Add missing plugin functionality back, fixes #6944

core/src/main/java/org/apache/hop/metadata/serializer/xml/XmlMetadataUtil.java

@@ -27,6 +27,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.MissingResourceException;
 import java.util.Set;
 import org.apache.commons.lang3.StringUtils;
 import org.apache.hop.core.Const;
@@ -51,10 +52,42 @@
 import org.w3c.dom.Node;
 
 public class XmlMetadataUtil {
+
+  private static final String FQN_TRANSFORM_FACTORY =
+      "org.apache.hop.pipeline.transform.ITransformMeta$TransformFactory";
+  private static final String FQN_ACTION_FACTORY =
+      "org.apache.hop.workflow.action.IAction$ActionFactory";
+
   private XmlMetadataUtil() {
     // Hides the public constructor
   }
 
+  /**
+   * {@link MissingResourceException} from transform/action factories: substitute {@code Missing} /
+   * {@code MissingAction} via reflection (no core → engine compile dependency).
+   */
+  private static Object newMissingPluginPlaceholder(
+      HopMetadataObject metadataObject, Node node, String pluginId) {
+    String factoryName = metadataObject.objectFactory().getName();
+    String name = node != null ? XmlHandler.getTagValue(node, "name") : null;
+    try {
+      if (FQN_TRANSFORM_FACTORY.equals(factoryName)) {
+        Class<?> c = Class.forName("org.apache.hop.pipeline.transforms.missing.Missing");
+        return c.getDeclaredConstructor(String.class, String.class)
+            .newInstance(Const.NVL(name, ""), pluginId);
+      }
+      if (FQN_ACTION_FACTORY.equals(factoryName)) {
+        Class<?> c = Class.forName("org.apache.hop.workflow.actions.missing.MissingAction");
+        String actionName = (name == null || name.isEmpty()) ? null : name;
+        return c.getDeclaredConstructor(String.class, String.class)
+            .newInstance(actionName, pluginId);
+      }
+    } catch (Exception ignored) {
+      return null;
+    }
+    return null;
+  }
+
   /**
    * This method looks at the fields in the class of the provided parentObject. It then sees which
    * fields have annotation HopMetadataProperty and proceeds to serialize the values of those fields
@@ -816,6 +849,17 @@ private static <T> T createNewObject(Object parentObject, Node node, Class<? ext
             IHopMetadataObjectFactory factory =
                 metadataObject.objectFactory().getConstructor().newInstance();
             object = (T) factory.createObject(objectId, parentObject);
+          } catch (MissingResourceException e) {
+            Object placeholder = newMissingPluginPlaceholder(metadataObject, node, objectId);
+            if (placeholder == null) {
+              throw new HopXmlException(
+                  "Unable to create a new instance of class "
+                      + clazz.getName()
+                      + " while de-serializing XML: "
+                      + e.getMessage(),
+                  e);
+            }
+            object = (T) placeholder;
           } catch (HopMissingPluginsException e) {
             throw new HopXmlException(
                 "The plugin for class "

engine/src/main/java/org/apache/hop/pipeline/transforms/missing/MissingTransform.java

@@ -17,21 +17,26 @@
 
 package org.apache.hop.pipeline.transforms.missing;
 
+import org.apache.hop.core.exception.HopException;
 import org.apache.hop.i18n.BaseMessages;
 import org.apache.hop.pipeline.Pipeline;
 import org.apache.hop.pipeline.PipelineMeta;
+import org.apache.hop.pipeline.transform.BaseTransform;
 import org.apache.hop.pipeline.transform.TransformMeta;
-import org.apache.hop.pipeline.transforms.dummy.Dummy;
-import org.apache.hop.pipeline.transforms.dummy.DummyData;
-import org.apache.hop.pipeline.transforms.dummy.DummyMeta;
 
-public class MissingTransform extends Dummy {
+/**
+ * Runtime stand-in for a transform whose plugin is not installed. {@link Missing} declares {@code
+ * BaseTransformMeta<MissingTransform, MissingData>}, so {@link
+ * org.apache.hop.pipeline.transform.BaseTransformMeta#createTransform} must find a constructor
+ * {@code (TransformMeta, Missing, MissingData, int, PipelineMeta, Pipeline)}.
+ */
+public class MissingTransform extends BaseTransform<Missing, MissingData> {
   private static final Class<?> PKG = MissingTransform.class;
 
   public MissingTransform(
       TransformMeta transformMeta,
-      DummyMeta meta,
-      DummyData data,
+      Missing meta,
+      MissingData data,
       int copyNr,
       PipelineMeta pipelineMeta,
       Pipeline pipeline) {
@@ -45,4 +50,15 @@ public boolean init() {
     }
     return false;
   }
+
+  @Override
+  public boolean processRow() throws HopException {
+    Object[] r = getRow();
+    if (r == null) {
+      setOutputDone();
+      return false;
+    }
+    putRow(getInputRowMeta(), r);
+    return true;
+  }
 }

ui/src/main/java/org/apache/hop/ui/hopgui/file/pipeline/delegates/HopGuiPipelineTransformDelegate.java

