fix: refactor compute and cloudshell credentials to pass quota project to base class (#1284)

* fix:refactor compute and cloudshell credentials to pass quota project to base class

* rebase

* remove protected

* remove empty line

* Add tests

* format fix

Author: sai-sunder-s

oauth2_http/java/com/google/auth/oauth2/CloudShellCredentials.java

@@ -67,8 +67,9 @@ public static CloudShellCredentials create(int authPort) {
     return CloudShellCredentials.newBuilder().setAuthPort(authPort).build();
   }
 
-  private CloudShellCredentials(int authPort) {
-    this.authPort = authPort;
+  private CloudShellCredentials(Builder builder) {
+    super(builder);
+    this.authPort = builder.getAuthPort();
   }
 
   protected int getAuthPort() {
@@ -139,13 +140,19 @@ public Builder setAuthPort(int authPort) {
       return this;
     }
 
+    @CanIgnoreReturnValue
+    public Builder setQuotaProjectId(String quotaProjectId) {
+      super.quotaProjectId = quotaProjectId;
+      return this;
+    }
+
     public int getAuthPort() {
       return authPort;
     }
 
     @Override
     public CloudShellCredentials build() {
-      return new CloudShellCredentials(authPort);
+      return new CloudShellCredentials(this);
     }
   }
 }

oauth2_http/javatests/com/google/auth/oauth2/CloudShellCredentialsTest.java

@@ -124,4 +124,20 @@ public void serialize() throws IOException, ClassNotFoundException {
     assertEquals(credentials.toString(), deserializedCredentials.toString());
     assertSame(deserializedCredentials.clock, Clock.SYSTEM);
   }
+
+  @Test
+  public void toBuilder() {
+    CloudShellCredentials credentials =
+        CloudShellCredentials.newBuilder()
+            .setAuthPort(42)
+            .setQuotaProjectId("quota-project")
+            .build();
+
+    assertEquals(42, credentials.getAuthPort());
+    assertEquals("quota-project", credentials.getQuotaProjectId());
+
+    CloudShellCredentials secondCredentials = credentials.toBuilder().build();
+
+    assertEquals(credentials, secondCredentials);
+  }
 }

oauth2_http/javatests/com/google/auth/oauth2/DefaultCredentialsProviderTest.java

@@ -460,6 +460,34 @@ public void getDefaultCredentials_quota_project() throws IOException {
     testUserProvidesToken(testProvider, USER_CLIENT_ID, USER_CLIENT_SECRET, REFRESH_TOKEN);
   }
 
+  @Test
+  public void getDefaultCredentials_compute_quotaProject() throws IOException {
+    MockMetadataServerTransportFactory transportFactory = new MockMetadataServerTransportFactory();
+    transportFactory.transport.setAccessToken(ACCESS_TOKEN);
+    TestDefaultCredentialsProvider testProvider = new TestDefaultCredentialsProvider();
+    testProvider.setEnv(
+        DefaultCredentialsProvider.QUOTA_PROJECT_ENV_VAR, QUOTA_PROJECT_FROM_ENVIRONMENT);
+
+    GoogleCredentials defaultCredentials = testProvider.getDefaultCredentials(transportFactory);
+
+    assertTrue(defaultCredentials instanceof ComputeEngineCredentials);
+    assertEquals(QUOTA_PROJECT_FROM_ENVIRONMENT, defaultCredentials.getQuotaProjectId());
+  }
+
+  @Test
+  public void getDefaultCredentials_cloudshell_quotaProject() throws IOException {
+    MockHttpTransportFactory transportFactory = new MockHttpTransportFactory();
+    TestDefaultCredentialsProvider testProvider = new TestDefaultCredentialsProvider();
+    testProvider.setEnv(DefaultCredentialsProvider.CLOUD_SHELL_ENV_VAR, "4");
+    testProvider.setEnv(
+        DefaultCredentialsProvider.QUOTA_PROJECT_ENV_VAR, QUOTA_PROJECT_FROM_ENVIRONMENT);
+
+    GoogleCredentials defaultCredentials = testProvider.getDefaultCredentials(transportFactory);
+
+    assertTrue(defaultCredentials instanceof CloudShellCredentials);
+    assertEquals(QUOTA_PROJECT_FROM_ENVIRONMENT, defaultCredentials.getQuotaProjectId());
+  }
+
   @Test
   public void getDefaultCredentials_envNoGceCheck_noGceRequest() throws IOException {
     MockRequestCountingTransportFactory transportFactory =