Fix JDWP method invocation and add tests

- Fix null ClassLoader NPE in ReferenceTypeCommandSet (Error 113)
- Fix getNoDeclaredInterfaces() -> getNoInterfaces() for interface resolution
- Extract MethodResolver utility class for shared method resolution logic
- Implement InterfaceType methods/methodsWithGeneric commands
- Add .gitignore for __pycache__/
- Add test_method_invocation.py with 23 integration tests

Author: LSantha

.gitignore

@@ -16,3 +16,4 @@ classlib.pack.gz
 /.metadata
 /.idea/
 /.wiki/
+__pycache__/

core/src/classpath/ext/gnu/classpath/jdwp/JdwpConstants.java

@@ -131,6 +131,8 @@ public static final class InterfaceType
       public static final byte CS_VALUE = 5;
 
       // commands
+      public static final byte METHODS = 1;
+      public static final byte METHOD_WITH_GENERIC = 2;
     }
 
     public static final class Method

core/src/classpath/ext/gnu/classpath/jdwp/processor/ClassTypeCommandSet.java

@@ -59,7 +59,6 @@
 import java.lang.reflect.Member;
 import java.nio.ByteBuffer;
 import org.jnode.vm.classmgr.VmType;
-import org.jnode.vm.classmgr.VmNormalClass;
 import org.jnode.vm.classmgr.VmMethod;
 
 /**
@@ -111,12 +110,15 @@ private void executeSuperclass(ByteBuffer bb, DataOutputStream os)
     Class clazz = refId.getType();
     Class superClazz = clazz.getSuperclass();
 
-    if (superClazz == null) {
-    	os.writeLong(0L);
-    } else {
-    ReferenceTypeId clazzId = idMan.getReferenceTypeId(superClazz);
-    clazzId.write(os);
-  }
+    if (superClazz == null)
+      {
+        os.writeLong(0L);
+      }
+    else
+      {
+        ReferenceTypeId clazzId = idMan.getReferenceTypeId(superClazz);
+        clazzId.write(os);
+      }
   }
 
   private void executeSetValues(ByteBuffer bb, DataOutputStream os)
@@ -225,58 +227,10 @@ private MethodResult invokeMethod(ByteBuffer bb) throws JdwpException,
         values[i] = Value.getObj(bb);
       }
 
-    // Resolve member (method/constructor) from class or superclass using index and parameter count matching
-    Member member = null;
+    // Resolve member (method/constructor) from class or superclass using index and parameter count matching.
+    // Walk the full hierarchy: superclass chain + all implemented interfaces.
     VmType vmType = VmType.fromClass(clazz);
-    VmType searchType = vmType;
-    while (searchType != null && member == null)
-      {
-        int nMethods = searchType.getNoDeclaredMethods();
-        if (methodIdx >= 0 && methodIdx < nMethods)
-          {
-            VmMethod vmMethod = searchType.getDeclaredMethod((int) methodIdx);
-            if (vmMethod != null)
-              {
-                Member candidate = vmMethod.asMember();
-                int paramCount = (candidate instanceof Method)
-                    ? ((Method) candidate).getParameterTypes().length
-                    : ((Constructor) candidate).getParameterTypes().length;
-                if (paramCount == values.length)
-                  {
-                    member = candidate;
-                    break;
-                  }
-              }
-          }
-        if (searchType instanceof VmNormalClass)
-          {
-            searchType = ((VmNormalClass) searchType).getSuperClass();
-          }
-        else
-          {
-            break;
-          }
-      }
-
-    // Fallback: search Java reflection declared methods across class hierarchy
-    if (member == null)
-      {
-        Class curClass = clazz;
-        while (curClass != null && member == null)
-          {
-            Method[] declared = curClass.getDeclaredMethods();
-            if (methodIdx >= 0 && methodIdx < declared.length)
-              {
-                Method candidate = declared[(int) methodIdx];
-                if (candidate.getParameterTypes().length == values.length)
-                  {
-                    member = candidate;
-                    break;
-                  }
-              }
-            curClass = curClass.getSuperclass();
-          }
-      }
+    Member member = MethodResolver.resolveForClassType(vmType, clazz, methodIdx, values.length);
 
     if (member == null)
       {

core/src/classpath/ext/gnu/classpath/jdwp/processor/InterfaceTypeCommandSet.java

@@ -39,11 +39,18 @@
 
 package gnu.classpath.jdwp.processor;
 
+import gnu.classpath.jdwp.JdwpConstants;
 import gnu.classpath.jdwp.exception.JdwpException;
+import gnu.classpath.jdwp.exception.JdwpInternalErrorException;
 import gnu.classpath.jdwp.exception.NotImplementedException;
+import gnu.classpath.jdwp.id.ReferenceTypeId;
+import gnu.classpath.jdwp.util.JdwpString;
 
 import java.io.DataOutputStream;
+import java.io.IOException;
 import java.nio.ByteBuffer;
+import org.jnode.vm.classmgr.VmType;
+import org.jnode.vm.classmgr.VmMethod;
 
 /**
  * A class representing the InterfaceType Command Set.
@@ -53,16 +60,58 @@
 public class InterfaceTypeCommandSet
   extends CommandSet
 {
-  /**
-   * There are no commands for this CommandSet at this time so we just throw a
-   * NotImplementedException whenever it's called.
-   * 
-   * @throws JdwpException An exception will always be thrown
-   */
   public boolean runCommand(ByteBuffer bb, DataOutputStream os, byte command)
     throws JdwpException
   {
-    throw new NotImplementedException(
-      "No commands for command set InterfaceType implemented.");
+    try
+      {
+        switch (command)
+          {
+          case JdwpConstants.CommandSet.InterfaceType.METHODS:
+            executeMethods(bb, os);
+            break;
+          case JdwpConstants.CommandSet.InterfaceType.METHOD_WITH_GENERIC:
+            executeMethodWithGeneric(bb, os);
+            break;
+          default:
+            throw new NotImplementedException(
+              "Command " + command + " not found in InterfaceType Command Set.");
+          }
+      }
+    catch (IOException ex)
+      {
+        throw new JdwpInternalErrorException(ex);
+      }
+
+    return false;
+  }
+
+  /**
+   * List methods declared in this interface.
+   */
+  private void executeMethods(ByteBuffer bb, DataOutputStream os)
+    throws JdwpException, IOException
+  {
+    ReferenceTypeId refId = idMan.readReferenceTypeId(bb);
+    Class clazz = refId.getType();
+    VmType vmType = VmType.fromClass(clazz);
+
+    int count = (vmType == null) ? 0 : vmType.getNoDeclaredMethods();
+    os.writeInt(count);
+    for (int i = 0; i < count; i++)
+      {
+        VmMethod vmMethod = vmType.getDeclaredMethod(i);
+        os.writeLong(i);
+        JdwpString.writeString(os, vmMethod.getName());
+        JdwpString.writeString(os, vmMethod.getSignature());
+        os.writeInt(vmMethod.getModifiers());
+      }
+  }
+
+  private void executeMethodWithGeneric(ByteBuffer bb, DataOutputStream os)
+    throws JdwpException, IOException
+  {
+    // Reuse executeMethods - generic signatures are not tracked separately
+    executeMethods(bb, os);
   }
 }