Honor Java Expression's context when creating Watches

When selecting a field under an object, both the Watch command and Drag
& Drop previously created a non-contextual expression using only the
field name, which caused evaluation failures. This fix ensures that both
Watch and Drag & Drop now generate proper context-aware expressions such
as myobj.myfield instead of just the field name.

Platform changes :
eclipse-platform/eclipse.platform#2311

Fixes : https://bugs.eclipse.org/bugs/show_bug.cgi?id=321289

Author: SougandhS

org.eclipse.jdt.debug.tests/testprograms/WatchItemContext.java

@@ -0,0 +1,44 @@
+/*******************************************************************************
+ * Copyright (c) 2026 IBM Corporation.
+ *
+ * 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:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+
+/**
+ * WatchItemContext
+ */
+public class WatchItemContext {
+
+	private class X {
+		private int x = 0;
+	}
+
+	private class Y {
+		private X x = new X();
+		private int y = 0;
+	}
+
+	private class Z {
+		private Y y = new Y();
+		private int z = 0;
+	}
+
+	public static void main(String[] args) {
+		new WatchItemContext().foo();
+	}
+
+	public void foo() {
+		X x = new X();
+		Y y = new Y();
+		Z z = new Z();
+		System.out.println(x + " " + y + " " + z);
+	}
+}

org.eclipse.jdt.debug.tests/tests/org/eclipse/jdt/debug/tests/AbstractDebugTest.java

@@ -219,7 +219,7 @@ public abstract class AbstractDebugTest extends TestCase implements  IEvaluation
 			"OutSync", "OutSync2", "ConsoleOutputUmlaut", "ErrorRecurrence", "ModelPresentationTests", "Bug565982",
 			"SuspendVMConditionalBreakpointsTestSnippet", "FileConditionSnippet2", "compare.CompareObjectsStringTest", "compare.CompareListObjects",
 			"compare.CompareMapObjects", "compare.CompareSetObjects", "compare.CompareNormalObjects", "compare.CompareArrayObjects",
-			"StatementStep", "StatementStepArgument", "StatementStepNested", "StatementStepWithOperations" };
+			"StatementStep", "StatementStepArgument", "StatementStepNested", "StatementStepWithOperations", "WatchItemContext" };
 
 	/**
 	 * the default timeout

org.eclipse.jdt.debug.tests/tests/org/eclipse/jdt/debug/tests/core/WatchExpressionTests.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2015 IBM Corporation and others.
+ * Copyright (c) 2000, 2026 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -13,10 +13,13 @@
  *******************************************************************************/
 package org.eclipse.jdt.debug.tests.core;
 
+import java.util.List;
+
 import org.eclipse.debug.core.DebugEvent;
 import org.eclipse.debug.core.DebugPlugin;
 import org.eclipse.debug.core.IExpressionManager;
 import org.eclipse.debug.core.model.IValue;
+import org.eclipse.debug.core.model.IVariable;
 import org.eclipse.debug.core.model.IWatchExpression;
 import org.eclipse.debug.internal.ui.DebugUIPlugin;
 import org.eclipse.debug.ui.IDebugUIConstants;
@@ -27,6 +30,7 @@
 import org.eclipse.jdt.debug.testplugin.DebugElementEventWaiter;
 import org.eclipse.jdt.debug.testplugin.ExpressionWaiter;
 import org.eclipse.jdt.debug.tests.AbstractDebugTest;
+import org.eclipse.jdt.internal.debug.ui.heapwalking.JavaNestedWatchExpressionFilter;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.ui.IWorkbench;
 import org.eclipse.ui.IWorkbenchPage;
@@ -165,6 +169,32 @@ public void DisabledtestStepping() throws Exception {
 		}
 	}
 
