api: drop MergeBackendsConfig.Enabled, presence alone enables MergeBackends

Mirrors the existing MergeGateways *bool precedent: mergeBackends being
set at all (even empty) now enables cluster deduplication, so there is
no separate on/off toggle to get out of sync with field presence. This
also simplifies the mergeGateways/mergeBackends mutual-exclusion CEL
rule to a presence check.

Signed-off-by: Muhammad Waqar <mwaqar@confluent.io>

Author: muwaqar-cflt

api/v1alpha1/envoyproxy_types.go

@@ -35,7 +35,7 @@ type EnvoyProxy struct {
 }
 
 // EnvoyProxySpec defines the desired state of EnvoyProxy.
-// +kubebuilder:validation:XValidation:message="mergeGateways and mergeBackends cannot both be enabled",rule="!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends) && has(self.mergeBackends.enabled) && self.mergeBackends.enabled)"
+// +kubebuilder:validation:XValidation:message="mergeGateways and mergeBackends cannot both be enabled",rule="!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends))"
 type EnvoyProxySpec struct {
 	// Provider defines the desired resource provider and provider-specific configuration.
 	// If unspecified, the "Kubernetes" resource provider is used with default configuration
@@ -100,7 +100,8 @@ type EnvoyProxySpec struct {
 	// rule. This reduces xDS size, active health-check traffic, and stats cardinality, and
 	// improves upstream connection pooling.
 	//
-	// Disabled when unset. Mutually exclusive with MergeGateways.
+	// Disabled when unset; specifying this field at all (even without further configuration)
+	// enables it. Mutually exclusive with MergeGateways.
 	//
 	// +optional
 	MergeBackends *MergeBackendsConfig `json:"mergeBackends,omitempty"`
@@ -231,17 +232,10 @@ type EnvoyProxySpec struct {
 	MergeType *MergeType `json:"mergeType,omitempty"`
 }
 
-// MergeBackendsConfig configures backend cluster deduplication (MergeBackends).
-type MergeBackendsConfig struct {
-	// Enabled toggles whether cluster deduplication is considered at all. Defaults to false.
-	//
-	// A backendRef is only merged into a shared cluster when safe to do so; otherwise it falls
-	// back to a dedicated per-route cluster.
-	//
-	// +optional
-	// +kubebuilder:default=false
-	Enabled *bool `json:"enabled,omitempty"`
-}
+// MergeBackendsConfig configures backend cluster deduplication (MergeBackends). Its mere
+// presence on EnvoyProxySpec enables it; a backendRef is only merged into a shared cluster when
+// safe to do so, otherwise it falls back to a dedicated per-route cluster.
+type MergeBackendsConfig struct{}
 
 // EnvoyProxyGeoIP defines shared GeoIP provider settings for EnvoyProxy.
 type EnvoyProxyGeoIP struct {

api/v1alpha1/zz_generated.deepcopy.go

@@ -785,16 +785,8 @@ spec:
                   rule. This reduces xDS size, active health-check traffic, and stats cardinality, and
                   improves upstream connection pooling.
 
-                  Disabled when unset. Mutually exclusive with MergeGateways.
-                properties:
-                  enabled:
-                    default: false
-                    description: |-
-                      Enabled toggles whether cluster deduplication is considered at all. Defaults to false.
-
-                      A backendRef is only merged into a shared cluster when safe to do so; otherwise it falls
-                      back to a dedicated per-route cluster.
-                    type: boolean
+                  Disabled when unset; specifying this field at all (even without further configuration)
+                  enables it. Mutually exclusive with MergeGateways.
                 type: object
               mergeGateways:
                 description: |-
@@ -18134,8 +18126,7 @@ spec:
             type: object
             x-kubernetes-validations:
             - message: mergeGateways and mergeBackends cannot both be enabled
-              rule: '!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends)
-                && has(self.mergeBackends.enabled) && self.mergeBackends.enabled)'
+              rule: '!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends))'
           status:
             description: EnvoyProxyStatus defines the actual state of EnvoyProxy.
             properties:

charts/gateway-crds-helm/templates/generated/gateway.envoyproxy.io_envoyproxies.yaml

@@ -784,16 +784,8 @@ spec:
                   rule. This reduces xDS size, active health-check traffic, and stats cardinality, and
                   improves upstream connection pooling.
 
-                  Disabled when unset. Mutually exclusive with MergeGateways.
-                properties:
-                  enabled:
-                    default: false
-                    description: |-
-                      Enabled toggles whether cluster deduplication is considered at all. Defaults to false.
-
-                      A backendRef is only merged into a shared cluster when safe to do so; otherwise it falls
-                      back to a dedicated per-route cluster.
-                    type: boolean
+                  Disabled when unset; specifying this field at all (even without further configuration)
+                  enables it. Mutually exclusive with MergeGateways.
                 type: object
               mergeGateways:
                 description: |-
@@ -18133,8 +18125,7 @@ spec:
             type: object
             x-kubernetes-validations:
             - message: mergeGateways and mergeBackends cannot both be enabled
-              rule: '!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends)
-                && has(self.mergeBackends.enabled) && self.mergeBackends.enabled)'
+              rule: '!(has(self.mergeGateways) && self.mergeGateways && has(self.mergeBackends))'
           status:
             description: EnvoyProxyStatus defines the actual state of EnvoyProxy.
             properties:

charts/gateway-helm/charts/crds/crds/generated/gateway.envoyproxy.io_envoyproxies.yaml

