Merge pull request #1983 from cbuschka/issue1802_npex_when_server_not_set

#1802 Check if server is available from kubeconfig.

Author: k8s-ci-robot

util/src/main/java/io/kubernetes/client/util/ClientBuilder.java

@@ -277,6 +277,9 @@ public static ClientBuilder kubeconfig(KubeConfig config) throws IOException {
     final ClientBuilder builder = new ClientBuilder();
 
     String server = config.getServer();
+    if (server == null) {
+      throw new IllegalArgumentException("No server in kubeconfig");
+    }
     if (!server.contains("://")) {
       if (server.contains(":443")) {
         server = "https://" + server;

util/src/test/java/io/kubernetes/client/util/ClientBuilderTest.java

@@ -18,6 +18,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
@@ -299,4 +300,16 @@ public void testSettingPassphraseForKubeConfigShouldWork() throws IOException {
         ((ClientCertificateAuthentication) receivingAuthn.getDelegateAuthentication())
             .getPassphrase());
   }
+
+  @Test
+  public void testDetectsServerNotSet() {
+    assertThrows(
+        "No server in kubeconfig",
+        IllegalArgumentException.class,
+        () -> {
+          KubeConfig kubeConfigWithoutServer = mock(KubeConfig.class);
+
+          ClientBuilder.kubeconfig(kubeConfigWithoutServer);
+        });
+  }
 }