Sonar tag for skipping empty view groups in layout target mode

Summary:
I think it's somewhat common to have large containers that can hold future views, especially fragments. The problem is the presence of these containers can block the layout inspector's "target" mode.

I found out from cekkaewnumchai that Flipper does in fact return multiple results from the pick, but I think it could still be helpful to have this new tag since it is more convenient than having to do the secondary drill down each time.

Reviewed By: jknoxville

Differential Revision: D22284972

fbshipit-source-id: 1a2826ec746e4f31690db33ed72815ae168bffab

android/src/main/java/com/facebook/flipper/plugins/inspector/descriptors/ViewGroupDescriptor.java

@@ -294,12 +294,31 @@ public class ViewGroupDescriptor extends NodeDescriptor<ViewGroup> {
   }
 
   private static boolean shouldSkip(View view) {
-    Object tag = view.getTag(R.id.flipper_skip_view_traversal);
-    if (!(tag instanceof Boolean)) {
-      return false;
+    if (hasTag(view, R.id.flipper_skip_view_traversal)) {
+      return true;
     }
 
-    return (Boolean) tag;
+    if (view instanceof ViewGroup
+        && hasTag(view, R.id.flipper_skip_empty_view_group_traversal)
+        && !hasVisibleChildren((ViewGroup) view)) {
+      return true;
+    }
+
+    return false;
+  }
+
+  private static boolean hasTag(View view, int id) {
+    Object tag = view.getTag(id);
+    return tag instanceof Boolean && (Boolean) tag;
+  }
+
+  private static boolean hasVisibleChildren(ViewGroup viewGroup) {
+    for (int i = 0; i < viewGroup.getChildCount(); i++) {
+      if (viewGroup.getChildAt(i).getVisibility() == View.VISIBLE) {
+        return true;
+      }
+    }
+    return false;
   }
 
   @Override

android/src/main/res/values/ids.xml

@@ -8,4 +8,5 @@
 
 <resources>
   <item type="id" name="flipper_skip_view_traversal"/>
+  <item type="id" name="flipper_skip_empty_view_group_traversal"/>
 </resources>

docs/setup/layout-plugin.mdx

@@ -66,6 +66,15 @@ Add the following tag to your view to skip it from Flipper's view picker. The vi
 view.setTag(R.id.flipper_skip_view_traversal, true);
 ```
 
+### Blocking empty view groups (Android only)
+
+If you have a ViewGroup that only occasionally has visible children, you may find it helpful to block its traversal when it is empty or has no visible children. For example, you might have a FragmentContainerView that currently has no visible fragment.
+
+Add the following tag to your view group to skip it from Flipper's view picker only when it has zero children, or none of its children are currently visible. The views will still be shown in the layout hierarchy, but they will not be selected while using the view picker.
+
+```java
+viewGroup.setTag(R.id.flipper_skip_empty_view_group_traversal, true);
+```
 
 ## iOS