[SLG-0002] Implementation: Compile-time log level elimination using traits

.github/workflows/main.yml

@@ -31,13 +31,20 @@ jobs:
       windows_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
 
   benchmarks:
-    name: Benchmarks
+    name: Benchmarks (NoTraits)
     uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
     with:
-      benchmark_package_path: "Benchmarks"
+      benchmark_package_path: "Benchmarks/NoTraits"
       macos_xcode_16_4_enabled: true
       macos_xcode_26_1_enabled: true
 
+  benchmarks-MaxLogLevelWarningBenchmarks-trait:
+    name: Benchmarks (MaxLogLevelWarning)
+    uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
+    with:
+      benchmark_package_path: "Benchmarks/MaxLogLevelWarning"
+      macos_xcode_26_1_enabled: true
+
   cxx-interop:
     name: Cxx interop
     uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main

.github/workflows/pull_request.yml

@@ -35,14 +35,22 @@ jobs:
       windows_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
 
   benchmarks:
-    name: Benchmarks
+    name: Benchmarks (NoTraits)
     uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
     with:
-      benchmark_package_path: "Benchmarks"
+      benchmark_package_path: "Benchmarks/NoTraits"
       macos_runner_pool: general
       macos_xcode_16_4_enabled: true
       macos_xcode_26_1_enabled: true
 
+  benchmarks-MaxLogLevelWarningBenchmarks-trait:
+    name: Benchmarks (MaxLogLevelWarning)
+    uses: apple/swift-nio/.github/workflows/benchmarks.yml@main
+    with:
+      benchmark_package_path: "Benchmarks/MaxLogLevelWarning"
+      macos_runner_pool: general
+      macos_xcode_26_1_enabled: true
+
   cxx-interop:
     name: Cxx interop
     uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main

.licenseignore

@@ -19,6 +19,8 @@ Package.swift
 **/Package.swift
 Package@-*.swift
 **/Package@-*.swift
+Package@swift-*.swift
+**/Package@swift-*.swift
 Package.resolved
 **/Package.resolved
 Makefile

Benchmarks/MaxLogLevelWarning/.gitignore

@@ -0,0 +1,8 @@
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc

Benchmarks/MaxLogLevelWarning/Benchmarks/MaxLogLevelWarningBenchmarks/MaxLogLevelWarning.swift

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Logging API open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift Logging API project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift Logging API project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Benchmark
+import BenchmarksFactory
+import Foundation
+import Logging
+
+public let benchmarks: @Sendable () -> Void = {
+    makeBenchmark(loggerLevel: .notice, logLevel: .notice) { logger in
+        logger.notice("hello, benchmarking world")
+    }
+    makeBenchmark(loggerLevel: .notice, logLevel: .notice, "_generic") { logger in
+        logger.log(level: .notice, "hello, benchmarking world")
+    }
+    makeBenchmark(loggerLevel: .warning, logLevel: .warning) { logger in
+        logger.warning("hello, benchmarking world")
+    }
+    makeBenchmark(loggerLevel: .warning, logLevel: .warning, "_generic") { logger in
+        logger.log(level: .warning, "hello, benchmarking world")
+    }
+}

Benchmarks/MaxLogLevelWarning/Package.swift

@@ -0,0 +1,38 @@
+// swift-tools-version: 6.1
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "MaxLogLevelWarning",
+    platforms: [
+        .macOS(.v13)
+    ],
+    products: [
+        .executable(name: "MaxLogLevelWarning", targets: ["MaxLogLevelWarning"])
+    ],
+    dependencies: [
+        // swift-log
+        .package(
+            path: "../../",
+            traits: ["MaxLogLevelWarning"]
+        ),
+        // Parent Benchmarks
+        .package(name: "Benchmarks", path: "../"),
+        .package(url: "https://github.com/ordo-one/package-benchmark.git", from: "1.29.6"),
+    ],
+    targets: [
+        .executableTarget(
+            name: "MaxLogLevelWarning",
+            dependencies: [
+                .product(name: "BenchmarksFactory", package: "Benchmarks"),
+                .product(name: "Benchmark", package: "package-benchmark"),
+                .product(name: "Logging", package: "swift-log"),
+            ],
+            path: "Benchmarks/MaxLogLevelWarningBenchmarks",
+            plugins: [
+                .plugin(name: "BenchmarkPlugin", package: "package-benchmark")
+            ]
+        )
+    ]
+)

Benchmarks/Thresholds/Xcode 26.1/SwiftLogBenchmarks.debug_log_with_error_log_level.p90.json → Benchmarks/MaxLogLevelWarning/Thresholds/Xcode 26.1/MaxLogLevelWarning.notice_log_with_notice_log_level.p90.json

@@ -1,4 +1,4 @@
 {
-  "instructions" : 1045,
+  "instructions" : 589,
   "objectAllocCount" : 0
 }

Benchmarks/Thresholds/Xcode 16.4/SwiftLogBenchmarks.debug_log_with_error_log_level.p90.json → Benchmarks/MaxLogLevelWarning/Thresholds/Xcode 26.1/MaxLogLevelWarning.notice_log_with_notice_log_level_generic.p90.json

