Improve Optional handling, and generic get() -> T

Author: ktoso

Samples/JavaKitSampleApp/Package.swift

@@ -78,5 +78,16 @@ let package = Package(
         .plugin(name: "SwiftJavaPlugin", package: "swift-java"),
       ]
     ),
+    
+    .testTarget(
+      name: "JavaKitExampleTests",
+      dependencies: [
+        "JavaKitExample"
+      ],
+      swiftSettings: [
+        .swiftLanguageMode(.v5),
+        .unsafeFlags(["-I\(javaIncludePath)", "-I\(javaPlatformIncludePath)"])
+      ]
+    ),
   ]
 )

Samples/JavaKitSampleApp/Sources/JavaKitExample/com/example/swift/ThreadSafeHelperClass.java

@@ -23,14 +23,28 @@
 public class ThreadSafeHelperClass {
     public ThreadSafeHelperClass() { }
 
-    public Optional<String> text = Optional.of("");
+    public Optional<String> text = Optional.of("cool string");
 
     public final OptionalDouble val = OptionalDouble.of(2);
 
     public String getValue(Optional<String> name) {
         return name.orElse("");
     }
 
+
+    public String getOrElse(Optional<String> name) {
+        return name.orElse("or else value");
+    }
+
+    public Optional<String> getNil() {
+        return Optional.empty();
+    }
+
+    // @NonNull
+    // public Optional<String> getNil() {
+    //     return Optional.empty();
+    // }
+
     public Optional<String> getText() {
         return text;
     }

Samples/JavaKitSampleApp/Tests/JavaKitExampleTests/JavaKitOptionalTests.swift

@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 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
+//
+//===----------------------------------------------------------------------===//
+
+import JavaKitExample
+
+import SwiftJava
+import JavaUtilFunction
+import Testing
+
+@Suite
+struct ManglingTests {
+
+  @Test
+  func methodMangling() throws {
+    let jvm = try! JavaVirtualMachine.shared(
+      classpath: [
+        ".build/plugins/outputs/javakitsampleapp/JavaKitExample/destination/JavaCompilerPlugin/Java"
+      ]
+    )
+    let env = try! jvm.environment()
+
+    let helper = ThreadSafeHelperClass(environment: env)
+    
+    let text: JavaString? = helper.textOptional
+    #expect(#"Optional("cool string")"# == String(describing: Optional("cool string")))
+    #expect(#"Optional("cool string")"# == String(describing: text))
+
+    // let defaultValue: String? = helper.getOrElse(JavaOptional<JavaString>.empty())
+    // #expect(#"Optional("or else value")"# == String(describing: defaultValue))
+    
+    let noneValue: JavaOptional<JavaString> = helper.getNil()!
+    #expect(noneValue.isPresent() == false)
+    #expect("\(noneValue)" == "SwiftJava.JavaOptional<SwiftJava.JavaString>")
+    
+    let textFunc: JavaString? = helper.getTextOptional()
+    #expect(#"Optional("cool string")"# == String(describing: textFunc))
+    
+    let doubleOpt: Double? = helper.valOptional
+    #expect(#"Optional(2.0)"# == String(describing: doubleOpt))
+    
+    let longOpt: Int64? = helper.fromOptional(21 as Int32?)
+    #expect(#"Optional(21)"# == String(describing: longOpt))
+  }
+
+}

Samples/JavaKitSampleApp/ci-validate.sh

@@ -3,7 +3,9 @@
 set -e
 set -x
 
-swift build
+swift build \
+  --disable-experimental-prebuilts  # FIXME: until prebuilt swift-syntax isn't broken on 6.2 anymore: https://github.com/swiftlang/swift-java/issues/418
+
 "$JAVA_HOME/bin/java" \
     -cp .build/plugins/outputs/javakitsampleapp/JavaKitExample/destination/JavaCompilerPlugin/Java \
     -Djava.library.path=.build/debug \

Sources/SwiftJava/AnyJavaObject.swift

@@ -59,7 +59,11 @@ public protocol AnyJavaObjectWithCustomClassLoader: AnyJavaObject {
 extension AnyJavaObject {
   /// Retrieve the underlying Java object.
   public var javaThis: jobject {
-    javaHolder.object!
+    javaHolder.object! // FIXME: this is a bad idea, can be null
+  }
+  
+  public var javaThisOptional: jobject? {
+    javaHolder.object
   }
 
   /// Retrieve the environment in which this Java object resides.

Sources/SwiftJava/JavaObject+Inheritance.swift

@@ -22,16 +22,16 @@ extension AnyJavaObject {
   private func isInstanceOf<OtherClass: AnyJavaObject>(
     _ otherClass: OtherClass.Type
   ) -> jclass? {
-    try? otherClass.withJNIClass(in: javaEnvironment) { otherJavaClass in
-      if javaEnvironment.interface.IsInstanceOf(
-       javaEnvironment,
-       javaThis,
-       otherJavaClass
-     ) == 0 {
-       return nil
-     }
+    guard let this: jobject = javaThisOptional else {
+      return nil 
+    }
+
+    return try? otherClass.withJNIClass(in: javaEnvironment) { otherJavaClass in
+      if javaEnvironment.interface.IsInstanceOf(javaEnvironment, this, otherJavaClass) == 0 { 
+        return nil
+      }
 
-     return otherJavaClass
+      return otherJavaClass
     }
   }
 

Sources/SwiftJava/JavaString+Extensions.swift

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 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
+//
+//===----------------------------------------------------------------------===//
+
+import CSwiftJavaJNI
+import JavaTypes
+
+extension JavaString: CustomStringConvertible, CustomDebugStringConvertible { 
+  public var description: String {
+    return toString()
+  }
+  public var debugDescription: String {
+    return "\"" + toString() + "\""
+  }
+}
+
+extension Optional where Wrapped == JavaString {
+  public var description: String {
+    switch self { 
+      case .some(let value): "Optional(\(value.toString())"
+      case .none: "nil"
+    }
+  }
+}

Sources/SwiftJava/Macros.swift

@@ -124,7 +124,9 @@ public macro JavaStaticField(_ javaFieldName: String? = nil, isFinal: Bool = fal
 ///
 /// corresponds to the Java constructor `HelloSwift(String name)`.
 @attached(body)
-public macro JavaMethod() = #externalMacro(module: "SwiftJavaMacros", type: "JavaMethodMacro")
+public macro JavaMethod(
+  genericResult: String? = nil
+) = #externalMacro(module: "SwiftJavaMacros", type: "JavaMethodMacro")
 
 /// Attached macro that turns a Swift method on JavaClass into one that wraps
 /// a Java static method on the underlying Java class object.

Sources/SwiftJava/Optional+JavaOptional.swift

@@ -79,3 +79,17 @@ public extension Optional where Wrapped == Int64 {
     }
   }
 }
+
+extension JavaOptional {
+  public func empty(environment: JNIEnvironment? = nil) -> JavaOptional<T>! {
+    guard let env = try? environment ?? JavaVirtualMachine.shared().environment() else {
+      return nil
+    }
+
+    guard let opt = try? JavaClass<JavaOptional<T>>(environment: env).empty() else {
+      return nil
+    }
+
+    return opt.as(JavaOptional<T>.self)
+  }
+}

Sources/SwiftJava/String+Extensions.swift

@@ -13,10 +13,6 @@
 //===----------------------------------------------------------------------===//
 
 import Foundation
-// import SwiftJavaToolLib
-// import SwiftJava
-// import JavaUtilJar
-// import SwiftJavaConfigurationShared
 
 extension String {
   /// For a String that's of the form java.util.Vector, return the "Vector"