EvenPodsSpread: api changes

pkg/api/pod/util.go

@@ -401,6 +401,11 @@ func dropDisabledFields(
 		// does not specify any values for these fields.
 		podSpec.PreemptionPolicy = nil
 	}
+
+	if !utilfeature.DefaultFeatureGate.Enabled(features.EvenPodsSpread) && !topologySpreadConstraintsInUse(oldPodSpec) {
+		// Set TopologySpreadConstraints to nil only if feature is disabled and it is not used
+		podSpec.TopologySpreadConstraints = nil
+	}
 }
 
 // dropDisabledRunAsGroupField removes disabled fields from PodSpec related
@@ -562,7 +567,14 @@ func overheadInUse(podSpec *api.PodSpec) bool {
 		return true
 	}
 	return false
+}
 
+// topologySpreadConstraintsInUse returns true if the pod spec is non-nil and has a TopologySpreadConstraints slice
+func topologySpreadConstraintsInUse(podSpec *api.PodSpec) bool {
+	if podSpec == nil {
+		return false
+	}
+	return len(podSpec.TopologySpreadConstraints) > 0
 }
 
 // procMountInUse returns true if the pod spec is non-nil and has a SecurityContext's ProcMount field set to a non-default value