[FLINK-37406] Fix config array serialization

Author: csviri

flink-kubernetes-operator-api/src/main/java/org/apache/flink/kubernetes/operator/api/spec/ConfigObjectNode.java

@@ -20,12 +20,15 @@
 import org.apache.flink.configuration.Configuration;
 
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 
 /** Allows parsing configurations as YAML, and adds related utility methods. */
@@ -78,12 +81,26 @@ private static void flattenHelper(
             }
         } else if (node.isArray()) {
             for (int i = 0; i < node.size(); i++) {
-                String newKey = parentKey + "[" + i + "]";
-                flattenHelper(node.get(i), newKey, flatMap);
+                if (node instanceof ArrayNode) {
+                    flatMap.put(parentKey, arrayNodeToSemicolonSepratedString((ArrayNode) node));
+                } else {
+                    String newKey = parentKey + "[" + i + "]";
+                    flattenHelper(node.get(i), newKey, flatMap);
+                }
             }
         } else {
-            // Store values as strings
             flatMap.put(parentKey, node.asText());
         }
     }
+
+    private static String arrayNodeToSemicolonSepratedString(ArrayNode arrayNode) {
+        if (arrayNode == null || arrayNode.isEmpty()) {
+            return "";
+        }
+        List<String> stringValues = new ArrayList<>();
+        for (JsonNode node : arrayNode) {
+            stringValues.add(node.asText());
+        }
+        return String.join(";", stringValues);
+    }
 }

flink-kubernetes-operator-api/src/test/java/org/apache/flink/kubernetes/operator/api/spec/ConfigObjectNodeTest.java

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.flink.kubernetes.operator.api.spec;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ConfigObjectNodeTest {
+
+    private final ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
+
+    @BeforeEach
+    void setup() {
+        SimpleModule module = new SimpleModule();
+        module.addDeserializer(ConfigObjectNode.class, new ConfigObjectNodeDeserializer());
+        objectMapper.registerModule(module);
+    }
+
+    @Test
+    void deserializeArray() throws JsonProcessingException {
+        var value = "a: 1\n" + "b:\n" + " c: [1,2]";
+
+        var flatMap = objectMapper.readValue(value, ConfigObjectNode.class).asFlatMap();
+
+        assertThat(flatMap).containsExactlyInAnyOrderEntriesOf(Map.of("a", "1", "b.c", "1;2"));
+    }
+
+    @Test
+    void deserializeStringArray() throws JsonProcessingException {
+        var value = "a: 1\n" + "b:\n" + " c: [\"1\",\"2\"]";
+
+        var flatMap = objectMapper.readValue(value, ConfigObjectNode.class).asFlatMap();
+
+        assertThat(flatMap).containsExactlyInAnyOrderEntriesOf(Map.of("a", "1", "b.c", "1;2"));
+    }
+}