fix(cpp): check if JVM is initialized in KotlinLanguage::thread_enter and KotlinLanguage::thread_exit as a quick fix for project setup problems (#559)

Author: piiertho

src/jni/jvm.h

@@ -31,6 +31,8 @@ namespace jni {
 
         static Type get_type();
 
+        static bool is_initialized();
+
     private:
         Jvm() = default;
         static JavaVM* vm;

src/jni/platforms/jvm_android.cpp

@@ -45,6 +45,10 @@ namespace jni {
     Jvm::Type Jvm::get_type() {
         return vm_type;
     }
+
+    bool Jvm::is_initialized() {
+        return true;
+    }
 }// namespace jni
 
 #endif

src/jni/platforms/jvm_default.cpp

@@ -100,6 +100,10 @@ namespace jni {
     Jvm::Type Jvm::get_type() {
         return vm_type;
     }
+
+    bool Jvm::is_initialized() {
+        return vm;
+    }
 }// namespace jni
 
 #endif

src/kotlin_language.cpp

@@ -277,10 +277,26 @@ void KotlinLanguage::remove_named_global_constant(const StringName& p_name) {
 }
 
 void KotlinLanguage::thread_enter() {
+    //TODO: Remove this ifdef and its content while reworking GDKotlin and moving out logic of finding JVM.
+#ifdef DEBUG_ENABLED
+    if (!jni::Jvm::is_initialized()) {
+        LOG_ERROR("JavaVM is not initialized, please make sure your project contains an embedded JVM or JAVA_HOME environment variable is setup");
+        return;
+    }
+#endif
+
     jni::Jvm::attach();
 }
 
 void KotlinLanguage::thread_exit() {
+    //TODO: Remove this ifdef and its content while reworking GDKotlin and moving out logic of finding JVM.
+#ifdef DEBUG_ENABLED
+    if (!jni::Jvm::is_initialized()) {
+        LOG_ERROR("JavaVM is not initialized, please make sure your project contains an embedded JVM or JAVA_HOME environment variable is setup");
+        return;
+    }
+#endif
+
     jni::Jvm::detach();
 }