From 7863e4307923f8a825f38b98f08513a1e0efd385 Mon Sep 17 00:00:00 2001
From: Tamilarasan Raja <aiwithtamil14@gmail.com>
Date: Sun, 28 Jun 2026 03:54:50 +0530
Subject: [PATCH] ContainerLog: add metadataProvider to LogHandler
 implementations

---
 Sources/ContainerLog/FileLogHandler.swift   |  5 ++++-
 Sources/ContainerLog/OSLogHandler.swift     | 21 ++++++++-------------
 Sources/ContainerLog/StderrLogHandler.swift | 17 +++++++++++++----
 3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/Sources/ContainerLog/FileLogHandler.swift b/Sources/ContainerLog/FileLogHandler.swift
index 446fa3308..5aa7d318c 100644
--- a/Sources/ContainerLog/FileLogHandler.swift
+++ b/Sources/ContainerLog/FileLogHandler.swift
@@ -23,6 +23,7 @@ import SystemPackage
 public struct FileLogHandler: LogHandler {
     public var logLevel: Logger.Level = .info
     public var metadata: Logger.Metadata = [:]
+    public var metadataProvider: Logger.MetadataProvider?
 
     private let label: String
     private let category: String
@@ -76,8 +77,10 @@ public struct FileLogHandler: LogHandler {
         }()
         let timestamp = timestampFormatter.string(from: Date())
 
-        // Merge logger-level metadata with per-message metadata
         var effectiveMetadata = self.metadata
+        if let provided = self.metadataProvider?.get(), !provided.isEmpty {
+            effectiveMetadata.merge(provided) { _, new in new }
+        }
         if let metadata {
             effectiveMetadata.merge(metadata) { _, new in new }
         }
diff --git a/Sources/ContainerLog/OSLogHandler.swift b/Sources/ContainerLog/OSLogHandler.swift
index 227e35e03..2e8cfe11d 100644
--- a/Sources/ContainerLog/OSLogHandler.swift
+++ b/Sources/ContainerLog/OSLogHandler.swift
@@ -24,13 +24,8 @@ public struct OSLogHandler: LogHandler {
     private let logger: os.Logger
 
     public var logLevel: Logger.Level = .info
-    private var formattedMetadata: String?
-
-    public var metadata = Logger.Metadata() {
-        didSet {
-            self.formattedMetadata = self.formatMetadata(self.metadata)
-        }
-    }
+    public var metadataProvider: Logger.MetadataProvider?
+    public var metadata = Logger.Metadata()
 
     public subscript(metadataKey metadataKey: String) -> Logger.Metadata.Value? {
         get {
@@ -56,14 +51,14 @@ extension OSLogHandler {
         function: String,
         line: UInt
     ) {
-        var formattedMetadata = self.formattedMetadata
+        var effectiveMetadata = self.metadata
+        if let provided = self.metadataProvider?.get(), !provided.isEmpty {
+            effectiveMetadata.merge(provided) { _, new in new }
+        }
         if let metadataOverride = metadata, !metadataOverride.isEmpty {
-            formattedMetadata = self.formatMetadata(
-                self.metadata.merging(metadataOverride) {
-                    $1
-                }
-            )
+            effectiveMetadata.merge(metadataOverride) { _, new in new }
         }
+        let formattedMetadata = self.formatMetadata(effectiveMetadata)
 
         var finalMessage = message.description
         if let formattedMetadata {
diff --git a/Sources/ContainerLog/StderrLogHandler.swift b/Sources/ContainerLog/StderrLogHandler.swift
index ffcd9179e..7dbbfe8d6 100644
--- a/Sources/ContainerLog/StderrLogHandler.swift
+++ b/Sources/ContainerLog/StderrLogHandler.swift
@@ -22,6 +22,7 @@ import Logging
 public struct StderrLogHandler: LogHandler {
     public var logLevel: Logger.Level = .info
     public var metadata: Logger.Metadata = [:]
+    public var metadataProvider: Logger.MetadataProvider?
 
     public subscript(metadataKey metadataKey: String) -> Logger.Metadata.Value? {
         get {
@@ -43,13 +44,21 @@ public struct StderrLogHandler: LogHandler {
         function: String,
         line: UInt
     ) {
+        var effectiveMetadata = self.metadata
+        if let provided = self.metadataProvider?.get(), !provided.isEmpty {
+            effectiveMetadata.merge(provided) { _, new in new }
+        }
+        if let metadata, !metadata.isEmpty {
+            effectiveMetadata.merge(metadata) { _, new in new }
+        }
+
         let data: Data
         switch logLevel {
         case .debug, .trace:
             let timestamp = isoTimestamp()
-            if let metadata, !metadata.isEmpty {
+            if !effectiveMetadata.isEmpty {
                 data =
-                    "\(timestamp) \(message.description): \(metadata.description)\n"
+                    "\(timestamp) \(message.description): \(effectiveMetadata.description)\n"
                     .data(using: .utf8) ?? Data()
             } else {
                 data =
@@ -57,9 +66,9 @@ public struct StderrLogHandler: LogHandler {
                     .data(using: .utf8) ?? Data()
             }
         default:
-            if let metadata, !metadata.isEmpty {
+            if !effectiveMetadata.isEmpty {
                 data =
-                    "\(message.description): \(metadata.description)\n"
+                    "\(message.description): \(effectiveMetadata.description)\n"
                     .data(using: .utf8) ?? Data()
             } else {
                 data =