SOLR-18103: Remove deprecated solr.xml <metrics><hiddenSysProps></metrics> (#4136)

Author: epugh

changelog/unreleased/SOLR-18103.yml

@@ -0,0 +1,8 @@
+# See https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc
+title: Remove deprecated hiddenSysProps setting under "metrics" in solr.xml.  It remains a standard top level config setting.
+type: removed # added, changed, fixed, deprecated, removed, dependency_update, security, other
+authors:
+  - name: Eric Pugh
+links:
+  - name: SOLR-18103
+    url: https://issues.apache.org/jira/browse/SOLR-18103

solr/core/src/java/org/apache/solr/core/SolrXmlConfig.java

@@ -165,10 +165,6 @@ public static NodeConfig fromConfig(
     configBuilder.setBackupRepositoryPlugins(
         getBackupRepositoryPluginInfos(root.get("backup").getAll("repository")));
     configBuilder.setClusterPlugins(getClusterPlugins(loader, root));
-    // <metrics><hiddenSysProps></metrics> will be removed in Solr 10, but until then, use it if a
-    // <hiddenSysProps> is not provided under <solr>.
-    // Remove this line in 10.0
-    configBuilder.setHiddenSysProps(getHiddenSysProps(root.get("metrics")));
     configBuilder.setMetricsConfig(getMetricsConfig(root.get("metrics")));
     configBuilder.setCachesConfig(getCachesConfig(loader, root.get("caches")));
     configBuilder.setDefaultZkHost(defaultZkHost);
@@ -747,26 +743,6 @@ private static Object decodeNullValue(Object o) {
     return o;
   }
 
-  /**
-   * Deprecated as of 9.3, will be removed in 10.0
-   *
-   * @param metrics configNode for the metrics
-   * @return a comma-separated list of hidden Sys Props
-   */
-  @Deprecated(forRemoval = true, since = "9.3")
-  private static String getHiddenSysProps(ConfigNode metrics) {
-    ConfigNode p = metrics.get("hiddenSysProps");
-    if (!p.exists()) return null;
-    Set<String> props = new HashSet<>();
-    p.forEachChild(
-        it -> {
-          if (it.name().equals("str") && StrUtils.isNotNullOrEmpty(it.txt()))
-            props.add(Pattern.quote(it.txt()));
-          return Boolean.TRUE;
-        });
-    return String.join(",", props);
-  }
-
   private static PluginInfo getPluginInfo(ConfigNode cfg) {
     if (cfg == null || !cfg.exists()) return null;
     final var pluginInfo = new PluginInfo(cfg, cfg.name(), false, true);