPathComponent {
+      print("Lines in '\(filename)'", terminator: "")
+    } else {
+      print("Lines from stdin", terminator: "")
     }
-    
-    mutating func run() async throws {
-        let countAllLines = prefix == nil
-        let lineCount = try await fileHandle.bytes.lines.reduce(0) { count, line in
-            if countAllLines || line.starts(with: prefix!) {
-                return count + 1
-            } else {
-                return count
-            }
-        }
-        
-        printCount(lineCount)
+
+    if let prefix {
+      print(", prefixed by '\(prefix)'", terminator: "")
+    }
+
+    print(": \(count)")
+  }
+
+  mutating func run() async throws {
+    var lineCount = 0
+    for try await line in try fileHandle.bytes.lines {
+      if let prefix {
+        lineCount += line.starts(with: prefix) ? 1 : 0
+      } else {
+        lineCount += 1
+      }
     }
+    printCount(lineCount)
+  }
 }