Skip to content

jextract: support returning JavaKit wrapped Java objects (Resolves #841) #851

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
amanmaurya92 wants to merge 3 commits into
base: main
Choose a base branch
from
Open

jextract: support returning JavaKit wrapped Java objects (Resolves #841) #851

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
3ed5aa3
jextract: support returning JavaKit wrapped Java objects (Resolves #841)
amanmaurya92 Jul 27, 2026
97de0a5
Fix JNI thunk generation for JavaKit wrapped return types
amanmaurya92 Aug 1, 2026
859f5bb
Add runtime test for returning JavaKit objects
amanmaurya92 Aug 1, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 4 additions & 0 deletions Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/MySwiftClass.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,10 @@ public class MySwiftClass {
public func addXWithJavaLong(_ other: JavaLong) -> Int64 {
self.x + other.longValue()
}

public func returnXAsJavaLong() -> JavaLong {
JavaLong(self.x)
}
}

extension MySwiftClass: CustomStringConvertible {
Expand Down
9 changes: 9 additions & 0 deletions Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/MySwiftClassTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,15 @@ void addXWithJavaLong() {
}
}

@Test
void returnXAsJavaLong() {
try (var arena = SwiftArena.ofConfined()) {
MySwiftClass c1 = MySwiftClass.init(20, 10, arena);
Long javaLong = c1.returnXAsJavaLong();
assertEquals(20L, javaLong);
}
}

@Test
void getAsyncVariable() throws Exception {
try (var arena = SwiftArena.ofConfined()) {
Expand Down
41 changes: 36 additions & 5 deletions Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -899,6 +899,7 @@ extension JNISwift2JavaGenerator {

switch swiftType {
case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.asKnownType {
switch knownType {
case .optional(let wrapped):
Expand Down Expand Up @@ -964,7 +965,16 @@ extension JNISwift2JavaGenerator {
}

if nominalType.isSwiftJavaWrapper {
throw JavaTranslationError.unsupportedSwiftType(swiftType)
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(swiftType)
}
return TranslatedResult(
javaType: javaType,
nativeJavaType: javaType,
annotations: resultAnnotations,
outParameters: [],
conversion: .placeholder
)
}

let javaType = JavaType.class(
Expand Down Expand Up @@ -1292,6 +1302,7 @@ extension JNISwift2JavaGenerator {

switch swiftType {
case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.nominalTypeDecl.knownTypeKind {
if let javaType = JNIJavaTypeTranslator.translate(knownType: knownType, config: self.config),
javaType.implementsJavaValue
Expand Down Expand Up @@ -1339,8 +1350,17 @@ extension JNISwift2JavaGenerator {
}
}

guard !nominalType.isSwiftJavaWrapper else {
throw JavaTranslationError.unsupportedSwiftType(swiftType)
if nominalType.isSwiftJavaWrapper {
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(swiftType)
}
return TranslatedResult(
javaType: javaType,
nativeJavaType: javaType,
annotations: parameterAnnotations,
outParameters: [],
conversion: .placeholder
)
}

case .tuple:
Expand Down Expand Up @@ -1488,6 +1508,7 @@ extension JNISwift2JavaGenerator {
)

case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.nominalTypeDecl.knownTypeKind {
guard let javaType = JNIJavaTypeTranslator.translate(knownType: knownType, config: self.config) else {
throw JavaTranslationError.unsupportedSwiftType(elementType)
Expand All @@ -1502,8 +1523,18 @@ extension JNISwift2JavaGenerator {
)
}

guard !nominalType.isSwiftJavaWrapper else {
throw JavaTranslationError.unsupportedSwiftType(elementType)
if nominalType.isSwiftJavaWrapper {
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(elementType)
}

return TranslatedResult(
javaType: .array(javaType),
nativeJavaType: .array(javaType),
annotations: annotations,
outParameters: [],
conversion: .placeholder
)
}

let javaType = try translateGenericTypeParameter(
Expand Down
37 changes: 31 additions & 6 deletions Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+NativeTranslation.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -649,6 +649,7 @@ extension JNISwift2JavaGenerator {

switch swiftType {
case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.nominalTypeDecl.knownTypeKind {
if let javaType = JNIJavaTypeTranslator.translate(knownType: knownType, config: self.config),
javaType.implementsJavaValue
Expand Down Expand Up @@ -697,9 +698,16 @@ extension JNISwift2JavaGenerator {
}
}

guard !nominalType.isSwiftJavaWrapper else {
// TODO: Should be the same as above
throw JavaTranslationError.unsupportedSwiftType(swiftType)
if nominalType.isSwiftJavaWrapper {
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(swiftType)
}

return NativeResult(
javaType: javaType,
conversion: .getJNIValue(.placeholder),
outParameters: []
)
}

