JNI: Foundation values as standard Java types

Package.swift

@@ -481,6 +481,7 @@ let package = Package(
       name: "SwiftJavaTests",
       dependencies: [
         "SwiftJava",
+        "SwiftJavaRuntimeSupport",
         "JavaNet",
       ],
       swiftSettings: [

Samples/SwiftJavaExtractJNIKotlinSampleApp/Sources/KotlinSampleLibrary/Bookmarks.swift

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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 Foundation
+
+/// Foundation values cross as standard Java types (`foundationTypesAsJavaTypes`).
+public final class Bookmark {
+  public var url: URL
+  public var icon: URL?
+  public var created: Date
+  public var thumbnail: Data
+  public var locale: Locale
+  public var timeZone: TimeZone
+  public var zoom: CGFloat
+  public var onOpen: ((URL) -> Void)?
+
+  public init(url: URL, icon: URL?, created: Date, thumbnail: Data, locale: Locale, timeZone: TimeZone, zoom: CGFloat) {
+    self.url = url
+    self.icon = icon
+    self.created = created
+    self.thumbnail = thumbnail
+    self.locale = locale
+    self.timeZone = timeZone
+    self.zoom = zoom
+  }
+
+  public func open() {
+    onOpen?(url)
+  }
+
+  public func observeVisits(_ onVisit: @escaping (URL, Date) -> Void) {
+    onVisit(url, created)
+  }
+
+  public func related() -> [URL] {
+    [url, url.appendingPathComponent("more")]
+  }
+
+  public func refreshed() async -> Date {
+    created.addingTimeInterval(60)
+  }
+}

Samples/SwiftJavaExtractJNIKotlinSampleApp/Sources/KotlinSampleLibrary/swift-java.config

@@ -6,5 +6,6 @@
   "payloadlessEnumsAsJavaEnums": true,
   "optionalsAsNullable": true,
   "nullableAnnotation": "org.jetbrains.annotations.Nullable",
-  "nonNullAnnotation": "org.jetbrains.annotations.NotNull"
+  "nonNullAnnotation": "org.jetbrains.annotations.NotNull",
+  "foundationTypesAsJavaTypes": true
 }

Samples/SwiftJavaExtractJNIKotlinSampleApp/src/test/kotlin/com/example/kotlin/FoundationValuesTest.kt

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+package com.example.kotlin
+
+import java.net.URI
+import java.util.Date
+import java.util.Locale
+import java.util.TimeZone
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+// URL, Date, Data, Locale and TimeZone are java.net.URI, java.util.Date, ByteArray, java.util.Locale and
+// java.util.TimeZone in Kotlin, and CGFloat is a Double.
+class FoundationValuesTest {
+    private fun bookmark() = Bookmark.init(
+        URI.create("https://swift.org/docs"),
+        null,
+        Date(1_700_000_000_123),
+        byteArrayOf(1, 2, -1),
+        Locale.forLanguageTag("pt-BR"),
+        TimeZone.getTimeZone("Europe/Rome"),
+        1.5,
+    )
+
+    @Test
+    fun valuesRoundTrip() {
+        val bookmark = bookmark()
+        assertEquals(URI.create("https://swift.org/docs"), bookmark.url)
+        assertNull(bookmark.icon)
+        bookmark.icon = URI.create("https://swift.org/favicon.ico")
+        assertEquals("https://swift.org/favicon.ico", bookmark.icon.toString())
+        assertEquals(1_700_000_000_123, bookmark.created.time)
+        assertContentEquals(byteArrayOf(1, 2, -1), bookmark.thumbnail)
+        assertEquals("pt-BR", bookmark.locale.toLanguageTag())
+        assertEquals("Europe/Rome", bookmark.timeZone.id)
+        assertEquals(1.5, bookmark.zoom)
+        assertEquals(listOf("https://swift.org/docs", "https://swift.org/docs/more"), bookmark.related().map { it.toString() })
+    }
+
+    @Test
+    fun closures() {
+        val bookmark = bookmark()
+        val opened = mutableListOf<URI>()
+        bookmark.onOpen = { opened += it }
+        bookmark.open()
+        assertEquals(listOf(URI.create("https://swift.org/docs")), opened)
+
+        var visit: Pair<URI, Date>? = null
+        bookmark.observeVisits { url, date -> visit = url to date }
+        assertEquals(URI.create("https://swift.org/docs") to Date(1_700_000_000_123), visit)
+    }
+
+    @Test
+    fun asyncResult() {
+        assertEquals(1_700_000_060_123, bookmark().refreshed().get().time)
+    }
+}

