SOLR-18318: Fix NPE in GetNodeSystemInfo when nodes param is set

changelog/unreleased/Yashgoswami-SOLR-18318.yml

@@ -0,0 +1,10 @@
+# See https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc
+
+title: >
+  Fix NullPointerException in GetNodeSystemInfo when the nodes parameter is provided in SolrCloud mode
+type: fixed
+authors:
+  - name: Yash Goswami
+links:
+  - name: SOLR-18318
+    url: https://issues.apache.org/jira/browse/SOLR-18318

solr/api/src/java/org/apache/solr/client/api/model/NodeSystemResponse.java

@@ -23,13 +23,13 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.LinkedHashMap;
 
 /** Response from /node/system */
 public class NodeSystemResponse extends SolrJerseyResponse {
 
-  // TODO The typing here is kindof wonky - can I tighten 'Object' here to be NodeSystemResponse or
-  // will Jackson choke on that?
-  public Map<String, Object> remoteNodeData;
+  // Object, not NodeSystemResponse, since @JsonAnySetter below also feeds this map raw values.
+  public Map<String, Object> remoteNodeData = new LinkedHashMap<>();
 
   @JsonAnyGetter
   public Map<String, Object> remoteNodeData() {

solr/core/src/test/org/apache/solr/handler/admin/api/GetNodeSystemInfoSolrCloudTest.java

@@ -0,0 +1,32 @@
+package org.apache.solr.handler.admin.api;
+
+import org.apache.solr.client.solrj.request.CollectionAdminRequest;
+import org.apache.solr.client.solrj.request.SystemApi;
+import org.apache.solr.cloud.SolrCloudTestCase;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class GetNodeSystemInfoSolrCloudTest extends SolrCloudTestCase {
+
+  @BeforeClass
+  public static void setupCluster() throws Exception {
+    configureCluster(1).addConfig("conf", configset("cloud-minimal")).configure();
+    CollectionAdminRequest.createCollection(DEFAULT_TEST_COLLECTION_NAME, "conf", 1, 1)
+        .process(cluster.getSolrClient());
+  }
+
+  @Test
+  public void testGetNodeInfoWithNodesParam() throws Exception {
+    String nodeName =
+        cluster.getJettySolrRunners().get(0).getCoreContainer().getZkController().getNodeName();
+
+    final var req = new SystemApi.GetNodeSystemInfo();
+    req.setNodes(nodeName);
+
+    final var infoRsp = req.process(cluster.getSolrClient());
+
+    assertEquals(0, infoRsp.responseHeader.status);
+    assertNotNull(infoRsp.remoteNodeData);
+    assertTrue(infoRsp.remoteNodeData.containsKey(nodeName));
+  }
+}