Validate condition router YAML before parsing

dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/router/condition/config/model/ConditionRuleParser.java

@@ -49,10 +49,15 @@ public class ConditionRuleParser {
 
     private static final ErrorTypeAwareLogger logger = LoggerFactory.getErrorTypeAwareLogger(ConditionRuleParser.class);
 
+    @SuppressWarnings("unchecked")
     public static AbstractRouterRule parse(String rawRule) {
         AbstractRouterRule rule;
         Yaml yaml = new Yaml(new SafeConstructor(new LoaderOptions()));
-        Map<String, Object> map = yaml.load(rawRule);
+        Object parsedRule = yaml.load(rawRule);
+        if (!(parsedRule instanceof Map)) {
+            throw new IllegalArgumentException("Condition router rule must be a YAML mapping.");
+        }
+        Map<String, Object> map = (Map<String, Object>) parsedRule;
         String confVersion = (String) map.get(CONFIG_VERSION_KEY);
 
         if (confVersion != null && confVersion.toLowerCase().startsWith(RULE_VERSION_V31)) {

dubbo-cluster/src/test/java/org/apache/dubbo/rpc/cluster/router/condition/config/ConditionRuleParserTest.java

@@ -0,0 +1,63 @@
+/*
+ * 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.dubbo.rpc.cluster.router.condition.config;
+
+import org.apache.dubbo.common.URL;
+import org.apache.dubbo.common.config.configcenter.ConfigChangeType;
+import org.apache.dubbo.common.config.configcenter.ConfigChangedEvent;
+import org.apache.dubbo.rpc.cluster.router.condition.config.model.ConditionRuleParser;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ConditionRuleParserTest {
+
+    @Test
+    public void testRejectNonMappingRule() {
+        for (String rawRule : Arrays.asList("", " ", "# comment", "---", "null", "[]", "condition")) {
+            IllegalArgumentException exception =
+                    Assertions.assertThrows(IllegalArgumentException.class, () -> ConditionRuleParser.parse(rawRule));
+            Assertions.assertEquals("Condition router rule must be a YAML mapping.", exception.getMessage());
+        }
+    }
+
+    @Test
+    public void testCommentOnlyRuleUpdatePreservesPreviousRule() {
+        String rawRule = "configVersion: v3.1\n" + "scope: service\n"
+                + "key: com.foo.BarService\n"
+                + "force: true\n"
+                + "runtime: true\n"
+                + "enabled: true\n"
+                + "conditions:\n"
+                + "  - from:\n"
+                + "      match: env=gray\n"
+                + "    to:\n"
+                + "      - match: env!=gray\n"
+                + "        weight: 100";
+
+        ServiceStateRouter<String> router = new ServiceStateRouter<>(
+                URL.valueOf("consumer://127.0.0.1/com.foo.BarService?env=gray&region=beijing"));
+        router.process(new ConfigChangedEvent("com.foo.BarService", "", rawRule, ConfigChangeType.ADDED));
+        Assertions.assertTrue(router.isForce());
+
+        router.process(new ConfigChangedEvent("com.foo.BarService", "", "# comment", ConfigChangeType.MODIFIED));
+
+        Assertions.assertTrue(router.isForce());
+    }
+}