@@ -702,13 +702,12 @@ func IsMergeBackendsEnabled(resources *resource.Resources) bool {
 	// Check GatewayClass-level EnvoyProxy first (higher priority)
 	if resources.EnvoyProxyForGatewayClass != nil &&
 		resources.EnvoyProxyForGatewayClass.Spec.MergeBackends != nil {
-		return ptr.Deref(resources.EnvoyProxyForGatewayClass.Spec.MergeBackends.Enabled, false)
+		return true
 	}
 
 	// Fall back to default EnvoyProxySpec from EnvoyGateway configuration
-	if resources.EnvoyProxyDefaultSpec != nil &&
-		resources.EnvoyProxyDefaultSpec.MergeBackends != nil {
-		return ptr.Deref(resources.EnvoyProxyDefaultSpec.MergeBackends.Enabled, false)
+	if resources.EnvoyProxyDefaultSpec != nil {
+		return resources.EnvoyProxyDefaultSpec.MergeBackends != nil
 	}
 
 	return false

internal/gatewayapi/helpers.go

@@ -1608,8 +1608,7 @@ func TestIrBackendClusterName(t *testing.T) {
 }
 
 func TestIsMergeBackendsEnabled(t *testing.T) {
-	enabled := &egv1a1.MergeBackendsConfig{Enabled: new(true)}
-	disabled := &egv1a1.MergeBackendsConfig{Enabled: new(false)}
+	enabled := &egv1a1.MergeBackendsConfig{}
 
 	tests := []struct {
 		name string
@@ -1630,14 +1629,6 @@ func TestIsMergeBackendsEnabled(t *testing.T) {
 			},
 			want: true,
 		},
-		{
-			name: "gatewayclass envoyproxy takes precedence over default spec",
-			res: &resource.Resources{
-				EnvoyProxyForGatewayClass: &egv1a1.EnvoyProxy{Spec: egv1a1.EnvoyProxySpec{MergeBackends: disabled}},
-				EnvoyProxyDefaultSpec:     &egv1a1.EnvoyProxySpec{MergeBackends: enabled},
-			},
-			want: false,
-		},
 		{
 			name: "gatewayclass envoyproxy set but MergeBackends nil falls back to default spec",
 			res: &resource.Resources{

internal/gatewayapi/helpers_test.go

@@ -582,7 +582,7 @@ func (t *Translator) shouldMergeBackend(
 // override (via gatewayCtx.envoyProxy) win over t.MergeBackends' GatewayClass/default value.
 func (t *Translator) isMergeBackendsEnabledForGateway(gatewayCtx *GatewayContext) bool {
 	if gatewayCtx != nil && gatewayCtx.envoyProxy != nil && gatewayCtx.envoyProxy.Spec.MergeBackends != nil {
-		return ptr.Deref(gatewayCtx.envoyProxy.Spec.MergeBackends.Enabled, false)
+		return true
 	}
 	return t.MergeBackends
 }

internal/gatewayapi/route.go

@@ -610,20 +610,11 @@ func TestShouldMergeBackend(t *testing.T) {
 			name:         "disabled globally, but Gateway-level EnvoyProxy enables it",
 			mergeEnabled: false,
 			gatewayEnvoyProxy: &egv1a1.EnvoyProxy{
-				Spec: egv1a1.EnvoyProxySpec{MergeBackends: &egv1a1.MergeBackendsConfig{Enabled: new(true)}},
+				Spec: egv1a1.EnvoyProxySpec{MergeBackends: &egv1a1.MergeBackendsConfig{}},
 			},
 			backendRef: serviceBackendRef,
 			want:       true,
 		},
-		{
-			name:         "enabled globally, but Gateway-level EnvoyProxy disables it",
-			mergeEnabled: true,
-			gatewayEnvoyProxy: &egv1a1.EnvoyProxy{
-				Spec: egv1a1.EnvoyProxySpec{MergeBackends: &egv1a1.MergeBackendsConfig{Enabled: new(false)}},
-			},
-			backendRef: serviceBackendRef,
-			want:       false,
-		},
 		{
 			name:         "enabled, no routing type anywhere: baseline == effective (both Endpoint)",
 			mergeEnabled: true,

internal/gatewayapi/route_test.go

@@ -7,8 +7,7 @@ envoyProxyForGatewayClass:
   spec:
     mergeGateways: true
 envoyProxyDefaultSpec:
-  mergeBackends:
-    enabled: true
+  mergeBackends: {}
 gateways:
   - apiVersion: gateway.networking.k8s.io/v1
     kind: Gateway

internal/gatewayapi/testdata/mergebackends-gateway-mergegateways-conflict.in.yaml

@@ -5,8 +5,7 @@ envoyProxyForGatewayClass:
     namespace: envoy-gateway-system
     name: test
   spec:
-    mergeBackends:
-      enabled: true
+    mergeBackends: {}
 gateways:
   - apiVersion: gateway.networking.k8s.io/v1
     kind: Gateway