Initial implementation

Sources/Logging OSLog/Logging OSLog.swift

@@ -0,0 +1,75 @@
+import Foundation
+import os
+import Logging
+
+public struct LoggingOSLog: LogHandler {
+	public var logLevel: Logging.Logger.Level = .info
+	public var metadata: Logging.Logger.Metadata = [:]
+	public var metadataProvider: Logging.Logger.MetadataProvider?
+	private let oslogger: os.Logger
+
+	public init(label: String) {
+		let lastDotPosition = label.lastIndex(of: ".") ?? label.startIndex
+		let frontPart = label.prefix(upTo: lastDotPosition)
+		let backPart = label.suffix(from: lastDotPosition)
+		guard frontPart.count > 0 else {
+			let subsystem = Bundle.main.bundleIdentifier ?? "SwiftLogToOsLog"
+			self.init(subsystem: subsystem, category: label)
+			return
+		}
+		self.init(subsystem: String(frontPart), category: String(backPart))
+	}
+
+	public init(
+		subsystem: String = Bundle.main.bundleIdentifier ?? "SwiftLogToOsLog",
+		category: String,
+		logLevel: Logging.Logger.Level = .debug
+	) {
+		self.oslogger = os.Logger(subsystem: subsystem, category: category)
+		self.logLevel = logLevel
+	}
+
+	public init(oslog: os.Logger, logLevel: Logging.Logger.Level = .debug) {
+		self.oslogger = oslog
+		self.logLevel = logLevel
+	}
+
+	public func log(
+		level: Logging.Logger.Level,
+		message: Logging.Logger.Message,
+		metadata: Logging.Logger.Metadata?,
+		source: String,
+		file: String,
+		function: String,
+		line: UInt
+	) {
+		let metadataCSV = Self.joinMetadata(self.metadata, self.metadataProvider?.get(), metadata)
+		let messageParts = [message.description, metadataCSV]
+
+		let message = messageParts.compactMap { $0 }.joined(separator: " -> ")
+		self.oslogger.log(level: OSLogType.from(loggerLevel: level), "\(message)")
+	}
+
+	public subscript(metadataKey metadataKey: String) -> Logging.Logger.Metadata.Value? {
+		get {
+			return self.metadata[metadataKey]
+		}
+		set {
+			self.metadata[metadataKey] = newValue
+		}
+	}
+	
+	private static func joinMetadata(_ metadataList: Logging.Logger.Metadata?...) -> String? {
+		var metadataAggregator: Logging.Logger.Metadata = [:]
+		for metadata in metadataList {
+			guard let metadata = metadata else { continue }
+			metadataAggregator.merge(metadata) { return $1 }
+		}
+		return Self.joinMetadata(metadataAggregator)
+	}
+
+	private static func joinMetadata(_ metadata: Logging.Logger.Metadata, with separator: String = ", ") -> String? {
+		guard !metadata.isEmpty else { return nil }
+		return metadata.map { "\($0) = \($1)" }.joined(separator: separator)
+	}
+}

Sources/Logging OSLog/OSLog Extension.swift

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+import Logging
+import os
+
+extension OSLogType {
+	static func from(loggerLevel: Logging.Logger.Level) -> Self {
+		switch loggerLevel {
+		case .trace:
+			return .debug
+		case .debug:
+			return .debug
+		case .info:
+			return .info
+		case .notice:
+			return .default
+		case .warning:
+			return .info
+		case .error:
+			return .error
+		case .critical:
+			return .fault
+		}
+	}
+}