Sources/JExtractSwiftLib/Convenience/JavaType+Extensions.swift

@@ -60,13 +60,16 @@ extension JavaType {
     case .float: "Optional<Float>"
     case .double: "OptionalDouble"
     case .javaLangString: "Optional<String>"
+    case .javaNetURI, .javaUtilDate, .javaUtilLocale, .javaUtilTimeZone, .array(.byte): "Optional<\(self)>"
     default: nil
     }
   }
 
   var optionalWrapperType: String? {
     switch self {
-    case .boolean, .byte, .char, .short, .float, .javaLangString: "Optional"
+    case .boolean, .byte, .char, .short, .float, .javaLangString,
+      .javaNetURI, .javaUtilDate, .javaUtilLocale, .javaUtilTimeZone, .array(.byte):
+      "Optional"
     case .int: "OptionalInt"
     case .long: "OptionalLong"
     case .double: "OptionalDouble"
@@ -130,7 +133,8 @@ extension JavaType {
   /// Returns whether this type returns `JavaValue` from SwiftJava
   var implementsJavaValue: Bool {
     switch self {
-    case .boolean, .byte, .char, .short, .int, .long, .float, .double, .void, .javaLangString:
+    case .boolean, .byte, .char, .short, .int, .long, .float, .double, .void, .javaLangString,
+      .javaNetURI, .javaUtilDate, .javaUtilLocale, .javaUtilTimeZone:
       true
     case .array(let element):
       element.implementsJavaValue

Sources/JExtractSwiftLib/JNI/JNIJavaTypeTranslator.swift

@@ -42,21 +42,31 @@ enum JNIJavaTypeTranslator {
 
     case .string: return .javaLangString
 
+    case .foundationCGFloat: return .double
+
+    case .foundationURL, .essentialsURL:
+      return config.effectiveFoundationTypesAsJavaTypes ? .javaNetURI : nil
+    case .foundationDate, .essentialsDate:
+      return config.effectiveFoundationTypesAsJavaTypes ? .javaUtilDate : nil
+    case .foundationData, .essentialsData:
+      return config.effectiveFoundationTypesAsJavaTypes ? .array(.byte) : nil
+    case .foundationLocale, .essentialsLocale:
+      return config.effectiveFoundationTypesAsJavaTypes ? .javaUtilLocale : nil
+    case .foundationTimeZone, .essentialsTimeZone:
+      return config.effectiveFoundationTypesAsJavaTypes ? .javaUtilTimeZone : nil
+
     case .unsafeRawPointer, .unsafeMutableRawPointer,
       .unsafePointer, .unsafeMutablePointer,
       .unsafeRawBufferPointer, .unsafeMutableRawBufferPointer,
       .unsafeBufferPointer, .unsafeMutableBufferPointer,
       .opaquePointer,
       .optional,
-      .foundationData, .foundationDataProtocol,
-      .essentialsData, .essentialsDataProtocol,
+      .foundationDataProtocol, .essentialsDataProtocol,
       .array,
       .dictionary,
       .set,
       .asyncStream, .asyncThrowingStream, .error,
-      .foundationDate, .essentialsDate,
-      .foundationUUID, .essentialsUUID,
-      .foundationURL, .essentialsURL:
+      .foundationUUID, .essentialsUUID:
       return nil
     }
   }
@@ -68,6 +78,7 @@ enum JNIJavaTypeTranslator {
     switch knownKind {
     case .int: knownTypes.int64
     case .uint: knownTypes.uint64
+    case .foundationCGFloat: knownTypes.double
 
