handle empty flow match same way as if it was undefined

pkg/sdk/logging/api/v1beta1/syslogng_flow_types.go

@@ -39,6 +39,11 @@ type SyslogNGFlowSpec struct {
 
 type SyslogNGMatch filter.MatchExpr
 
+// IsEmpty returns true if the match is not specified, i.e. empty.
+func (m *SyslogNGMatch) IsEmpty() bool {
+	return (*filter.MatchExpr)(m).IsEmpty()
+}
+
 // Filter definition for SyslogNGFlowSpec
 type SyslogNGFilter struct {
 	ID      string                 `json:"id,omitempty" syslog-ng:"ignore"`

pkg/sdk/logging/model/syslogng/config/flow.go

@@ -20,11 +20,11 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/cisco-open/operator-tools/pkg/secret"
 	"github.com/kube-logging/logging-operator/pkg/sdk/logging/api/v1beta1"
 	"github.com/kube-logging/logging-operator/pkg/sdk/logging/model/syslogng/config/model"
 	"github.com/kube-logging/logging-operator/pkg/sdk/logging/model/syslogng/config/render"
 	filter "github.com/kube-logging/logging-operator/pkg/sdk/logging/model/syslogng/filter"
-	"github.com/cisco-open/operator-tools/pkg/secret"
 	"github.com/siliconbrain/go-seqs/seqs"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
@@ -42,7 +42,7 @@ func renderClusterFlow(sourceName string, f v1beta1.SyslogNGClusterFlow, secretL
 			[]string{sourceName},
 			seqs.ToSlice(seqs.Concat(
 				seqs.FromValues(
-					render.If(f.Spec.Match != nil, filterRefStmt(matchName)),
+					render.If(!f.Spec.Match.IsEmpty(), filterRefStmt(matchName)),
 				),
 				seqs.MapWithIndex(seqs.FromSlice(f.Spec.Filters), func(idx int, flt v1beta1.SyslogNGFilter) render.Renderer {
 					return parenDefStmt(filterKind(flt), render.Literal(filterID(flt, idx, baseName)))
@@ -88,7 +88,7 @@ func renderFlow(controlNS string, sourceName string, keyDelim string, f v1beta1.
 }
 
 func renderFlowMatch(name string, m *v1beta1.SyslogNGMatch) render.Renderer {
-	if m == nil {
+	if m.IsEmpty() {
 		return nil
 	}
 	return filterDefStmt(name, renderMatchExpr(filter.MatchExpr(*m)))

pkg/sdk/logging/model/syslogng/config/flow_test.go

@@ -0,0 +1,74 @@
+// Copyright © 2023 Kube logging authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kube-logging/logging-operator/pkg/sdk/logging/api/v1beta1"
+	"github.com/kube-logging/logging-operator/pkg/sdk/logging/model/syslogng/config/render"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestRenderClusterFlow(t *testing.T) {
+	testCases := map[string]struct {
+		clusterFlow v1beta1.SyslogNGClusterFlow
+		expected    string
+	}{
+		"nil match": {
+			clusterFlow: v1beta1.SyslogNGClusterFlow{
+				ObjectMeta: v1.ObjectMeta{
+					Name:      "test_clusterflow",
+					Namespace: "test_ns",
+				},
+				Spec: v1beta1.SyslogNGClusterFlowSpec{
+					Match: nil,
+				},
+			},
+			expected: Untab(`log {
+source("test_input");
+};
+`),
+		},
+		"empty match": {
+			clusterFlow: v1beta1.SyslogNGClusterFlow{
+				ObjectMeta: v1.ObjectMeta{
+					Name:      "test_clusterflow",
+					Namespace: "test_ns",
+				},
+				Spec: v1beta1.SyslogNGClusterFlowSpec{
+					Match: &v1beta1.SyslogNGMatch{},
+				},
+			},
+			expected: Untab(`log {
+source("test_input");
+};
+`),
+		},
+	}
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			out := strings.Builder{}
+			require.NoError(t, renderClusterFlow("test_input", testCase.clusterFlow, nil)(render.RenderContext{
+				Out: &out,
+			}))
+			assert.Equal(t, testCase.expected, out.String())
+		})
+	}
+}

pkg/sdk/logging/model/syslogng/filter/match.go

@@ -49,6 +49,11 @@ type _metaMatch interface{} //nolint:deadcode,unused
 // +kubebuilder:object:generate=true
 type MatchConfig MatchExpr
 
+// IsEmpty returns true if the config is not specified, i.e. empty.
+func (c *MatchConfig) IsEmpty() bool {
+	return (*MatchExpr)(c).IsEmpty()
+}
+
 // +kubebuilder:object:generate=true
 type MatchExpr struct {
 	// +kubebuilder:pruning:PreserveUnknownFields
@@ -64,6 +69,11 @@ type MatchExpr struct {
 	Or []MatchExpr `json:"or,omitempty"`
 }
 
+// IsEmpty returns true if the expression is not specified, i.e. empty.
+func (expr *MatchExpr) IsEmpty() bool {
+	return expr == nil || (len(expr.And) == 0 && expr.Not == nil && len(expr.Or) == 0 && expr.Regexp == nil)
+}
+
 // +kubebuilder:object:generate=true
 // +docName:"Regexp Directive"
 // Specify filtering rule. For details, see the [syslog-ng documentation](https://www.syslog-ng.com/technical-documents/doc/syslog-ng-open-source-edition/3.37/administration-guide/68#TOPIC-1829171).