JavaKit: add source/target versions to Java2Swift.config

Fixes: #152

Author: lhoward

Plugins/JavaCompilerPlugin/JavaCompilerPlugin.swift

@@ -15,6 +15,30 @@
 import Foundation
 import PackagePlugin
 
+typealias JavaVersion = Int
+
+/// Note: there is a copy of this struct in the Java2Swift plugin. They
+/// must be kept in sync.
+struct Configuration: Codable {
+  var sourceCompatibility: JavaVersion?
+  var targetCompatibility: JavaVersion?
+}
+
+extension Configuration {
+  var compilerVersionArgs: [String] {
+    var compilerVersionArgs = [String]()
+
+    if let sourceCompatibility {
+      compilerVersionArgs += ["--source", String(sourceCompatibility)]
+    }
+    if let targetCompatibility {
+      compilerVersionArgs += ["--target", String(targetCompatibility)]
+    }
+
+    return compilerVersionArgs
+  }
+}
+
 @main
 struct JavaCompilerBuildToolPlugin: BuildToolPlugin {
   func createBuildCommands(context: PluginContext, target: Target) throws -> [Command] {
@@ -32,6 +56,13 @@ struct JavaCompilerBuildToolPlugin: BuildToolPlugin {
     // so we cannot eliminate this deprecation warning.
     let sourceDir = target.directory.string
 
+    // The name of the configuration file JavaKit.config from the target for
+    // which we are generating Swift wrappers for Java classes.
+    let configFile = URL(filePath: sourceDir)
+      .appending(path: "Java2Swift.config")
+    let configData = try Data(contentsOf: configFile)
+    let config = try JSONDecoder().decode(Configuration.self, from: configData)
+
     // The class files themselves will be generated into the build directory
     // for this target.
     let classFiles = javaFiles.map { sourceFileURL in
@@ -60,7 +91,7 @@ struct JavaCompilerBuildToolPlugin: BuildToolPlugin {
         arguments: javaFiles.map { $0.path(percentEncoded: false) } + [
           "-d", javaClassFileURL.path(),
           "-parameters", // keep parameter names, which allows us to emit them in generated Swift decls
-        ],
+        ] + config.compilerVersionArgs,
         inputFiles: javaFiles,
         outputFiles: classFiles
       )

Sources/Java2SwiftLib/Configuration.swift

@@ -12,6 +12,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+package typealias JavaVersion = Int
+
 /// Configuration for the Java2Swift translation tool, provided on a per-target
 /// basis.
 ///
@@ -26,8 +28,18 @@ package struct Configuration: Codable {
   /// the corresponding Swift names (e.g., JavaVector).
   package var classes: [String: String] = [:]
 
-  package init(classPath: String? = nil, classes: [String : String] = [:]) {
+  package var sourceCompatibility: JavaVersion?
+  package var targetCompatibility: JavaVersion?
+
+  package init(
+    classPath: String? = nil,
+    classes: [String : String] = [:],
+    sourceCompatibility: JavaVersion? = nil,
+    targetCompatibility: JavaVersion? = nil
+  ) {
     self.classPath = classPath
     self.classes = classes
+    self.sourceCompatibility = sourceCompatibility
+    self.targetCompatibility = targetCompatibility
   }
 }