     case .bool, .int8, .uint8, .int16, .uint16, .int32, .uint32, .int64, .uint64,
       .float, .double, .void, .string,
@@ -85,7 +96,9 @@ enum JNIJavaTypeTranslator {
       .asyncStream, .asyncThrowingStream, .error,
       .foundationDate, .essentialsDate,
       .foundationUUID, .essentialsUUID,
-      .foundationURL, .essentialsURL:
+      .foundationURL, .essentialsURL,
+      .foundationLocale, .essentialsLocale,
+      .foundationTimeZone, .essentialsTimeZone:
       nil
     }
   }
@@ -114,7 +127,10 @@ enum JNIJavaTypeTranslator {
       .asyncStream, .asyncThrowingStream, .error,
       .foundationDate, .essentialsDate,
       .foundationUUID, .essentialsUUID,
-      .foundationURL, .essentialsURL:
+      .foundationURL, .essentialsURL,
+      .foundationLocale, .essentialsLocale,
+      .foundationTimeZone, .essentialsTimeZone,
+      .foundationCGFloat:
       nil
     }
   }

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+InterfaceWrapperGeneration.swift

@@ -34,6 +34,8 @@ extension JNISwift2JavaGenerator {
       }
 
       do {
+        // wrap-java maps `java.net.URI` and the other Foundation Java types on its own terms, so
+        // protocols implemented in Java don't pass Foundation values as they are; closures do.
         let translator = JavaInterfaceProtocolWrapperGenerator(asyncFuncMode: config.effectiveAsyncFuncMode)
         wrappers[type] = try translator.generate(for: type)
       } catch {
@@ -105,6 +107,13 @@ extension JNISwift2JavaGenerator {
 
   struct JavaInterfaceProtocolWrapperGenerator {
     var asyncFuncMode: JExtractAsyncFuncMode = .default
+    /// Foundation values are `JavaValue`s that cross as Java types, as `String` does. Only for closures, whose
+    /// `@JavaInterface` jextract prints itself.
+    var foundationTypesAsJavaTypes: Bool = false
+
+    private func crossesAsIs(_ type: SwiftType) -> Bool {
+      type.isDirectlyTranslatedToWrapJava || (foundationTypesAsJavaTypes && type.isFoundationJavaValue)
+    }
 
     func generate(for type: ExtractedNominalType) throws -> JavaInterfaceSwiftWrapper {
       if !type.initializers.isEmpty
@@ -238,7 +247,7 @@ extension JNISwift2JavaGenerator {
 
     private func translateParameter(parameterName: String, type: SwiftType) throws -> UpcallConversionStep {
 
-      if type.isDirectlyTranslatedToWrapJava {
+      if crossesAsIs(type) {
         return .placeholder
       }
       if type.isSwiftError {
@@ -322,7 +331,7 @@ extension JNISwift2JavaGenerator {
       methodName: String,
       allowNilForObjects: Bool = false
     ) throws -> UpcallConversionStep {
-      if type.isDirectlyTranslatedToWrapJava {
+      if crossesAsIs(type) {
         return .placeholder
       }
 
@@ -507,6 +516,20 @@ enum UpcallConversionStep {
 }
 
 extension SwiftType {
+  /// A Foundation value that conforms to `JavaValue` in SwiftJavaRuntimeSupport, used with `foundationTypesAsJavaTypes`
+  var isFoundationJavaValue: Bool {
+    guard case .nominal(let nominal) = self, let kind = nominal.nominalTypeDecl.knownTypeKind else {
+      return false
+    }
+    switch kind {
+    case .foundationURL, .essentialsURL, .foundationDate, .essentialsDate, .foundationData, .essentialsData,
+      .foundationLocale, .essentialsLocale, .foundationTimeZone, .essentialsTimeZone:
+      return true
+    default:
+      return false
+    }
+  }
+
   /// Indicates whether this type is translated by `wrap-java`
   /// into the same type as `jextract`.
   ///

