From f9109549280c62472597ba952f10711b8768aa4b Mon Sep 17 00:00:00 2001
From: Petri Virkkunen <petri.virkkunen@qt.io>
Date: Wed, 8 Jan 2025 16:03:49 +0200
Subject: [PATCH] Android: JNI: Use void as default return value type on
 call[Static]Method

By using void as default template argument in callStaticMethod and
callMethod, we can avoid having to type <void> after every void method
call, while still allowing the caller to remain explicit about the type
if they want to.

Change-Id: Id7143d1116364be7699712d1fead257f26f20420
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
---
 src/corelib/kernel/qjniobject.h               | 20 +++++++-------
 .../kernel/qjniobject/tst_qjniobject.cpp      | 26 +++++++++++++++++++
 2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/src/corelib/kernel/qjniobject.h b/src/corelib/kernel/qjniobject.h
index 79178d6b0ca..7ff30fc1d99 100644
--- a/src/corelib/kernel/qjniobject.h
+++ b/src/corelib/kernel/qjniobject.h
@@ -132,7 +132,7 @@ public:
     jclass objectClass() const;
     QByteArray className() const;
 
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidFieldType<Ret> = true
 #endif
@@ -164,7 +164,7 @@ public:
         }
     }
 
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
@@ -191,7 +191,7 @@ public:
 
     QJniObject callObjectMethod(const char *methodName, const char *signature, ...) const;
 
-    template <typename Ret, typename ...Args>
+    template <typename Ret = void, typename ...Args>
     static auto callStaticMethod(const char *className, const char *methodName, const char *signature, Args &&...args)
     {
         JNIEnv *env = QJniEnvironment::getJniEnv();
@@ -199,7 +199,7 @@ public:
         return callStaticMethod<Ret>(clazz, methodName, signature, std::forward<Args>(args)...);
     }
 
-    template <typename Ret, typename ...Args>
+    template <typename Ret = void, typename ...Args>
     static auto callStaticMethod(jclass clazz, const char *methodName, const char *signature, Args &&...args)
     {
         JNIEnv *env = QJniEnvironment::getJniEnv();
@@ -208,7 +208,7 @@ public:
         return callStaticMethod<Ret>(clazz, id, std::forward<Args>(args)...);
     }
 
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidFieldType<Ret> = true
 #endif
@@ -239,7 +239,7 @@ public:
         }
     }
 
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
@@ -254,7 +254,7 @@ public:
         return callStaticMethod<Ret>(clazz, id, std::forward<Args>(args)...);
     }
 
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
@@ -264,7 +264,7 @@ public:
         constexpr auto signature = QtJniTypes::methodSignature<Ret, Args...>();
         return callStaticMethod<Ret>(clazz, methodName, signature.data(), std::forward<Args>(args)...);
     }
-    template <typename Klass, typename Ret, typename ...Args
+    template <typename Klass, typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
@@ -761,7 +761,7 @@ public:
     }
 
     // public API forwarding to QJniObject, with the implicit Class template parameter
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
@@ -791,7 +791,7 @@ public:
     }
 
     // keep only these overloads, the rest is made private
-    template <typename Ret, typename ...Args
+    template <typename Ret = void, typename ...Args
 #ifndef Q_QDOC
         , QtJniTypes::IfValidSignatureTypes<Ret, Args...> = true
 #endif
diff --git a/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp b/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
index 6291c70fdeb..399f1a74deb 100644
--- a/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
+++ b/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
@@ -113,6 +113,7 @@ private slots:
     void setStaticObjectField();
 
     void templateApiCheck();
+    void defaultTemplateApiCheck();
     void isClassAvailable();
     void fromLocalRef();
     void largeObjectArray();
@@ -1875,6 +1876,31 @@ void tst_QJniObject::templateApiCheck()
 
 }
 
+void tst_QJniObject::defaultTemplateApiCheck()
+{
+    // static QJniObject calls --------------------------------------------------------------------
+    QJniObject::callStaticMethod(testClassName, "staticVoidMethod");
+    QJniObject::callStaticMethod(testClassName, "staticVoidMethodWithArgs", "(IZC)V", 1, true, 'c');
+    QJniObject::callStaticMethod(testClassName, "staticVoidMethodWithArgs", 1, true, 'c');
+
+    // instance QJniObject calls ------------------------------------------------------------------
+    QJniObject testClass(testClassName);
+    QVERIFY(testClass.isValid());
+
+    testClass.callMethod("voidMethod");
+    testClass.callMethod("voidMethodWithArgs", "(IZC)V", 1, true, 'c');
+    testClass.callMethod("voidMethodWithArgs", 1, true, 'c');
+
+    // static QtJniType calls ---------------------------------------------------------------------
+    TestClass::callStaticMethod("staticVoidMethod");
+    TestClass::callStaticMethod("staticVoidMethodWithArgs", 1, true, 'c');
+
+    // instance QtJniType calls -------------------------------------------------------------------
+    TestClass instance;
+    instance.callMethod("voidMethod");
+    instance.callMethod("voidMethodWithArgs", 1, true, 'c');
+}
+
 void tst_QJniObject::isClassAvailable()
 {
     QVERIFY(QJniObject::isClassAvailable("java/lang/String"));