Verify generated code compiles across Swift language modes

Package.swift

@@ -50,5 +50,49 @@ let package = Package(
             name: "ThemeKitGeneratorTests",
             dependencies: ["ThemeKitGenerator"]
         ),
+        .plugin(
+            name: "GenerateTestFixturesPlugin",
+            capability: .buildTool(),
+            dependencies: ["ThemeKitGeneratorCLI"],
+            path: "Plugins/GenerateTestFixturesPlugin"
+        ),
+        // Generated code compilation verification targets
+        .target(
+            name: "GeneratedCodeSwift5",
+            dependencies: ["ThemeKit"],
+            path: "Tests/GeneratedCodeSwift5",
+            swiftSettings: [.swiftLanguageMode(.v5)],
+            plugins: [.plugin(name: "GenerateTestFixturesPlugin")]
+        ),
+        .target(
+            name: "GeneratedCodeSwift5MainActor",
+            dependencies: ["ThemeKit"],
+            path: "Tests/GeneratedCodeSwift5MainActor",
+            swiftSettings: [.swiftLanguageMode(.v5), .defaultIsolation(MainActor.self)],
+            plugins: [.plugin(name: "GenerateTestFixturesPlugin")]
+        ),
+        .target(
+            name: "GeneratedCodeSwift6",
+            dependencies: ["ThemeKit"],
+            path: "Tests/GeneratedCodeSwift6",
+            swiftSettings: [.swiftLanguageMode(.v6)],
+            plugins: [.plugin(name: "GenerateTestFixturesPlugin")]
+        ),
+        .target(
+            name: "GeneratedCodeSwift6MainActor",
+            dependencies: ["ThemeKit"],
+            path: "Tests/GeneratedCodeSwift6MainActor",
+            swiftSettings: [.swiftLanguageMode(.v6), .defaultIsolation(MainActor.self)],
+            plugins: [.plugin(name: "GenerateTestFixturesPlugin")]
+        ),
+        .testTarget(
+            name: "GeneratedCodeCompilationTests",
+            dependencies: [
+                "GeneratedCodeSwift5",
+                "GeneratedCodeSwift5MainActor",
+                "GeneratedCodeSwift6",
+                "GeneratedCodeSwift6MainActor",
+            ]
+        ),
     ]
 )

Plugins/GenerateTestFixturesPlugin/GenerateTestFixturesPlugin.swift

@@ -0,0 +1,80 @@
+import PackagePlugin
+import Foundation
+
+@main
+struct GenerateTestFixturesPlugin: BuildToolPlugin {
+    func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] {
+        guard let sourceModule = target as? SourceModuleTarget else { return [] }
+
+        let configFile = sourceModule.sourceFiles.first { $0.url.lastPathComponent == "theme.json" }
+        guard let configFile else {
+            Diagnostics.error("No theme.json found in target \(target.name)")
+            return []
+        }
+
+        let tool = try context.tool(named: "ThemeKitGeneratorCLI")
+        let outputDir = context.pluginWorkDirectoryURL
+        let outputFiles = try computeOutputFiles(configURL: configFile.url, outputDir: outputDir)
+
+        return [
+            .buildCommand(
+                displayName: "Generate ThemeKit fixtures for \(target.name)",
+                executable: tool.url,
+                arguments: [
+                    "--config", configFile.url.path(),
+                    "--output", outputDir.path(),
+                    "--skip-defaults",
+                ],
+                inputFiles: [configFile.url],
+                outputFiles: outputFiles
+            ),
+        ]
+    }
+
+    /// Parses theme.json minimally to compute the list of files the generator will produce.
+    private func computeOutputFiles(configURL: URL, outputDir: URL) throws -> [URL] {
+        let data = try Data(contentsOf: configURL)
+        let json = try JSONSerialization.jsonObject(with: data) as? [String: Any] ?? [:]
+        let styles = json["styles"] as? [String: Any] ?? [:]
+        let config = json["config"] as? [String: Any] ?? [:]
+
+        let categoryKeys = styles.keys
+        let shouldGeneratePreview = config["shouldGeneratePreview"] as? Bool ?? false
+
+        // Map JSON category keys to struct names
+        let categoryStructNames: [String: String] = [
+            "colors": "ThemeColors",
+            "gradients": "ThemeGradients",
+            "meshGradients": "ThemeMeshGradients",
+            "shadows": "ThemeShadows",
+        ]
+
+        var files: [String] = []
+
+        // Static files (always generated)
+        files.append("ThemeShapeStyle.swift")
+        files.append("Environment+Theme.swift")
+        files.append("Theme.swift")
+        files.append("Theme+CopyWith.swift")
+
+        // Conditional: ThemeShadowedStyle only when shadows present
+        if categoryKeys.contains("shadows") {
+            files.append("ThemeShadowedStyle.swift")
+        }
+
+        // Per-category files
+        for key in categoryKeys {
+            guard let structName = categoryStructNames[key] else { continue }
+            files.append("\(structName).swift")
+            files.append("\(structName)+CopyWith.swift")
+            files.append("ShapeStyle+\(structName).swift")
+        }
+
+        // Optional preview file
+        if shouldGeneratePreview {
+            files.append("Theme+Preview.swift")
+        }
+
+        return files.map { outputDir.appendingPathComponent($0) }
+    }
+}

