Initialize Positional with a type that conforms to ArgumentGroup

.github/workflows/ci.yml

@@ -11,25 +11,27 @@ on:
 
 jobs:
   lint:
-    runs-on: macos-13
+    runs-on: macos-14
     environment: default
     steps:
       - uses: actions/checkout@v4
       - name: SwiftFormat version
         run: swiftformat --version
       - name: Format lint
         run: swiftformat --lint .
+      - name: Install swiftlint
+        run: brew install swiftlint
       - name: SwiftLint version
         run: swiftlint --version
       - name: Lint
         run: swiftlint lint --quiet
   macos-test:
-    runs-on: macos-13
+    runs-on: macos-14
     environment: default
     strategy:
       matrix:
-        xcode: ["14.3", "15.0"]
-        # Swift: 5.8  , 5.9
+        xcode: ["14.3.1", "15.2", "15.4", "16.0", "16.1"]
+        # Swift: 5.8,      5.9     5.10,   6.0,    6.0.2
     steps:
       - uses: actions/checkout@v4
       - name: Select Xcode ${{ matrix.xcode }}
@@ -47,6 +49,6 @@ jobs:
     environment: default
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run Tests
         run: swift test --parallel

Sources/ArgumentEncoding/PositionalArgument.swift

@@ -226,6 +226,33 @@ extension Positional {
     }
 }
 
+// MARK: Convenience initializers when Value: ArgumentGroup
+
+extension Positional where Value: ArgumentGroup {
+    /// Initializes a new positional when not used as a `@propertyWrapper`
+    ///
+    /// - Parameters
+    ///     - wrappedValue: The underlying value
+    public init(value: Value) {
+        wrappedValue = value
+        unwrap = Self.unwrap(_:)
+    }
+
+    /// Initializes a new positional when used as a `@propertyWrapper`
+    ///
+    /// - Parameters
+    ///     - wrappedValue: The underlying value
+    public init(wrappedValue: Value) {
+        self.wrappedValue = wrappedValue
+        unwrap = Self.unwrap(_:)
+    }
+
+    @Sendable
+    public static func unwrap(_ value: Value) -> [String] {
+        value.arguments()
+    }
+}
+
 // MARK: ExpressibleBy...Literal conformances
 
 extension Positional: ExpressibleByIntegerLiteral where Value: BinaryInteger, Value.IntegerLiteralType == Int {

Tests/ArgumentEncodingTests/ArgumentGroupTests.swift

@@ -250,28 +250,14 @@ final class ArgumentGroupTests: XCTestCase {
     }
 }
 
-#if swift(>=6)
-    extension Array: @retroactive ArgumentGroup, @retroactive FormatterNode {
-        public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
+extension Array: ArgumentGroup, FormatterNode {
+    public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
 
-        public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
-    }
-
-    extension Dictionary: @retroactive ArgumentGroup, @retroactive FormatterNode {
-        public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
-
-        public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
-    }
-#else
-    extension Array: ArgumentGroup, FormatterNode {
-        public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
-
-        public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
-    }
+    public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
+}
 
-    extension Dictionary: ArgumentGroup, FormatterNode {
-        public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
+extension Dictionary: ArgumentGroup, FormatterNode {
+    public var flagFormatter: ArgumentEncoding.FlagFormatter { FlagFormatter(prefix: .doubleDash) }
 
-        public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
-    }
-#endif
+    public var optionFormatter: ArgumentEncoding.OptionFormatter { OptionFormatter(prefix: .doubleDash) }
+}

Tests/ArgumentEncodingTests/PositionalTests.swift

@@ -28,6 +28,15 @@ final class PositionalTests: XCTestCase {
         let args = container.arguments()
         XCTAssertEqual(args, ["positional-argument"])
     }
+
+    func testPositionalArgumentGroup() throws {
+        let positional =
+            Positional(
+                value: Container(configuration: RawValueCustomStringConvertible(rawValue: "positional-argument"))
+            )
+        let args = positional.arguments()
+        XCTAssertEqual(args, ["positional-argument"])
+    }
 }
 
 private struct RawValueCustomStringConvertible: RawRepresentable, CustomStringConvertible {