override unmarshalJSON for supportedfeature to ensure comptability (#3454)

* override json unmarshal for supportedfeature to ensure backward compatability

* add issue link

Author: LiorLieberman

apis/v1/gatewayclass_types_overrides.go

@@ -0,0 +1,59 @@
+/*
+Copyright 2024 The Kubernetes 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 v1
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+// Below code handles the experimental field breaking change introduced in
+// https://github.com/kubernetes-sigs/gateway-api/pull/3200/.
+// We are overriding the UnmarshalJSON function to be able to handle cases where
+// users had the old version of the GatewayClass CRD applied with SupportedFeatures
+// as a list of strings and not list of objects.
+// See https://github.com/kubernetes-sigs/gateway-api/issues/3464
+// for more information.
+
+func (s *SupportedFeature) UnmarshalJSON(data []byte) error {
+	var oldSupportedFeature oldSupportedFeature
+	var unmarshalTypeErr *json.UnmarshalTypeError
+	if err := json.Unmarshal(data, &oldSupportedFeature); err == nil {
+		s.Name = FeatureName(oldSupportedFeature)
+		return nil
+	} else if !errors.As(err, &unmarshalTypeErr) {
+		// If the error is not a type error, return it
+		return err
+	}
+
+	var si supportedFeatureInternal
+	if err := json.Unmarshal(data, &si); err != nil {
+		return err
+	}
+	s.Name = si.Name
+	return nil
+}
+
+// This is solely for the purpose of ensuring backward compatibility and
+// SHOULD NOT be used elsewhere.
+type supportedFeatureInternal struct {
+	Name FeatureName `json:"name"`
+}
+
+// This is solely for the purpose of ensuring backward compatibility and
+// SHOULD NOT be used elsewhere.
+type oldSupportedFeature string

apis/v1/gatewayclass_types_test.go

@@ -0,0 +1,67 @@
+/*
+Copyright 2024 The Kubernetes 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 v1
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestSupportedFeature_UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name        string
+		input       string
+		expected    SupportedFeature
+		expectError bool
+	}{
+		{
+			name:     "old struct input",
+			input:    `"featureA"`,
+			expected: SupportedFeature{Name: "featureA"},
+		},
+		{
+			name:     "new struct input",
+			input:    `{"name": "featureB"}`,
+			expected: SupportedFeature{Name: "featureB"},
+		},
+		{
+			name:        "expected error",
+			input:       `["featureA", "featureB"]`,
+			expectError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var result SupportedFeature
+			err := json.Unmarshal([]byte(tt.input), &result)
+
+			if tt.expectError {
+				if err == nil {
+					t.Errorf("Expected an error, but got nil")
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Unexpected error: %v", err)
+				}
+				if result != tt.expected {
+					t.Errorf("Expected %+v, got %+v", tt.expected, result)
+				}
+			}
+		})
+	}
+}