Partial 7.0 merge - API preview

core/src/mindustry/mod/ModClassLoader.java

@@ -0,0 +1,35 @@
+package mindustry.mod;
+
+import arc.struct.*;
+
+public class ModClassLoader extends ClassLoader{
+    private Seq<ClassLoader> children = new Seq<>();
+    private volatile boolean inChild = false;
+
+    public void addChild(ClassLoader child){
+        children.add(child);
+    }
+
+    @Override
+    protected synchronized Class<?> loadClass(String name, boolean resolve) 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;
+            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++){
+                try{
+                    inChild = true;
+                    var out = children.get(i).loadClass(name);
+                    inChild = false;
+                    return out;
+                }catch(ClassNotFoundException ignored){
+                }
+            }
+            throw error;
+        }
+    }
+}