jextract: add support for desugared optional on Android 23 (#498)

Author: madsodgaard

Sources/SwiftJava/AndroidSupport.swift

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+public enum AndroidSupport {
+  /// Performs any known name conversions
+  /// for types that are desugared on specific Android versions
+  public static func androidDesugarClassNameConversion(
+    for fullClassName: String
+  ) -> String {
+#if os(Android) && compiler(>=6.3)
+    switch fullClassName {
+    case "java.util.Optional":
+      // On API 23, Optionals are desugared
+      if #unavailable(Android 24) {
+        return "j$.util.Optional"
+      }
+
+    default:
+      break
+    }
+#endif
+    return fullClassName
+  }
+}

Sources/SwiftJavaMacros/JavaClassMacro.swift

@@ -79,7 +79,7 @@ extension JavaClassMacro: MemberMacro {
     }
 
     var members: [DeclSyntax] = []
-
+    
     // Determine the modifiers to use for the fullJavaClassName member.
     let fullJavaClassNameMemberModifiers: String
     switch (isSwiftClass, isJavaLangObject) {
@@ -94,7 +94,13 @@ extension JavaClassMacro: MemberMacro {
     let classNameAccessSpecifier = isSwiftClass ? "open" : "public"
     members.append("""
       /// The full Java class name for this Swift type.
-      \(raw: classNameAccessSpecifier) \(raw: fullJavaClassNameMemberModifiers) var fullJavaClassName: String { \(literal: className) }
+      \(raw: classNameAccessSpecifier) \(raw: fullJavaClassNameMemberModifiers) var fullJavaClassName: String {
+        #if os(Android)
+          AndroidSupport.androidDesugarClassNameConversion(for: "\(raw: className)")
+        #else
+          "\(raw: className)"
+        #endif
+      }
       """
     )
 

Tests/SwiftJavaMacrosTests/JavaClassMacroTests.swift

@@ -43,7 +43,11 @@ class JavaKitMacroTests: XCTestCase {
       
             /// The full Java class name for this Swift type.
             open override class var fullJavaClassName: String {
+              #if os(Android)
+                AndroidSupport.androidDesugarClassNameConversion(for: "org.swift.example.HelloWorld")
+              #else
                 "org.swift.example.HelloWorld"
+              #endif
             }
       
             public required init(javaHolder: JavaObjectHolder) {
@@ -150,7 +154,11 @@ class JavaKitMacroTests: XCTestCase {
       
             /// The full Java class name for this Swift type.
             public static var fullJavaClassName: String {
+              #if os(Android)
+                AndroidSupport.androidDesugarClassNameConversion(for: "org.swift.example.HelloWorld")
+              #else
                 "org.swift.example.HelloWorld"
+              #endif
             }
 
             public typealias JavaSuperclass = JavaObject
@@ -242,7 +250,11 @@ class JavaKitMacroTests: XCTestCase {
 
             /// The full Java class name for this Swift type.
             open override class var fullJavaClassName: String {
+              #if os(Android)
+                AndroidSupport.androidDesugarClassNameConversion(for: "org.swift.example.HelloWorld")
+              #else
                 "org.swift.example.HelloWorld"
+              #endif
             }
 
             public required init(javaHolder: JavaObjectHolder) {
@@ -283,7 +295,11 @@ class JavaKitMacroTests: XCTestCase {
 
             /// The full Java class name for this Swift type.
             open class var fullJavaClassName: String {
+              #if os(Android)
+                AndroidSupport.androidDesugarClassNameConversion(for: "java.lang.Object")
+              #else
                 "java.lang.Object"
+              #endif
             }
 
             public var javaHolder: JavaObjectHolder
@@ -319,7 +335,11 @@ class JavaKitMacroTests: XCTestCase {
 
             /// The full Java class name for this Swift type.
             open override class var fullJavaClassName: String {
+              #if os(Android)
+                AndroidSupport.androidDesugarClassNameConversion(for: "java.lang.Optional")
+              #else
                 "java.lang.Optional"
+              #endif
             }
 
             public required init(javaHolder: JavaObjectHolder) {