Update x-goog-api-client header to use gl-java and gdcl tokens (#1354)

* Update x-goog-api-client header to use gl-java and gdcl tokens

* Refactor to use constant.

We no longer need to inspect which service client is being used at
runtime so switch to using a constant.

google-api-client/src/main/java/com/google/api/client/googleapis/services/AbstractGoogleClientRequest.java

@@ -131,47 +131,39 @@ protected AbstractGoogleClientRequest(AbstractGoogleClient abstractGoogleClient,
       requestHeaders.setUserAgent(USER_AGENT_SUFFIX);
     }
     // Set the header for the Api Client version (Java and OS version)
-    requestHeaders.set(
-      API_VERSION_HEADER,
-      ApiClientVersion.getDefault().build(abstractGoogleClient.getClass().getSimpleName())
-    );
+    requestHeaders.set(API_VERSION_HEADER, ApiClientVersion.DEFAULT_VERSION);
   }
 
   /**
-   * Internal class to help build the X-Goog-Api-Client header. This header identifies the
-   * API Client version and environment.
-   *
-   * See <a href="https://cloud.google.com/apis/docs/system-parameters"></a>
+   * Internal class to help build the X-Goog-Api-Client header. This header identifies the API
+   * Client version and environment.
    *
+   * <p>See <a href="https://cloud.google.com/apis/docs/system-parameters"></a>
    */
   static class ApiClientVersion {
-    private static final ApiClientVersion DEFAULT_VERSION = new ApiClientVersion();
-    private final String headerTemplate;
+    static final String DEFAULT_VERSION = new ApiClientVersion().toString();
+    private final String versionString;
 
     ApiClientVersion() {
       this(getJavaVersion(), OS_NAME.value(), OS_VERSION.value(), GoogleUtils.VERSION);
     }
 
     ApiClientVersion(String javaVersion, String osName, String osVersion, String clientVersion) {
-      StringBuilder sb = new StringBuilder("java/");
+      StringBuilder sb = new StringBuilder("gl-java/");
       sb.append(formatSemver(javaVersion));
-      sb.append(" http-google-%s/");
+      sb.append(" gdcl/");
       sb.append(formatSemver(clientVersion));
       if (osName != null && osVersion != null) {
         sb.append(" ");
         sb.append(formatName(osName));
         sb.append("/");
         sb.append(formatSemver(osVersion));
       }
-      this.headerTemplate = sb.toString();
-    }
-
-    String build(String clientName) {
-      return String.format(headerTemplate, formatName(clientName));
+      this.versionString = sb.toString();
     }
 
-    private static ApiClientVersion getDefault() {
-      return DEFAULT_VERSION;
+    public String toString() {
+      return versionString;
     }
 
     private static String getJavaVersion() {

google-api-client/src/test/java/com/google/api/client/googleapis/services/AbstractGoogleClientRequestTest.java

@@ -214,43 +214,52 @@ public void testUserAgentSuffix() throws Exception {
     request.executeUnparsed();
   }
 
-  public void testUserAgent() throws Exception {
+  public void testUserAgent() throws IOException {
     AssertUserAgentTransport transport = new AssertUserAgentTransport();
     transport.expectedUserAgent = AbstractGoogleClientRequest.USER_AGENT_SUFFIX + " " + HttpRequest.USER_AGENT_SUFFIX;
     // Don't specify an Application Name.
     MockGoogleClient client = new MockGoogleClient.Builder(
         transport, ROOT_URL, SERVICE_PATH, JSON_OBJECT_PARSER, null).build();
     MockGoogleClientRequest<Void> request =
-        new MockGoogleClientRequest<Void>(client, HttpMethods.GET, URI_TEMPLATE, null, Void.class);
+        new MockGoogleClientRequest<>(client, HttpMethods.GET, URI_TEMPLATE, null, Void.class);
     request.executeUnparsed();
   }
 
-  public void testSetsApiClientHeader() throws Exception {
-    HttpTransport transport = new AssertHeaderTransport("X-Goog-Api-Client", "java/\\d+\\.\\d+\\.\\d+.*");
+  public void testSetsApiClientHeader() throws IOException {
+    HttpTransport transport = new AssertHeaderTransport("X-Goog-Api-Client", "gl-java/\\d+\\.\\d+\\.\\d+.*");
     MockGoogleClient client = new MockGoogleClient.Builder(
         transport, ROOT_URL, SERVICE_PATH, JSON_OBJECT_PARSER, null).build();
     MockGoogleClientRequest<Void> request =
-        new MockGoogleClientRequest<Void>(client, HttpMethods.GET, URI_TEMPLATE, null, Void.class);
+        new MockGoogleClientRequest<>(client, HttpMethods.GET, URI_TEMPLATE, null, Void.class);
     request.executeUnparsed();
   }
 
-  public void testSetsApiClientHeaderWithOsVersion() throws Exception {
+  public void testSetsApiClientHeaderWithOsVersion() {
     System.setProperty("os.name", "My OS");
     System.setProperty("os.version", "1.2.3");
 
-    String version = new ApiClientVersion().build("My Client");
+    String version = new ApiClientVersion().toString();
     assertTrue("Api version should contain the os version", version.matches(".* my-os/1.2.3"));
   }
 
-  public void testSetsApiClientHeaderWithoutOsVersion() throws Exception {
+  public void testSetsApiClientHeaderWithoutOsVersion() {
     System.setProperty("os.name", "My OS");
     System.clearProperty("os.version");
     assertNull(System.getProperty("os.version"));
 
-    String version = new ApiClientVersion().build("My Client");
+    String version = new ApiClientVersion().toString();
     assertFalse("Api version should not contain the os version", version.matches(".*my-os.*"));
   }
 
+  public void testSetsApiClientHeaderDiscoveryVersion() throws IOException {
+    HttpTransport transport = new AssertHeaderTransport("X-Goog-Api-Client", ".*gdcl/\\d+\\.\\d+\\.\\d+.*");
+    MockGoogleClient client = new MockGoogleClient.Builder(
+            transport, ROOT_URL, SERVICE_PATH, JSON_OBJECT_PARSER, null).build();
+    MockGoogleClientRequest<Void> request =
+            new MockGoogleClientRequest<>(client, HttpMethods.GET, URI_TEMPLATE, null, Void.class);
+    request.executeUnparsed();
+  }
+
   public void testReturnRawInputStream_defaultFalse() throws Exception {
     HttpTransport transport = new MockHttpTransport() {
       @Override