+	public void testExpressionContext() throws Exception {
+		String typeName = "WatchItemContext";
+		createLineBreakpoint(42, typeName);
+		IJavaThread thread = null;
+		try {
+			thread = launchToBreakpoint(typeName);
+			assertNotNull("Breakpoint not hit within timeout period", thread);
+			IJavaStackFrame stackFrame = (IJavaStackFrame) thread.getTopStackFrame();
+			IVariable v1 = stackFrame.findVariable("y");
+			IVariable v2 = v1.getValue().getVariables()[2];
+			JavaNestedWatchExpressionFilter javaFilter = new JavaNestedWatchExpressionFilter();
+			assertTrue(javaFilter.canCreateWatchExpression(List.of(v1, v2)));
+			String exp = javaFilter.createWatchExpression(List.of(v1, v2));
+			assertEquals("Invalid Expression", "y.y", exp);
+			IWatchExpression expression = getExpressionManager().newWatchExpression(exp);
+			DebugElementEventWaiter waiter = new ExpressionWaiter(DebugEvent.CHANGE, expression);
+			getExpressionManager().addExpression(expression);
+			waiter.waitForEvent();
+			assertEquals("Wrong Value", "0", expression.getValue().toString());
+		} finally {
+			terminateAndRemove(thread);
+			removeAllBreakpoints();
+			removeAllExpressions();
+		}
+	}
+
 	/**
 	 * Dumps any error messages to the console.
      */

org.eclipse.jdt.debug.ui/ui/org/eclipse/jdt/internal/debug/ui/heapwalking/JavaNestedWatchExpressionFilter.java

@@ -0,0 +1,91 @@
+/*******************************************************************************
+ * Copyright (c) 2026 IBM Corporation.
+ *
+ * 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:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.jdt.internal.debug.ui.heapwalking;
+
+import java.util.List;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.debug.core.DebugException;
+import org.eclipse.debug.core.model.IVariable;
+import org.eclipse.debug.internal.ui.views.variables.IndexedVariablePartition;
+import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapter2;
+import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapterExtension;
+import org.eclipse.jdt.internal.debug.core.logicalstructures.JDIPlaceholderVariable;
+import org.eclipse.jdt.internal.debug.core.model.JDIArrayEntryVariable;
+import org.eclipse.jdt.internal.debug.core.model.JDIPlaceholderValue;
+import org.eclipse.jdt.internal.debug.core.model.JDIReferenceListEntryVariable;
+import org.eclipse.jdt.internal.debug.core.model.JDIReferenceListVariable;
+
+/**
+ * Uses the {@link IWatchExpressionFactoryAdapterExtension} to filter when the watch expression action is available based on the variable selected.
+ *
+ * Currently removes the action from {@link JDIPlaceholderVariable}s and {@link JDIReferenceListVariable}s.
+ */
+public class JavaNestedWatchExpressionFilter implements IWatchExpressionFactoryAdapter2 {
+
+	@Override
+	public String createWatchExpression(Object element) throws CoreException {
+		if (element instanceof List<?> expVariablesList) {
+			StringBuilder expresion = new StringBuilder();
+			for (Object ob : expVariablesList) {
+				if (ob instanceof IVariable variable) {
+					String current = variable.getName();
+					expresion.append(current);
+					expresion.append('.');
+				}
+			}
+			expresion.deleteCharAt(expresion.length() - 1);
+			return expresion.toString();
+		}
+		return null;
+	}
+
+	@Override
+	public boolean canCreateWatchExpression(Object variable) {
+		if (variable instanceof List<?> expVariablesList) {
+			for (Object ob : expVariablesList) {
+				if (ob instanceof IVariable variable2) {
+					return checkForValidVariable(variable2);
+				}
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Checks whether the given {@link IVariable} is suitable for creating a watch expression.
+	 * <p>
+	 * Filters out variables that represent internal or synthetic structures (such as reference lists, array entries, indexed partitions) or
+	 * placeholder values that do not have a concrete value.
+	 * </p>
+	 *
+	 * @param variable
+	 *            the variable to check
+	 * @return {@code true} if the variable can be used to create a watch expression, {@code false} otherwise
+	 */
+	private boolean checkForValidVariable(IVariable variable) {
+		if (variable instanceof JDIReferenceListVariable || variable instanceof JDIReferenceListEntryVariable
+				|| variable instanceof JDIArrayEntryVariable || variable instanceof IndexedVariablePartition) {
+			return false;
+		}
+		try {
+			if (variable.getValue() instanceof JDIPlaceholderValue) {
+				return false;
+			}
+		} catch (DebugException e) {
+		}
+		return true;
+	}
+
+}

