Defer expensive project reference computation during selection changes

CloseUnrelatedProjectsAction.getSelectedResources() calls
computeRelated() which triggers buildConnectedComponents() and
getReferencedProjects() for every project in the workspace. This is
expensive because it can trigger classpath container resolution.

Previously, the inherited updateSelection() called getSelectedResources()
on every selection change, causing this expensive computation to run on
the UI thread during startup and navigation. This blocked the IDE.

Override updateSelection() to perform only a cheap enablement check:
verify the selection contains at least one open IProject. The expensive
computeRelated() call is deferred to getSelectedResources(), which is
only invoked when the action is actually executed via run(). This is
correct because getSelectedResources() already handles the selectionDirty
flag and recomputes projectsToClose lazily when needed.

Fixes #2636

Author: vogella

bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java

@@ -30,6 +30,7 @@
 import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.dialogs.MessageDialogWithToggle;
 import org.eclipse.jface.preference.IPreferenceStore;
+import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.jface.window.IShellProvider;
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.swt.widgets.Shell;
@@ -130,6 +131,25 @@ public CloseUnrelatedProjectsAction(IShellProvider provider){
 		initAction();
 	}
 
+	/**
+	 * Overrides to avoid calling the expensive
+	 * {@link #computeRelated(List)} during selection changes. Uses only
+	 * the raw selection to determine enablement.
+	 */
+	@Override
+	protected boolean updateSelection(IStructuredSelection s) {
+		selectionDirty = true;
+		if (!selectionIsOfType(IResource.PROJECT)) {
+			return false;
+		}
+		for (IResource resource : super.getSelectedResources()) {
+			if (resource instanceof IProject project && project.isOpen()) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	@Override
 	public void run() {
 		if (promptForConfirmation()) {