Add macros to 5.9 tools-version (#6472)

SE-0394 has been accepted, so we're making macros available as part of the 5.9 tools-version.

Author: neonichu

Sources/CompilerPluginSupport/TargetExtensions.swift

@@ -13,7 +13,7 @@
 @_spi(PackageDescriptionInternal) import PackageDescription
 
 public extension Target {
-    @available(_PackageDescription, introduced: 999.0)
+    @available(_PackageDescription, introduced: 5.9)
     static func macro(
         name: String,
         dependencies: [Dependency] = [],

Sources/Workspace/InitPackage.swift

@@ -342,8 +342,7 @@ public final class InitPackage {
         // Create a tools version with current version but with patch set to zero.
         // We do this to avoid adding unnecessary constraints to patch versions, if
         // the package really needs it, they should add it manually.
-        let version = packageType == .macro ? ToolsVersion.vNext
-            : InitPackage.newPackageToolsVersion.zeroedPatch
+        let version = InitPackage.newPackageToolsVersion.zeroedPatch
 
         // Write the current tools version.
         try ToolsVersionSpecificationWriter.rewriteSpecification(

Tests/PackageLoadingTests/PD_5_9_LoadingTests.swift

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Basics
+import PackageLoading
+import PackageModel
+import SPMTestSupport
+import XCTest
+
+class PackageDescription5_9LoadingTests: PackageDescriptionLoadingTests {
+    override var toolsVersion: ToolsVersion {
+        .v5_9
+    }
+
+    func testMacroTargets() throws {
+        let content = """
+            import CompilerPluginSupport
+            import PackageDescription
+
+            let package = Package(name: "MyPackage",
+                targets: [
+                    .macro(name: "MyMacro", swiftSettings: [.define("BEST")], linkerSettings: [.linkedLibrary("best")]),
+                ]
+            )
+            """
+
+        let observability = ObservabilitySystem.makeForTesting()
+        let (_, diagnostics) = try loadAndValidateManifest(content, observabilityScope: observability.topScope)
+        XCTAssertEqual(diagnostics.count, 0, "unexpected diagnostics: \(diagnostics)")
+    }
+}

Tests/PackageLoadingTests/PD_Next_LoadingTests.swift

@@ -39,21 +39,4 @@ class PackageDescriptionNextLoadingTests: PackageDescriptionLoadingTests {
             }
         }
     }
-
-    func testMacroTargets() throws {
-        let content = """
-            import CompilerPluginSupport
-            import PackageDescription
-
-            let package = Package(name: "MyPackage",
-                targets: [
-                    .macro(name: "MyMacro", swiftSettings: [.define("BEST")], linkerSettings: [.linkedLibrary("best")]),
-                ]
-            )
-            """
-
-        let observability = ObservabilitySystem.makeForTesting()
-        let (_, diagnostics) = try loadAndValidateManifest(content, observabilityScope: observability.topScope)
-        XCTAssertEqual(diagnostics.count, 0, "unexpected diagnostics: \(diagnostics)")
-    }
 }