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift

@@ -664,7 +664,12 @@ extension JNISwift2JavaGenerator {
               genericRequirements: genericRequirements,
             )
 
-          case .foundationDate, .essentialsDate, .foundationData, .essentialsData, .foundationURL, .essentialsURL:
+          case .foundationDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .foundationData where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsData where !config.effectiveFoundationTypesAsJavaTypes,
+            .foundationURL where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsURL where !config.effectiveFoundationTypesAsJavaTypes:
             break // Handled as wrapped struct
 
           case .unsafeRawBufferPointer, .unsafeMutableRawBufferPointer:
@@ -1105,14 +1110,17 @@ extension JNISwift2JavaGenerator {
       guard case .class(_, let name, let typeParameters) = type else {
         return nil
       }
+      // Spelled as one class name, such as `Optional<Boolean>` or `Optional<java.net.URI>`. The dots in
+      // the latter split it into a package and a name, so match the whole spelling.
+      let spelling = type.description
+      if typeParameters.isEmpty, spelling.hasPrefix("Optional<"), spelling.hasSuffix(">") {
+        return (JavaType(className: String(spelling.dropFirst("Optional<".count).dropLast())), "get")
+      }
       switch name {
       case "OptionalLong": return (.class(package: "java.lang", name: "Long"), "getAsLong")
       case "OptionalInt": return (.class(package: "java.lang", name: "Integer"), "getAsInt")
       case "OptionalDouble": return (.class(package: "java.lang", name: "Double"), "getAsDouble")
       case "Optional" where typeParameters.count == 1: return (typeParameters[0], "get")
-      // Primitive optionals spelled as one class name, such as `Optional<Boolean>`
-      case _ where name.hasPrefix("Optional<") && name.hasSuffix(">"):
-        return (JavaType(className: name.dropFirst("Optional<".count).dropLast()), "get")
       default: return nil
       }
     }
@@ -1169,11 +1177,13 @@ extension JNISwift2JavaGenerator {
 
         if let knownType = nominalType.nominalTypeDecl.knownTypeKind {
           switch knownType {
-          case .foundationDate, .essentialsDate:
+          case .foundationDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsDate where !config.effectiveFoundationTypesAsJavaTypes:
             // Handled as wrapped struct
             break
 
-          case .foundationData, .essentialsData:
+          case .foundationData where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsData where !config.effectiveFoundationTypesAsJavaTypes:
             // Handled as wrapped struct
             break
 
@@ -1309,7 +1319,12 @@ extension JNISwift2JavaGenerator {
               genericRequirements: genericRequirements,
             )
 
-          case .foundationDate, .essentialsDate, .foundationData, .essentialsData, .foundationURL, .essentialsURL:
+          case .foundationDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .foundationData where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsData where !config.effectiveFoundationTypesAsJavaTypes,
+            .foundationURL where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsURL where !config.effectiveFoundationTypesAsJavaTypes:
             // Handled as wrapped struct
             break
 
@@ -1499,16 +1514,19 @@ extension JNISwift2JavaGenerator {
             )
             return .swiftSet(elementJavaType)
 
-          case .foundationDate, .essentialsDate:
+          case .foundationDate where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsDate where !config.effectiveFoundationTypesAsJavaTypes:
             return .class(package: nil, name: "Date")
 
-          case .foundationData, .essentialsData:
+          case .foundationData where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsData where !config.effectiveFoundationTypesAsJavaTypes:
             return .class(package: nil, name: "Data")
 
           case .foundationDataProtocol, .essentialsDataProtocol:
             return .class(package: nil, name: "DataProtocol")
 
-          case .foundationURL, .essentialsURL:
+          case .foundationURL where !config.effectiveFoundationTypesAsJavaTypes,
+            .essentialsURL where !config.effectiveFoundationTypesAsJavaTypes:
             return .class(package: nil, name: "URL")
 
           case .foundationUUID, .essentialsUUID: