fix throwing functions

Author: madsodgaard

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/CallbackProtcol.swift

@@ -31,6 +31,8 @@ public protocol CallbackProtocol {
   func withInt64Array(_ input: [Int64]) -> [Int64]
   func withStringArray(_ input: [String]) -> [String]
   func withObjectArray(_ input: [MySwiftClass]) -> [MySwiftClass]
+  func successfulThrowingFunction() throws
+  func throwingFunction() throws
 }
 
 public struct CallbackOutput {
@@ -51,6 +53,18 @@ public struct CallbackOutput {
   public let objectArray: [MySwiftClass]
 }
 
+public func callProtocolVoid(_ callbacks: some CallbackProtocol) {
+  callbacks.withVoid();
+}
+
+public func callProtocolWithFailedThrowingFunction(_ callbacks: some CallbackProtocol) throws {
+  try callbacks.throwingFunction();
+}
+
+public func callProtocolWithSuccessfulThrowingFunction(_ callbacks: some CallbackProtocol) throws {
+  try callbacks.successfulThrowingFunction();
+}
+
 public func outputCallbacks(
   _ callbacks: some CallbackProtocol,
   bool: Bool,

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/ProtocolCallbacksTest.java

@@ -102,6 +102,35 @@ public String[] withStringArray(String[] input) {
         public MySwiftClass[] withObjectArray(MySwiftClass[] input, SwiftArena swiftArena$) {
             return input;
         }
+
+        @Override
+        public void throwingFunction() throws Exception {
+            throw new Exception("Failed in Java");
+        }
+
+        @Override
+        public void successfulThrowingFunction() throws Exception {
+
+        }
+    }
+
+    @Test
+    void voidTest() {
+        JavaCallbacks callbacks = new JavaCallbacks();
+        MySwiftLibrary.callProtocolVoid(callbacks);
+    }
+
+    @Test
+    void throwingFunction_thatDoesNotThrow() {
+        JavaCallbacks callbacks = new JavaCallbacks();
+        assertDoesNotThrow(() -> MySwiftLibrary.callProtocolWithSuccessfulThrowingFunction(callbacks));
+    }
+
+    @Test
+    void throwingFunction_thatThrows() {
+        JavaCallbacks callbacks = new JavaCallbacks();
+        Exception exception = assertThrows(Exception.class, () -> MySwiftLibrary.callProtocolWithFailedThrowingFunction(callbacks));
+        assertEquals("Failed in Java", exception.getMessage());
     }
 
     @Test

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -153,7 +153,8 @@ extension JNISwift2JavaGenerator {
         conversion.render(&printer, param.parameterName!)
       }
 
-      let javaUpcall = "\(wrapper.javaInterfaceVariableName).\(function.swiftFunctionName)(\(upcallArguments.joined(separator: ", ")))"
+      let tryClause = function.originalFunctionSignature.isThrowing ? "try " : ""
+      let javaUpcall = "\(tryClause)\(wrapper.javaInterfaceVariableName).\(function.swiftFunctionName)(\(upcallArguments.joined(separator: ", ")))"
 
       let resultType = function.originalFunctionSignature.result.type
       let result = function.resultConversion.render(&printer, javaUpcall)