case .tuple:
Expand Down Expand Up @@ -812,6 +820,7 @@ extension JNISwift2JavaGenerator {
) throws -> NativeResult {
switch swiftType {
case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.asKnownType {
switch knownType {
case .optional(let wrapped):
Expand Down Expand Up @@ -871,7 +880,14 @@ extension JNISwift2JavaGenerator {
}

if nominalType.isSwiftJavaWrapper {
throw JavaTranslationError.unsupportedSwiftType(swiftType)
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(swiftType)
}
return NativeResult(
javaType: javaType,
conversion: .getJNIValue(.placeholder),
outParameters: []
)
}

if nominalType.nominalTypeDecl.isGeneric {
Expand Down Expand Up @@ -1001,6 +1017,7 @@ extension JNISwift2JavaGenerator {
)

case .nominal(let nominalType):
let nominalTypeName = nominalType.nominalTypeDecl.qualifiedName
if let knownType = nominalType.nominalTypeDecl.knownTypeKind {
guard let javaType = JNIJavaTypeTranslator.translate(knownType: knownType, config: self.config),
javaType.implementsJavaValue
Expand All @@ -1015,8 +1032,16 @@ extension JNISwift2JavaGenerator {
)
}

guard !nominalType.isSwiftJavaWrapper else {
throw JavaTranslationError.unsupportedSwiftType(known: .array(elementType))
if nominalType.isSwiftJavaWrapper {
guard let javaType = nominalTypeName.parseJavaClassFromSwiftJavaName(in: self.javaClassLookupTable) else {
throw JavaTranslationError.wrappedJavaClassTranslationNotProvided(elementType)
}

return NativeResult(
javaType: .array(javaType),
conversion: .getJNIValue(.placeholder),
outParameters: []
)
}

// Assume JExtract imported class
Expand Down
138 changes: 136 additions & 2 deletions Tests/JExtractSwiftTests/JNI/JNIJavaKitTests.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,7 @@ import Testing

@Suite
struct JNIJavaKitTests {
let source =
"""
let source = """
public func function(javaLong: JavaLong, javaInteger: JavaInteger, int: Int64) {}
"""

Expand Down Expand Up @@ -77,4 +76,139 @@ struct JNIJavaKitTests {
]
)
}

@Test
func functionReturn_javaBindings() throws {
try assertOutput(
input: "public func function() -> JavaLong",
.jni,
.java,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
/**
* Downcall to Swift:
* {@snippet lang=swift :
* public func function() -> JavaLong
* }
*/
public static java.lang.Long function() {
return SwiftModule.$function();
}
""",
"""
private static native java.lang.Long $function();
""",
]
)
}

@Test
func functionReturn_swiftThunks() throws {
try assertOutput(
input: "public func function() -> JavaLong",
.jni,
.swift,
detectChunkByInitialLines: 1,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
@_cdecl("Java_com_example_swift_SwiftModule__00024function__")
public func Java_com_example_swift_SwiftModule__00024function__(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass) -> jobject? {
return SwiftModule.function().getJNILocalRefValue(in: environment)
}
"""
]
)
}

@Test
func functionReturnOptional_javaBindings() throws {
try assertOutput(
input: "public func function() -> JavaLong?",
.jni,
.java,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
/**
* Downcall to Swift:
* {@snippet lang=swift :
* public func function() -> JavaLong?
* }
*/
public static java.lang.Long function() {
return SwiftModule.$function();
}
""",
"""
private static native java.lang.Long $function();
""",
]
)
}

@Test
func functionReturnOptional_swiftThunks() throws {
try assertOutput(
input: "public func function() -> JavaLong?",
.jni,
.swift,
detectChunkByInitialLines: 1,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
@_cdecl("Java_com_example_swift_SwiftModule__00024function__")
public func Java_com_example_swift_SwiftModule__00024function__(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass) -> jobject? {
return SwiftModule.function().getJNILocalRefValue(in: environment)
}
"""
]
)
}

@Test
func functionReturnArray_javaBindings() throws {
try assertOutput(
input: "public func function() -> [JavaLong]",
.jni,
.java,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
/**
* Downcall to Swift:
* {@snippet lang=swift :
* public func function() -> [JavaLong]
* }
*/
public static java.lang.Long[] function() {
return SwiftModule.$function();
}
""",
"""
private static native java.lang.Long[] $function();
""",
]
)
}

@Test
func functionReturnArray_swiftThunks() throws {
try assertOutput(
input: "public func function() -> [JavaLong]",
.jni,
.swift,
detectChunkByInitialLines: 1,
javaClassLookupTable: classLookupTable,
expectedChunks: [
"""
@_cdecl("Java_com_example_swift_SwiftModule__00024function__")
public func Java_com_example_swift_SwiftModule__00024function__(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass) -> jobjectArray? {
return SwiftModule.function().getJNILocalRefValue(in: environment)
}
"""
]
)
}
}