re-enable action groups when their children become visible

platform/lang-impl/src/com/intellij/codeInsight/completion/actions/CodeCompletionGroup.java

@@ -47,4 +47,9 @@ public class CodeCompletionGroup extends DefaultActionGroup implements DumbAware
 
     presentation.setEnabled(true);
   }
+
+  @Override
+  public boolean disableIfNoVisibleChildren() {
+    return false;
+  }
 }

platform/platform-api/src/com/intellij/openapi/actionSystem/ActionGroup.java

@@ -188,4 +188,8 @@ public abstract class ActionGroup extends AnAction {
   public boolean hideIfNoVisibleChildren() {
     return false;
   }
+
+  public boolean disableIfNoVisibleChildren() {
+    return true;
+  }
 }

platform/platform-impl/src/com/intellij/openapi/actionSystem/impl/Utils.java

@@ -130,14 +130,14 @@ public class Utils{
       if (child instanceof ActionGroup) {
         ActionGroup actionGroup = (ActionGroup)child;
         if (actionGroup.isPopup()) { // popup menu has its own presentation
-          // disable group if it contains no visible actions
-          final boolean visibleChildren = hasVisibleChildren(actionGroup, presentationFactory, context, place);
-          if (actionGroup.hideIfNoVisibleChildren() && !visibleChildren) {
-            continue;
-          }
-          if (!actionGroup.canBePerformed(context) && !visibleChildren) {
-            presentation.setEnabled(false);
+          if (actionGroup.disableIfNoVisibleChildren()) {
+            final boolean visibleChildren = hasVisibleChildren(actionGroup, presentationFactory, context, place);
+            if (actionGroup.hideIfNoVisibleChildren() && !visibleChildren) {
+              continue;
+            }
+            presentation.setEnabled(actionGroup.canBePerformed(context) || visibleChildren);
           }
+
           list.add(child);
         }
         else {