@@ -1,4 +1,4 @@
 {
-  "instructions" : 1126,
+  "instructions" : 589,
   "objectAllocCount" : 0
 }

Benchmarks/Thresholds/Xcode 16.4/SwiftLogBenchmarks.error_log_with_error_log_level.p90.json → Benchmarks/MaxLogLevelWarning/Thresholds/Xcode 26.1/MaxLogLevelWarning.warning_log_with_warning_log_level.p90.json

@@ -1,4 +1,4 @@
 {
-  "instructions" : 3279,
+  "instructions" : 3009,
   "objectAllocCount" : 1
 }

Benchmarks/Thresholds/Xcode 16.4/SwiftLogBenchmarks.debug_log_with_debug_log_level.p90.json → Benchmarks/MaxLogLevelWarning/Thresholds/Xcode 26.1/MaxLogLevelWarning.warning_log_with_warning_log_level_generic.p90.json

@@ -1,4 +1,4 @@
 {
-  "instructions" : 3279,
+  "instructions" : 3009,
   "objectAllocCount" : 1
 }

Benchmarks/NoTraits/.gitignore

@@ -0,0 +1,8 @@
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc

Benchmarks/NoTraits/Benchmarks/NoTraitsBenchmarks/NoTraits.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Logging API open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift Logging API project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift Logging API project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Benchmark
+import BenchmarksFactory
+import Foundation
+import Logging
+
+public let benchmarks: @Sendable () -> Void = {
+    makeBenchmark(loggerLevel: .error, logLevel: .error, "_generic") { logger in
+        logger.log(level: .error, "hello, benchmarking world")
+    }
+    makeBenchmark(loggerLevel: .error, logLevel: .debug, "_generic") { logger in
+        logger.log(level: .debug, "hello, benchmarking world")
+    }
+}

Benchmarks/NoTraits/Package.swift

@@ -0,0 +1,37 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "NoTraits",
+    platforms: [
+        .macOS(.v13)
+    ],
+    products: [
+        .executable(name: "NoTraits", targets: ["NoTraits"])
+    ],
+    dependencies: [
+        // swift-log
+        .package(
+            path: "../../"
+        ),
+        // Parent Benchmarks
+        .package(name: "Benchmarks", path: "../"),
+        .package(url: "https://github.com/ordo-one/package-benchmark.git", from: "1.29.6"),
+    ],
+    targets: [
+        .executableTarget(
+            name: "NoTraits",
+            dependencies: [
+                .product(name: "BenchmarksFactory", package: "Benchmarks"),
+                .product(name: "Benchmark", package: "package-benchmark"),
+                .product(name: "Logging", package: "swift-log"),
+            ],
+            path: "Benchmarks/NoTraitsBenchmarks",
+            plugins: [
+                .plugin(name: "BenchmarkPlugin", package: "package-benchmark")
+            ]
+        )
+    ]
+)

Benchmarks/NoTraits/Thresholds/Xcode 16.4/NoTraits.debug_log_with_error_log_level_generic.p90.json

@@ -0,0 +1,4 @@
+{
+  "instructions" : 937,
+  "objectAllocCount" : 0
+}

Benchmarks/NoTraits/Thresholds/Xcode 16.4/NoTraits.error_log_with_error_log_level_generic.p90.json

@@ -0,0 +1,4 @@
+{
+  "instructions" : 1718,
+  "objectAllocCount" : 0
+}

Benchmarks/NoTraits/Thresholds/Xcode 26.1/NoTraits.debug_log_with_error_log_level_generic.p90.json

@@ -0,0 +1,4 @@
+{
+  "instructions" : 855,
+  "objectAllocCount" : 0
+}

Benchmarks/NoTraits/Thresholds/Xcode 26.1/NoTraits.error_log_with_error_log_level_generic.p90.json

@@ -0,0 +1,4 @@
+{
+  "instructions" : 1636,
+  "objectAllocCount" : 0
+}

Benchmarks/Package.swift

@@ -1,30 +1,27 @@
-// swift-tools-version: 6.0
+// swift-tools-version: 6.1
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
 
 let package = Package(
-    name: "Benchmarks",
+    name: "BenchmarksFactory",
     platforms: [
         .macOS(.v13)
     ],
+    products: [
+        .library(name: "BenchmarksFactory", targets: ["BenchmarksFactory"])
+    ],
     dependencies: [
-        .package(path: "../"),
         .package(url: "https://github.com/ordo-one/package-benchmark.git", from: "1.29.6"),
+        .package(path: "../"),  // swift-log
+    ],
+    targets: [
+        .target(
+            name: "BenchmarksFactory",
+            dependencies: [
+                .product(name: "Benchmark", package: "package-benchmark"),
+                .product(name: "Logging", package: "swift-log"),
+            ]
+        )
     ]
 )
-
-// Benchmark of SwiftLogBenchmarks
-package.targets += [
-    .executableTarget(
-        name: "SwiftLogBenchmarks",
-        dependencies: [
-            .product(name: "Benchmark", package: "package-benchmark"),
-            .product(name: "Logging", package: "swift-log"),
-        ],
-        path: "Benchmarks/SwiftLogBenchmarks",
-        plugins: [
-            .plugin(name: "BenchmarkPlugin", package: "package-benchmark")
-        ]
-    )
-]