Sources/ThemeKitGeneratorCLI/main.swift

@@ -6,6 +6,7 @@ func run() throws {
 
     var configPath = "theme.json"
     var outputPath = "."
+    var skipDefaults = false
 
     var i = 1
     while i < args.count {
@@ -22,6 +23,8 @@ func run() throws {
                 throw GeneratorError.missingArgument("--output")
             }
             outputPath = args[i]
+        case "--skip-defaults":
+            skipDefaults = true
         default:
             break
         }
@@ -42,13 +45,15 @@ func run() throws {
 
     try FileManager.default.createDirectory(at: finalOutputURL, withIntermediateDirectories: true)
 
-    for file in result.files {
+    let filesToWrite = skipDefaults ? result.files.filter { $0.name != "Theme+Defaults.swift" } : result.files
+
+    for file in filesToWrite {
         let fileURL = finalOutputURL.appendingPathComponent(file.name)
         try file.content.write(to: fileURL, atomically: true, encoding: .utf8)
     }
 
-    print("ThemeKit: Generated \(result.files.count) files in \(finalOutputURL.path):")
-    for file in result.files {
+    print("ThemeKit: Generated \(filesToWrite.count) files in \(finalOutputURL.path):")
+    for file in filesToWrite {
         print("  - \(file.name)")
     }
 }

Tests/GeneratedCodeCompilationTests/GeneratedCodeCompilationTests.swift

@@ -0,0 +1,47 @@
+import Testing
+import GeneratedCodeSwift5
+import GeneratedCodeSwift5MainActor
+import GeneratedCodeSwift6
+import GeneratedCodeSwift6MainActor
+
+/// Verifies that ThemeKit-generated code compiles under all 4 combinations
+/// of Swift language mode (5/6) and default actor isolation (nonisolated/MainActor).
+///
+/// The primary verification is compilation itself — if these targets build, the
+/// generated code is compatible with that configuration. The tests below perform
+/// minimal runtime checks to confirm the types are usable.
+@Suite("Generated Code Compilation")
+struct GeneratedCodeCompilationTests {
+
+    @Test func swift5_typesAreUsable() {
+        let theme = GeneratedCodeSwift5.Theme.default
+        _ = theme.colors.surface
+        _ = theme.gradients.primary
+        _ = theme.meshGradients.aurora
+        _ = theme.shadows.card
+    }
+
+    @Test func swift5MainActor_typesAreUsable() {
+        let theme = GeneratedCodeSwift5MainActor.Theme.default
+        _ = theme.colors.surface
+        _ = theme.gradients.primary
+        _ = theme.meshGradients.aurora
+        _ = theme.shadows.card
+    }
+
+    @Test func swift6_typesAreUsable() {
+        let theme = GeneratedCodeSwift6.Theme.default
+        _ = theme.colors.surface
+        _ = theme.gradients.primary
+        _ = theme.meshGradients.aurora
+        _ = theme.shadows.card
+    }
+
+    @Test func swift6MainActor_typesAreUsable() {
+        let theme = GeneratedCodeSwift6MainActor.Theme.default
+        _ = theme.colors.surface
+        _ = theme.gradients.primary
+        _ = theme.meshGradients.aurora
+        _ = theme.shadows.card
+    }
+}

