Child-first mod class loading

android/src/mindustry/android/AndroidLauncher.java

@@ -75,7 +75,27 @@ public class AndroidLauncher extends AndroidApplication{
 
             @Override
             public ClassLoader loadJar(Fi jar, ClassLoader parent) throws Exception{
-                return new DexClassLoader(jar.file().getPath(), getFilesDir().getPath(), null, parent);
+                return new DexClassLoader(jar.file().getPath(), getFilesDir().getPath(), null, parent){
+                    @Override
+                    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException{
+                        //check for loaded state
+                        Class<?> loadedClass = findLoadedClass(name);
+                        if(loadedClass == null){
+                            try{
+                                //try to load own class first
+                                loadedClass = findClass(name);
+                            }catch(ClassNotFoundException e){
+                                //use parent if not found
+                                loadedClass = super.loadClass(name, resolve);
+                            }
+                        }
+
+                        if(resolve){
+                            resolveClass(loadedClass);
+                        }
+                        return loadedClass;
+                    }
+                };
             }
 
             @Override

core/src/mindustry/core/Platform.java

@@ -21,9 +21,29 @@ import static mindustry.Vars.*;
 
 public interface Platform{
 
-    /** Dynamically creates a class loader for a jar file. */
+    /** Dynamically creates a class loader for a jar file. This loader must be child-first. */
     default ClassLoader loadJar(Fi jar, ClassLoader parent) throws Exception{
-        return new URLClassLoader(new URL[]{jar.file().toURI().toURL()}, parent);
+        return new URLClassLoader(new URL[]{jar.file().toURI().toURL()}, parent){
+            @Override
+            protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException{
+                //check for loaded state
+                Class<?> loadedClass = findLoadedClass(name);
+                if(loadedClass == null){
+                    try{
+                        //try to load own class first
+                        loadedClass = findClass(name);
+                    }catch(ClassNotFoundException e){
+                        //use parent if not found
+                        loadedClass = super.loadClass(name, resolve);
+                    }
+                }
+
+                if(resolve){
+                    resolveClass(loadedClass);
+                }
+                return loadedClass;
+            }
+        };
     }
 
     /** Steam: Update lobby visibility.*/

core/src/mindustry/mod/ModClassLoader.java

@@ -11,13 +11,11 @@ public class ModClassLoader extends ClassLoader{
     }
 
     @Override
-    protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException{
+    protected Class<?> findClass(String name) throws ClassNotFoundException{
-        //always try the superclass first
-        try{
-            return super.loadClass(name, resolve);
-        }catch(ClassNotFoundException error){
         //a child may try to delegate class loading to its parent, which is *this class loader* - do not let that happen
-            if(inChild) throw error;
+        if(inChild) throw new ClassNotFoundException(name);
+
+        ClassNotFoundException last = null;
         int size = children.size;
         //if it doesn't exist in the main class loader, try all the children
         for(int i = 0; i < size; i++){
@@ -26,10 +24,10 @@ public class ModClassLoader extends ClassLoader{
                 var out = children.get(i).loadClass(name);
                 inChild = false;
                 return out;
-                }catch(ClassNotFoundException ignored){
+            }catch(ClassNotFoundException e){
+                last = e;
             }
         }
-            throw error;
+        throw (last == null ? new ClassNotFoundException(name) : last);
-        }
     }
 }