Create new target for common code (#1331)

* Extract the SourceLanguage type to a new "Common" target

* Keep public type alias to moved SourceLanguage type

* Use Swift 6 language mode in new target

* Add "DocC" prefix to new common target

Author: d-ronnqvist

Package.swift

@@ -43,6 +43,7 @@ let package = Package(
         .target(
             name: "SwiftDocC",
             dependencies: [
+                .target(name: "DocCCommon"),
                 .product(name: "Markdown", package: "swift-markdown"),
                 .product(name: "SymbolKit", package: "swift-docc-symbolkit"),
                 .product(name: "CLMDB", package: "swift-lmdb"),
@@ -55,6 +56,7 @@ let package = Package(
             name: "SwiftDocCTests",
             dependencies: [
                 .target(name: "SwiftDocC"),
+                .target(name: "DocCCommon"),
                 .target(name: "SwiftDocCTestUtilities"),
             ],
             resources: [
@@ -70,6 +72,7 @@ let package = Package(
             name: "SwiftDocCUtilities",
             dependencies: [
                 .target(name: "SwiftDocC"),
+                .target(name: "DocCCommon"),
                 .product(name: "NIOHTTP1", package: "swift-nio", condition: .when(platforms: [.macOS, .iOS, .linux, .android])),
                 .product(name: "ArgumentParser", package: "swift-argument-parser")
             ],
@@ -81,6 +84,7 @@ let package = Package(
             dependencies: [
                 .target(name: "SwiftDocCUtilities"),
                 .target(name: "SwiftDocC"),
+                .target(name: "DocCCommon"),
                 .target(name: "SwiftDocCTestUtilities"),
             ],
             resources: [
@@ -95,6 +99,7 @@ let package = Package(
             name: "SwiftDocCTestUtilities",
             dependencies: [
                 .target(name: "SwiftDocC"),
+                .target(name: "DocCCommon"),
                 .product(name: "SymbolKit", package: "swift-docc-symbolkit"),
             ],
             swiftSettings: swiftSettings
@@ -109,6 +114,25 @@ let package = Package(
             exclude: ["CMakeLists.txt"],
             swiftSettings: swiftSettings
         ),
+        
+        // A few common types and core functionality that's useable by all other targets.
+        .target(
+            name: "DocCCommon",
+            dependencies: [
+                // This target shouldn't have any local dependencies so that all other targets can depend on it.
+                // We can add dependencies on SymbolKit and Markdown here but they're not needed yet.
+            ],
+            swiftSettings: [.swiftLanguageMode(.v6)]
+        ),
+        
+        .testTarget(
+            name: "DocCCommonTests",
+            dependencies: [
+                .target(name: "DocCCommon"),
+                .target(name: "SwiftDocCTestUtilities"),
+            ],
+            swiftSettings: [.swiftLanguageMode(.v6)]
+        ),
 
         // Test app for SwiftDocCUtilities
         .executableTarget(

Sources/SwiftDocCUtilities/CMakeLists.txt renamed to Sources/CommandLine/CMakeLists.txt

@@ -1,15 +1,15 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021-2023 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2025 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
 /// A programming language.
-public struct SourceLanguage: Hashable, Codable, Comparable {
+public struct SourceLanguage: Hashable, Codable, Comparable, Sendable {
     /// The display name of the programming language.
     public var name: String
     /// A globally unique identifier for the language.
@@ -132,7 +132,7 @@ public struct SourceLanguage: Hashable, Codable, Comparable {
     public static let metal = SourceLanguage(name: "Metal", id: "metal")
 
     /// The list of programming languages that are known to DocC.
-    public static var knownLanguages: [SourceLanguage] = [.swift, .objectiveC, .javaScript, .data, .metal]
+    public static let knownLanguages: [SourceLanguage] = [.swift, .objectiveC, .javaScript, .data, .metal]
 
     enum CodingKeys: CodingKey {
         case name
@@ -157,7 +157,9 @@ public struct SourceLanguage: Hashable, Codable, Comparable {
 
         try container.encode(self.name, forKey: SourceLanguage.CodingKeys.name)
         try container.encode(self.id, forKey: SourceLanguage.CodingKeys.id)
-        try container.encodeIfNotEmpty(self.idAliases, forKey: SourceLanguage.CodingKeys.idAliases)
+        if !self.idAliases.isEmpty {
+            try container.encode(self.idAliases, forKey: SourceLanguage.CodingKeys.idAliases)
+        }
         try container.encode(self.linkDisambiguationID, forKey: SourceLanguage.CodingKeys.linkDisambiguationID)
     }
 

Sources/SwiftDocC/Model/SourceLanguage.swift renamed to Sources/DocCCommon/SourceLanguage.swift

@@ -0,0 +1,13 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2025 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+ See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+public import DocCCommon
+
+public typealias SourceLanguage = DocCCommon.SourceLanguage

Sources/SwiftDocC/Utility/CommonTypeExports.swift

@@ -8,7 +8,7 @@
  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
-@testable import SwiftDocC
+import DocCCommon
 import XCTest
 
 class SourceLanguageTests: XCTestCase {