From f9046e6ec422d5d2d9e8a7603ebe7171a9f4c560 Mon Sep 17 00:00:00 2001
From: Henry Weller <http://cfd.direct>
Date: Mon, 8 Apr 2024 12:50:26 +0100
Subject: [PATCH] ZoneList: Empty ZoneLists are no longer written

---
 src/OpenFOAM/meshes/zones/ZoneList/ZoneList.C | 20 +++++++++++++++++++
 src/OpenFOAM/meshes/zones/ZoneList/ZoneList.H | 12 ++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.C b/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.C
index 82b6fa7ec1..a8f8d3f6e3 100644
--- a/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.C
+++ b/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.C
@@ -492,6 +492,26 @@ bool Foam::ZoneList<ZoneType, ZonesType, MeshType>::writeData(Ostream& os) const
 }
 
 
+template<class ZoneType, class ZonesType, class MeshType>
+bool Foam::ZoneList<ZoneType, ZonesType, MeshType>::writeObject
+(
+    IOstream::streamFormat fmt,
+    IOstream::versionNumber ver,
+    IOstream::compressionType cmp,
+    const bool write
+) const
+{
+    if (this->size())
+    {
+        return regIOobject::writeObject(fmt, ver, cmp, write);
+    }
+    else
+    {
+        return false;
+    }
+}
+
+
 // * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
 
 template<class ZoneType, class ZonesType, class MeshType>
diff --git a/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.H b/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.H
index 74f2a7e812..31d967bf6d 100644
--- a/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.H
+++ b/src/OpenFOAM/meshes/zones/ZoneList/ZoneList.H
@@ -165,7 +165,17 @@ public:
         bool readIfPresent();
 
         //- writeData member function required by regIOobject
-        bool writeData(Ostream&) const;
+        virtual bool writeData(Ostream&) const;
+
+        //- Write using given format, version and compression
+        //  Only write the zones file if there are zones in the list
+        virtual bool writeObject
+        (
+            IOstream::streamFormat,
+            IOstream::versionNumber,
+            IOstream::compressionType,
+            const bool write
+        ) const;
 
 
     // Member Operators