Allow Boolean encoding to be governed by new BoolEncodingStrategy

Sources/SwiftCSVEncoder/CSVEncodable.swift

@@ -82,7 +82,9 @@ extension Double: CSVEncodable {
 
 extension Bool: CSVEncodable {
     public func encode(configuration: CSVEncoderConfiguration) -> String {
-        self == true ? "true" : "false"
+        let (trueValue, falseValue) = configuration.boolEncodingStrategy.encodingValues
+
+        return self == true ? trueValue : falseValue
     }
 }
 

Sources/SwiftCSVEncoder/CSVEncoderConfiguration.swift

@@ -16,10 +16,20 @@ public struct CSVEncoderConfiguration {
     /// The default strategy is the ``DateEncodingStrategy-swift.enum/iso8601`` strategy.
     public private(set) var dateEncodingStrategy: DateEncodingStrategy = .iso8601
 
+    /// The strategy to use when encoding Boolean values.
+    ///
+    /// The default strategy is the ``BoolEncodingStrategy-swift.enum/trueFalse`` strategy.
+    public private(set) var boolEncodingStrategy: BoolEncodingStrategy = .trueFalse
+
     /// Creates a new instance of ``CSVEncoderConfiguration`` with the requisite configuration values
     /// - Parameter dateEncodingStrategy: The strategy to use when encoding dates
-    public init(dateEncodingStrategy: DateEncodingStrategy) {
+    /// - Parameter boolEncodingStrategy: The strategy to use when encoding Boolean values
+    public init(
+        dateEncodingStrategy: DateEncodingStrategy = .iso8601,
+        boolEncodingStrategy: BoolEncodingStrategy = .trueFalse
+    ) {
         self.dateEncodingStrategy = dateEncodingStrategy
+        self.boolEncodingStrategy = boolEncodingStrategy
     }
 
     /// The strategy to use when encoding `Date` objects for CSV output.
@@ -34,10 +44,45 @@ public struct CSVEncoderConfiguration {
         /// - Parameter custom: A closure that receives the `Date` to encode, and returns the `String` to include in the CSV output.
         case custom(@Sendable (Date) -> String)
     }
-
+
+    /// The strategy to use when encoding `Bool` objects for CSV output.
+    public enum BoolEncodingStrategy {
+        /// The strategy that emits `true` and `false` for Boolean fields
+        case trueFalse
+        /// The strategy that emits `TRUE` and `FALSE` for Boolean fields
+        case trueFalseUppercase
+        /// The strategy that emite `yes` and `no` for Boolean fields
+        case yesNo
+        /// The strategy that emits `YES` and `NO` for Boolean fields
+        case yesNoUppercase
+        /// The strategy that emits `1` and `0` for Boolean fields
+        case integer
+        /// A custom strategy that emitss the custom supplied strings for Boolean fields
+        case custom(true: String, false: String)
+    }
+
     /// A default set of configuration values.
     ///
     /// This configuration set will be used when a ``CSVTable`` is initialized with setting a custom
     /// configuration.
-    public static var `default`: CSVEncoderConfiguration = .init(dateEncodingStrategy: .iso8601)
+    public static var `default`: CSVEncoderConfiguration = CSVEncoderConfiguration()
+}
+
+internal extension CSVEncoderConfiguration.BoolEncodingStrategy {
+    var encodingValues: (String, String) {
+        switch self {
+        case .trueFalse:
+            return ("true", "false")
+        case .trueFalseUppercase:
+            return ("TRUE", "FALSE")
+        case .yesNo:
+            return ("yes", "no")
+        case .yesNoUppercase:
+            return ("YES", "NO")
+        case .integer:
+            return ("1", "0")
+        case .custom(let trueValue, let falseValue):
+            return (trueValue, falseValue)
+        }
+    }
 }

Sources/SwiftCSVEncoder/SwiftCSVEncoder.docc/SwiftCSVEncoder.md

@@ -52,6 +52,8 @@ CSVColumn("Description", \.description)
 
 ``SwiftCSVEncoder`` adds ``CSVEncodable`` conformance to the Swift primitives `String`, `Int`, `Double`, `Bool` and Foundation data types `Date` and `UUID`. Optional forms are automatically handled, with `nil` values being output as empty cells.
 
+``CSVTable/init(columns:configuration:)`` optionally takes a `configuration:` object that specifies strategies for converting `Date` and `Bool` values into strings. This can be essential for some CSV importers which expect columns of those types to be in a specific format in order to correctly recognise them. 
+
 To generate the CSV file, call ``CSVTable/export(rows:)``. The return value is the full CSV file, including a header row. String items will be enclosed in double quotes where needed:
 
 ```csv

Tests/SwiftCSVEncoderTests/CSVEncodableTests.swift

@@ -74,15 +74,87 @@ final class CSVEncodableTests: XCTestCase {
         XCTAssertEqual(date.encode(configuration: configuration), "Custom returned value")
     }
 
-    func testBoolTrueEncodedAsString() {
+    func testBoolTrueEncodedAsStringByDefault() {
         let input: Bool = true
 
         XCTAssertEqual(input.encode(configuration: .default), "true")
     }
 
-    func testBoolFalseEncodedAsString() {
+    func testBoolFalseEncodedAsStringByDefault() {
         let input: Bool = false
 
         XCTAssertEqual(input.encode(configuration: .default), "false")
     }
+
+    func testBoolTrueEncodedAsStringByTrueFalse() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .trueFalse)), "true")
+    }
+
+    func testBoolFalseEncodedAsStringByTrueFalse() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .trueFalse)), "false")
+    }
+
+    func testBoolTrueEncodedAsStringByTrueFalseUppercase() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .trueFalseUppercase)), "TRUE")
+    }
+
+    func testBoolFalseEncodedAsStringByTrueFalseUppercase() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .trueFalseUppercase)), "FALSE")
+    }
+
+    func testBoolTrueEncodedAsStringByYesNo() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .yesNo)), "yes")
+    }
+
+    func testBoolFalseEncodedAsStringByYesNo() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .yesNo)), "no")
+    }
+
+    func testBoolTrueEncodedAsStringByYesNoUppercase() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .yesNoUppercase)), "YES")
+    }
+
+    func testBoolFalseEncodedAsStringByYesNoUppercase() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .yesNoUppercase)), "NO")
+    }
+
+    func testBoolTrueEncodedAsStringByInteger() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .integer)), "1")
+    }
+
+    func testBoolFalseEncodedAsStringByInteger() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .integer)), "0")
+    }
+
+    func testBoolTrueEncodedAsCustom() {
+        let input: Bool = true
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .custom(true: "❤️", false: "☠️"))), "❤️")
+    }
+
+    func testBoolFalseEncodedAsCustom() {
+        let input: Bool = false
+
+        XCTAssertEqual(input.encode(configuration: CSVEncoderConfiguration(boolEncodingStrategy: .custom(true: "❤️", false: "☠️"))), "☠️")
+    }
 }