Tests/GeneratedCodeSwift5/Theme+Defaults.swift

@@ -0,0 +1,57 @@
+import SwiftUI
+import ThemeKit
+
+nonisolated extension Theme {
+    public static let `default` = Theme(
+        colors: .`default`,
+        gradients: .`default`,
+        meshGradients: .`default`,
+        shadows: .`default`
+    )
+}
+
+// MARK: - ThemeColors
+
+nonisolated extension ThemeColors {
+    public static let `default` = ThemeColors(
+        surface: .init(light: Color(red: 1, green: 1, blue: 1), dark: Color(red: 0, green: 0, blue: 0)),
+        primary: .init(light: Color(red: 0, green: 0.5, blue: 1), dark: Color(red: 0, green: 0.8, blue: 1))
+    )
+}
+
+// MARK: - ThemeGradients
+
+nonisolated extension ThemeGradients {
+    public static let `default` = ThemeGradients(
+        primary: .init(
+            light: .init(colors: [Color(red: 0, green: 0.5, blue: 1), Color(red: 0.5, green: 0, blue: 1)]),
+            dark:  .init(colors: [Color(red: 0, green: 0.8, blue: 1), Color(red: 0.3, green: 0, blue: 0.5)])
+        )
+    )
+}
+
+// MARK: - ThemeMeshGradients
+
+nonisolated extension ThemeMeshGradients {
+    public static let `default` = ThemeMeshGradients(
+        aurora: .init(
+            light: .init(width: 2, height: 2, colors: [
+                Color(red: 0, green: 0.5, blue: 1), Color(red: 0.5, green: 0, blue: 1),
+                Color(red: 0, green: 0.8, blue: 0.8), Color(red: 0, green: 0.8, blue: 0.3),
+            ]),
+            dark: .init(width: 2, height: 2, colors: [
+                Color(red: 0.3, green: 0, blue: 0.5), Color(red: 0.5, green: 0, blue: 1),
+                Color(red: 0, green: 0.5, blue: 0.5), Color(red: 0, green: 0.7, blue: 0.5),
+            ])
+        )
+    )
+}
+
+// MARK: - ThemeShadows
+
+nonisolated extension ThemeShadows {
+    public static let `default` = ThemeShadows(
+        card:  .init(light: .drop(radius: 4), dark: .drop(radius: 4)),
+        inner: .init(light: .inner(radius: 2), dark: .inner(radius: 2))
+    )
+}

Tests/GeneratedCodeSwift5/theme.json

@@ -0,0 +1,12 @@
+{
+    "styles": {
+        "colors": ["surface", {"name": "primary", "style": "primaryColor"}],
+        "gradients": [{"name": "primary", "style": "primaryGradient"}],
+        "meshGradients": ["aurora"],
+        "shadows": ["card", {"name": "inner", "style": "innerGlow"}]
+    },
+    "config": {
+        "outputPath": ".",
+        "shouldGeneratePreview": true
+    }
+}

Tests/GeneratedCodeSwift5MainActor/Theme+Defaults.swift

@@ -0,0 +1,57 @@
+import SwiftUI
+import ThemeKit
+
+nonisolated extension Theme {
+    public static let `default` = Theme(
+        colors: .`default`,
+        gradients: .`default`,
+        meshGradients: .`default`,
+        shadows: .`default`
+    )
+}
+
+// MARK: - ThemeColors
+
+nonisolated extension ThemeColors {
+    public static let `default` = ThemeColors(
+        surface: .init(light: Color(red: 1, green: 1, blue: 1), dark: Color(red: 0, green: 0, blue: 0)),
+        primary: .init(light: Color(red: 0, green: 0.5, blue: 1), dark: Color(red: 0, green: 0.8, blue: 1))
+    )
+}
+
+// MARK: - ThemeGradients
+
+nonisolated extension ThemeGradients {
+    public static let `default` = ThemeGradients(
+        primary: .init(
+            light: .init(colors: [Color(red: 0, green: 0.5, blue: 1), Color(red: 0.5, green: 0, blue: 1)]),
+            dark:  .init(colors: [Color(red: 0, green: 0.8, blue: 1), Color(red: 0.3, green: 0, blue: 0.5)])
+        )
+    )
+}
+
+// MARK: - ThemeMeshGradients
+
+nonisolated extension ThemeMeshGradients {
+    public static let `default` = ThemeMeshGradients(
+        aurora: .init(
+            light: .init(width: 2, height: 2, colors: [
+                Color(red: 0, green: 0.5, blue: 1), Color(red: 0.5, green: 0, blue: 1),
+                Color(red: 0, green: 0.8, blue: 0.8), Color(red: 0, green: 0.8, blue: 0.3),
+            ]),
+            dark: .init(width: 2, height: 2, colors: [
+                Color(red: 0.3, green: 0, blue: 0.5), Color(red: 0.5, green: 0, blue: 1),
+                Color(red: 0, green: 0.5, blue: 0.5), Color(red: 0, green: 0.7, blue: 0.5),
+            ])
+        )
+    )
+}
+
+// MARK: - ThemeShadows
+
+nonisolated extension ThemeShadows {
+    public static let `default` = ThemeShadows(
+        card:  .init(light: .drop(radius: 4), dark: .drop(radius: 4)),
+        inner: .init(light: .inner(radius: 2), dark: .inner(radius: 2))
+    )
+}

Tests/GeneratedCodeSwift5MainActor/theme.json

@@ -0,0 +1,12 @@
+{
+    "styles": {
+        "colors": ["surface", {"name": "primary", "style": "primaryColor"}],
+        "gradients": [{"name": "primary", "style": "primaryGradient"}],
+        "meshGradients": ["aurora"],
+        "shadows": ["card", {"name": "inner", "style": "innerGlow"}]
+    },
+    "config": {
+        "outputPath": ".",
+        "shouldGeneratePreview": true
+    }
+}