We pass `null` for the class name here:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L261

However the class name is mandatory for the transport protocol today:

https://github.com/elastic/elasticsearch/blob/f086dd18ddc705bf84a1ff99d35196ec2498fd52/server/src/main/java/org/elasticsearch/plugins/PluginDescriptor.java#L156

This prevents various APIs from working in a cluster with stable plugins installed.
server/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
Files.copy(jar, fake1.resolve("plugin.jar"));
        }
        PluginTestUtil.writePluginProperties(
            fake2,
            "description",
            "description",
            "name",
            "fake",
            "version",
            "1.0.0",
            "elasticsearch.version",
            Version.CURRENT.toString(),
            "java.version",
            System.getProperty("java.specification.version"),
            "classname",
            "test.NonExtensiblePlugin"
        );
        try (InputStream jar = PluginsServiceTests.class.getResourceAsStream("non-extensible-plugin.jar")) {
            Files.copy(jar, fake2.resolve("plugin.jar"));
        }
        final Settings settings = Settings.builder().put("path.home", pathHome).build();
        IllegalStateException e = expectThrows(IllegalStateException.class, () -> newPluginsService(settings));
        assertThat(e.getMessage(), containsString("duplicate plugin: "));
        assertThat(e.getMessage(), containsString("Name: fake"));
    }
    public void testExistingMandatoryInstalledPlugin() throws IOException {
        final Path pathHome = createTempDir(getTestName());
        final Path plugins = pathHome.resolve("plugins");
        final Path fake = plugins.resolve("fake");
        PluginTestUtil.writePluginProperties(