chore: enable lint presubmit and run code formatter (#312)

* Add lint test and com.coveo:fmt-maven-plugin configuration

* Run the formatter

Author: chingor13

google-auth-library-java/.kokoro/build.sh

@@ -22,6 +22,21 @@ java -version
 echo $JOB_TYPE
 
 mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
-mvn test -B
 
-bash $KOKORO_GFILE_DIR/codecov.sh
+case ${JOB_TYPE} in
+test)
+    mvn test -B
+    bash ${KOKORO_GFILE_DIR}/codecov.sh
+    ;;
+lint)
+    mvn com.coveo:fmt-maven-plugin:check
+    ;;
+javadoc)
+    mvn javadoc:javadoc javadoc:test-javadoc
+    ;;
+integration)
+    mvn -B -pl ${INTEGRATION_TEST_ARGS} -DtrimStackTrace=false -fae verify
+    ;;
+*)
+    ;;
+esac

google-auth-library-java/.kokoro/continuous/lint.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+
+env_vars: {
+    key: "TRAMPOLINE_IMAGE"
+    value: "gcr.io/cloud-devrel-kokoro-resources/java8"
+}
+
+env_vars: {
+    key: "JOB_TYPE"
+    value: "lint"
+}

google-auth-library-java/.kokoro/presubmit/lint.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+
+env_vars: {
+    key: "TRAMPOLINE_IMAGE"
+    value: "gcr.io/cloud-devrel-kokoro-resources/java8"
+}
+
+env_vars: {
+    key: "JOB_TYPE"
+    value: "lint"
+}

google-auth-library-java/appengine/java/com/google/auth/appengine/AppEngineCredentials.java

@@ -41,7 +41,6 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
-
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.util.Collection;
@@ -58,9 +57,10 @@
 public class AppEngineCredentials extends GoogleCredentials implements ServiceAccountSigner {
 
   private static final Logger LOGGER = Logger.getLogger(AppEngineCredentials.class.getName());
-  private static final String APPLICATION_DEFAULT_CREDENTIALS_WARNING = "You are attempting to "
-      + "fetch Application Default Credentials from com.google.auth.appengine.AppEngineCredentials."
-      + " This method will not return a com.google.auth.appengine.AppEngineCredentials instance.";
+  private static final String APPLICATION_DEFAULT_CREDENTIALS_WARNING =
+      "You are attempting to "
+          + "fetch Application Default Credentials from com.google.auth.appengine.AppEngineCredentials."
+          + " This method will not return a com.google.auth.appengine.AppEngineCredentials instance.";
   private static final long serialVersionUID = -2627708355455064660L;
 
   private final String appIdentityServiceClassName;
@@ -71,8 +71,9 @@ public class AppEngineCredentials extends GoogleCredentials implements ServiceAc
 
   /**
    * {@inheritDoc}
+   *
    * @deprecated AppEngineCredentials should be instantiated via its Builder. See
-   * https://github.com/googleapis/google-auth-library-java#google-auth-library-appengine
+   *     https://github.com/googleapis/google-auth-library-java#google-auth-library-appengine
    */
   @Deprecated
   public static GoogleCredentials getApplicationDefault() throws IOException {
@@ -82,8 +83,9 @@ public static GoogleCredentials getApplicationDefault() throws IOException {
 
   /**
    * {@inheritDoc}
+   *
    * @deprecated AppEngineCredentials should be instantiated via its Builder. See
-   * https://github.com/googleapis/google-auth-library-java#google-auth-library-appengine
+   *     https://github.com/googleapis/google-auth-library-java#google-auth-library-appengine
    */
   @Deprecated
   public static GoogleCredentials getApplicationDefault(HttpTransportFactory transportFactory)
@@ -94,15 +96,15 @@ public static GoogleCredentials getApplicationDefault(HttpTransportFactory trans
 
   private AppEngineCredentials(Collection<String> scopes, AppIdentityService appIdentityService) {
     this.scopes = scopes == null ? ImmutableSet.<String>of() : ImmutableList.copyOf(scopes);
-    this.appIdentityService = appIdentityService != null ? appIdentityService 
-        : AppIdentityServiceFactory.getAppIdentityService();
+    this.appIdentityService =
+        appIdentityService != null
+            ? appIdentityService
+            : AppIdentityServiceFactory.getAppIdentityService();
     this.appIdentityServiceClassName = this.appIdentityService.getClass().getName();
     scopesRequired = this.scopes.isEmpty();
   }
 
-  /**
-   * Refresh the access token by getting it from the App Identity service
-   */
+  /** Refresh the access token by getting it from the App Identity service */
   @Override
   public AccessToken refreshAccessToken() throws IOException {
     if (createScopedRequired()) {
@@ -113,7 +115,7 @@ public AccessToken refreshAccessToken() throws IOException {
     Date expirationTime = accessTokenResponse.getExpirationTime();
     return new AccessToken(accessToken, expirationTime);
   }
-  
+
   @Override
   public boolean createScopedRequired() {
     return scopesRequired;