org.eclipse.jdt.debug.ui/ui/org/eclipse/jdt/internal/debug/ui/variables/JavaDebugElementAdapterFactory.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2006, 2015 IBM Corporation and others.
+ * Copyright (c) 2006, 2026 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -19,10 +19,12 @@
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IElementLabelProvider;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IElementMementoProvider;
 import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapter;
+import org.eclipse.debug.ui.actions.IWatchExpressionFactoryAdapter2;
 import org.eclipse.jdt.debug.core.IJavaStackFrame;
 import org.eclipse.jdt.debug.core.IJavaValue;
 import org.eclipse.jdt.debug.core.IJavaVariable;
 import org.eclipse.jdt.internal.debug.ui.display.JavaInspectExpression;
+import org.eclipse.jdt.internal.debug.ui.heapwalking.JavaNestedWatchExpressionFilter;
 import org.eclipse.jdt.internal.debug.ui.heapwalking.JavaWatchExpressionFilter;
 
 /**
@@ -33,6 +35,7 @@
  * @see JavaVariableContentProvider
  * @see ExpressionLabelProvider
  * @see JavaExpressionContentProvider
+ * @see JavaNestedWatchExpressionFilter
  * @see JavaWatchExpressionFilter
  * @see JavaStackFrameMementoProvider
  * @since 3.3
@@ -44,6 +47,7 @@ public class JavaDebugElementAdapterFactory implements IAdapterFactory {
 	private static final IElementLabelProvider fgLPExpression = new ExpressionLabelProvider();
 	private static final IElementContentProvider fgCPExpression = new JavaExpressionContentProvider();
 	private static final IWatchExpressionFactoryAdapter fgWEVariable = new JavaWatchExpressionFilter();
+	private static final IWatchExpressionFactoryAdapter2 NestedWatchExpressionsAdapter = new JavaNestedWatchExpressionFilter();
 	private static final IElementMementoProvider fgMPStackFrame = new JavaStackFrameMementoProvider();
 	private static final IElementLabelProvider fgLPFrame = new JavaStackFrameLabelProvider();
 
@@ -83,6 +87,14 @@ public <T> T getAdapter(Object adaptableObject, Class<T> adapterType) {
 				return (T) fgWEVariable;
 			}
 		}
+		if (IWatchExpressionFactoryAdapter2.class.equals(adapterType)) {
+			if (adaptableObject instanceof IJavaVariable) {
+				return (T) NestedWatchExpressionsAdapter;
+			}
+			if (adaptableObject instanceof JavaInspectExpression) {
+				return (T) NestedWatchExpressionsAdapter;
+			}
+		}
 		if (IElementMementoProvider.class.equals(adapterType)) {
 			if (adaptableObject instanceof IJavaStackFrame) {
 				return (T) fgMPStackFrame;
@@ -96,6 +108,7 @@ public <T> T getAdapter(Object adaptableObject, Class<T> adapterType) {
 	 */
 	@Override
 	public Class<?>[] getAdapterList() {
-		return new Class[] {IElementLabelProvider.class, IElementContentProvider.class, IWatchExpressionFactoryAdapter.class, IElementMementoProvider.class};
+		return new Class[] { IElementLabelProvider.class, IElementContentProvider.class, IWatchExpressionFactoryAdapter.class,
+				IWatchExpressionFactoryAdapter2.class, IElementMementoProvider.class };
 	}
 }