Assert NodeClient in client wrapper (#113515) (#113521)

Some `getClientWrapper()` implementations return a wrapper that only
wraps `NodeClient` instances. In practice we _only_ wrap `NodeClient`
instances so this check is redundant, and in a recent investigation it
was confusing to readers. With this commit we assert that we're always
wrapping a `NodeClient`.

Author: DaveCTurner

x-pack/plugin/identity-provider/src/internalClusterTest/java/org/elasticsearch/xpack/idp/saml/test/IdentityProviderIntegTestCase.java

@@ -158,7 +158,7 @@ protected Function<Client, Client> getClientWrapper() {
         // user. This is ok for internal n2n stuff but the test framework does other things like wiping indices, repositories, etc
         // that the system user cannot do. so we wrap the node client with a user that can do these things since the client() calls
         // return a node client
-        return client -> (client instanceof NodeClient) ? client.filterWithHeader(headers) : client;
+        return client -> asInstanceOf(NodeClient.class, client).filterWithHeader(headers);
     }
 
     @Override

x-pack/plugin/ml/qa/native-multi-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/ml/integration/MlNativeIntegTestCase.java

@@ -18,6 +18,7 @@
 import org.elasticsearch.action.support.broadcast.BroadcastResponse;
 import org.elasticsearch.action.support.master.AcknowledgedResponse;
 import org.elasticsearch.client.internal.Client;
+import org.elasticsearch.client.internal.node.NodeClient;
 import org.elasticsearch.cluster.ClusterModule;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.NamedDiff;
@@ -172,7 +173,7 @@ protected Function<Client, Client> getClientWrapper() {
         // user. This is ok for internal n2n stuff but the test framework does other things like wiping indices, repositories, etc
         // that the system user cannot do. so we wrap the node client with a user that can do these things since the client() calls
         // return a node client
-        return client -> client.filterWithHeader(headers);
+        return client -> asInstanceOf(NodeClient.class, client).filterWithHeader(headers);
     }
 
     private Settings externalClusterClientSettings() {

x-pack/plugin/security/src/test/java/org/elasticsearch/test/SecurityIntegTestCase.java

@@ -379,7 +379,7 @@ protected Function<Client, Client> getClientWrapper() {
         // user. This is ok for internal n2n stuff but the test framework does other things like wiping indices, repositories, etc
         // that the system user cannot do. so we wrap the node client with a user that can do these things since the client() calls
         // return a node client
-        return client -> (client instanceof NodeClient) ? client.filterWithHeader(headers) : client;
+        return client -> asInstanceOf(NodeClient.class, client).filterWithHeader(headers);
     }
 
     /**