Do not return null editor input from the ClassFileEditorInputFactory

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ClassFileEditorInputFactory.java

@@ -18,6 +18,7 @@
 
 import org.eclipse.ui.IElementFactory;
 import org.eclipse.ui.IMemento;
+import org.eclipse.ui.IPersistableElement;
 
 import org.eclipse.jdt.core.IClassFile;
 import org.eclipse.jdt.core.IJavaElement;
@@ -46,7 +47,18 @@ public ClassFileEditorInputFactory() {
 	public IAdaptable createElement(IMemento memento) {
 		String identifier= memento.getString(KEY);
 		if (identifier == null) {
-			return null;
+			return new ExceptionalEditorInput("memento data", new IPersistableElement() { //$NON-NLS-1$
+
+				@Override
+				public void saveState(IMemento m) {
+					//nothing to save...
+				}
+
+				@Override
+				public String getFactoryId() {
+					return ID;
+				}
+			}, new IllegalStateException(String.format("No %s present in memento", KEY))); //$NON-NLS-1$
 		}
 		IJavaElement element= JavaCore.create(identifier);
 		try {
@@ -60,15 +72,27 @@ public IAdaptable createElement(IMemento memento) {
 				IJavaProject project= element.getJavaProject();
 				if (project != null) {
 					type= project.findType(type.getFullyQualifiedName());
-					if (type == null)
-						return null;
-					element= type.getParent();
+					if (type != null) {
+						return EditorUtility.getEditorInput(type.getParent());
+					}
 				}
+				return new OrdinaryClassFileEditorInput(cf);
 			}
 			return EditorUtility.getEditorInput(element);
 		} catch (JavaModelException x) {
-			// Don't report but simply return null
-			return null;
+			return new ExceptionalEditorInput(identifier, new IPersistableElement() {
+
+				@Override
+				public void saveState(IMemento m) {
+					m.putString(KEY, identifier);
+
+				}
+
+				@Override
+				public String getFactoryId() {
+					return ID;
+				}
+			}, x);
 		}
 	}
 

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ExceptionalEditorInput.java

@@ -0,0 +1,79 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Christoph Läubrich and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Christoph Läubrich - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.jdt.internal.ui.javaeditor;
+
+import org.eclipse.jface.resource.ImageDescriptor;
+
+import org.eclipse.ui.IPersistableElement;
+
+import org.eclipse.jdt.core.IClassFile;
+import org.eclipse.jdt.core.JavaModelException;
+
+/**
+ * An editor input that is returned in case of an {@link JavaModelException} is thrown while trying to gather the actual input
+ */
+class ExceptionalEditorInput implements IClassFileEditorInput {
+
+
+	private String fIdentifier;
+	private Exception fException;
+	private IPersistableElement fElement;
+
+	public ExceptionalEditorInput(String identifier, IPersistableElement element, Exception modelException) {
+		fIdentifier= identifier;
+		fElement= element;
+		fException= modelException;
+	}
+
+	@Override
+	public boolean exists() {
+		return false;
+	}
+
+	@Override
+	public ImageDescriptor getImageDescriptor() {
+		return ImageDescriptor.getMissingImageDescriptor();
+	}
+
+	@Override
+	public String getName() {
+		return fIdentifier;
+	}
+
+	@Override
+	public IPersistableElement getPersistable() {
+		return fElement;
+	}
+
+	@Override
+	public String getToolTipText() {
+		return String.format("Error while gathering input for %s: %s", fIdentifier, fException); //$NON-NLS-1$
+	}
+
+	@Override
+	public <T> T getAdapter(Class<T> adapter) {
+		if (adapter == IPersistableElement.class) {
+			return adapter.cast(getPersistable());
+		}
+		return null;
+	}
+
+	@Override
+	public IClassFile getClassFile() {
+		if (fException instanceof RuntimeException rte) {
+			throw rte;
+		}
+		throw new RuntimeException(getToolTipText(), fException);
+	}
+}

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/OrdinaryClassFileEditorInput.java

@@ -0,0 +1,29 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Christoph Läubrich and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Christoph Läubrich - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.jdt.internal.ui.javaeditor;
+
+import org.eclipse.jdt.core.IOrdinaryClassFile;
+
+public class OrdinaryClassFileEditorInput extends InternalClassFileEditorInput {
+
+	public OrdinaryClassFileEditorInput(IOrdinaryClassFile classFile) {
+		super(classFile);
+	}
+
+	@Override
+	public IOrdinaryClassFile getClassFile() {
+		return (IOrdinaryClassFile) super.getClassFile();
+	}
+
+}