@@ -49,6 +49,7 @@
 import org.apache.hop.pipeline.transform.TransformMeta;
 import org.apache.hop.pipeline.transform.TransformPartitioningMeta;
 import org.apache.hop.pipeline.transform.stream.IStream;
+import org.apache.hop.pipeline.transforms.missing.Missing;
 import org.apache.hop.ui.core.PropsUi;
 import org.apache.hop.ui.core.dialog.ErrorDialog;
 import org.apache.hop.ui.core.dialog.MessageBox;
@@ -61,6 +62,7 @@
 import org.apache.hop.ui.hopgui.partition.processor.IMethodProcessor;
 import org.apache.hop.ui.hopgui.partition.processor.MethodProcessorFactory;
 import org.apache.hop.ui.pipeline.transform.TransformErrorMetaDialog;
+import org.apache.hop.ui.pipeline.transforms.missing.MissingPipelineDialog;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Shell;
 
@@ -82,6 +84,15 @@ public ITransformDialog getTransformDialog(
       ITransformMeta transformMeta, PipelineMeta pipelineMeta, String transformName)
       throws HopException {
 
+    if (transformMeta instanceof Missing) {
+      return new MissingPipelineDialog(
+          hopGui.getShell(),
+          pipelineGraph.getVariables(),
+          transformMeta,
+          pipelineMeta,
+          transformName);
+    }
+
     PluginRegistry registry = PluginRegistry.getInstance();
     IPlugin plugin = registry.getPlugin(TransformPluginType.class, transformMeta);
     if (plugin == null) {

ui/src/main/java/org/apache/hop/ui/hopgui/file/workflow/delegates/HopGuiWorkflowActionDelegate.java

@@ -199,7 +199,7 @@ public IActionDialog getActionDialog(IAction action, WorkflowMeta workflowMeta)
     Object[] arguments =
         new Object[] {hopGui.getShell(), action, workflowMeta, workflowGraph.getVariables()};
 
-    if (MissingAction.ID.equals(action.getPluginId())) {
+    if (action instanceof MissingAction) {
       return new MissingActionDialog(
           hopGui.getActiveShell(), action, workflowMeta, workflowGraph.getVariables());
     }

ui/src/main/java/org/apache/hop/ui/hopgui/perspective/explorer/ExplorerPerspective.java

@@ -135,7 +135,6 @@
 import org.eclipse.swt.dnd.DropTargetEvent;
 import org.eclipse.swt.dnd.FileTransfer;
 import org.eclipse.swt.graphics.Font;
-import org.eclipse.swt.graphics.FontData;
 import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.graphics.Point;
@@ -569,7 +568,6 @@ protected void createTree(Composite parent) {
     tree.addListener(SWT.Selection, event -> updateSelection());
     tree.addListener(SWT.DefaultSelection, this::openFile);
     PropsUi.setLook(tree);
-    logFileExplorerFont("tree", tree.getFont());
 
     FormData treeFormData = new FormData();
     treeFormData.left = new FormAttachment(0, 0);
@@ -641,24 +639,6 @@ protected void createTree(Composite parent) {
     GuiRegistry.getInstance().executeCallbackMethods(GUI_CONTEXT_MENU_CREATED_CALLBACK_ID);
   }
 
-  private void logFileExplorerFont(String widget, Font font) {
-    if (font == null || font.isDisposed()) {
-      return;
-    }
-    FontData[] fda = font.getFontData();
-    if (fda != null && fda.length > 0) {
-      hopGui
-          .getLog()
-          .logBasic(
-              "File explorer "
-                  + widget
-                  + " font: family="
-                  + fda[0].getName()
-                  + ", size="
-                  + fda[0].getHeight());
-    }
-  }
-
   /**
    * Creates the Drag & Drop DragSource for items being dragged from the tree.
    *