Revert "fix(auth): Address ClientSideCredentialAccessBoundary RefreshTask rac…"

This reverts commit 30088d2.

Author: lqiu96

google-auth-library-java/cab-token-generator/java/com/google/auth/credentialaccessboundary/ClientSideCredentialAccessBoundaryFactory.java

@@ -53,6 +53,7 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Strings;
 import com.google.common.util.concurrent.AbstractFuture;
+import com.google.common.util.concurrent.FutureCallback;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListenableFutureTask;
@@ -78,6 +79,7 @@
 import java.util.Date;
 import java.util.List;
 import java.util.concurrent.ExecutionException;
+import javax.annotation.Nullable;
 
 /**
  * A factory for generating downscoped access tokens using a client-side approach.
@@ -246,7 +248,7 @@ void refreshCredentialsIfRequired() throws IOException {
         }
         try {
           // Wait for the refresh task to complete.
-          currentRefreshTask.get();
+          currentRefreshTask.task.get();
         } catch (InterruptedException e) {
           // Restore the interrupted status and throw an exception.
           Thread.currentThread().interrupt();
@@ -493,18 +495,31 @@ class RefreshTask extends AbstractFuture<IntermediateCredentials> implements Run
       this.task = task;
       this.isNew = isNew;
 
-      // Single listener to guarantee that finishRefreshTask updates the internal state BEFORE
-      // the outer future completes and unblocks waiters.
+      // Add listener to update factory's credentials when the task completes.
       task.addListener(
           () -> {
             try {
               finishRefreshTask(task);
-              RefreshTask.this.set(Futures.getDone(task));
             } catch (ExecutionException e) {
               Throwable cause = e.getCause();
-              RefreshTask.this.setException(cause != null ? cause : e);
-            } catch (Throwable t) {
-              RefreshTask.this.setException(t);
+              RefreshTask.this.setException(cause);
+            }
+          },
+          MoreExecutors.directExecutor());
+
+      // Add callback to set the result or exception based on the outcome.
+      Futures.addCallback(
+          task,
+          new FutureCallback<IntermediateCredentials>() {
+            @Override
+            public void onSuccess(IntermediateCredentials result) {
+              RefreshTask.this.set(result);
+            }
+
+            @Override
+            public void onFailure(@Nullable Throwable t) {
+              RefreshTask.this.setException(
+                  t != null ? t : new IOException("Refresh failed with null Throwable."));
             }
           },
           MoreExecutors.directExecutor());

google-auth-library-java/cab-token-generator/javatests/com/google/auth/credentialaccessboundary/ClientSideCredentialAccessBoundaryFactoryTest.java

@@ -988,59 +988,4 @@ void generateToken_withMalformSessionKey_failure() throws Exception {
 
     assertThrows(GeneralSecurityException.class, () -> factory.generateToken(accessBoundary));
   }
-
-  @Test
-  void generateToken_freshInstance_concurrent_noNpe() throws Exception {
-    for (int run = 0; run < 10; run++) { // Run 10 times in a single test instance to save time
-      GoogleCredentials sourceCredentials =
-          getServiceAccountSourceCredentials(mockTokenServerTransportFactory);
-      ClientSideCredentialAccessBoundaryFactory factory =
-          ClientSideCredentialAccessBoundaryFactory.newBuilder()
-              .setSourceCredential(sourceCredentials)
-              .setHttpTransportFactory(mockStsTransportFactory)
-              .build();
-
-      CredentialAccessBoundary.Builder cabBuilder = CredentialAccessBoundary.newBuilder();
-      CredentialAccessBoundary accessBoundary =
-          cabBuilder
-              .addRule(
-                  CredentialAccessBoundary.AccessBoundaryRule.newBuilder()
-                      .setAvailableResource("resource")
-                      .setAvailablePermissions(ImmutableList.of("role"))
-                      .build())
-              .build();
-
-      int numThreads = 5;
-      CountDownLatch latch = new CountDownLatch(numThreads);
-      java.util.concurrent.atomic.AtomicInteger npeCount =
-          new java.util.concurrent.atomic.AtomicInteger();
-      java.util.concurrent.ExecutorService executor =
-          java.util.concurrent.Executors.newFixedThreadPool(numThreads);
-
-      try {
-        for (int i = 0; i < numThreads; i++) {
-          executor.submit(
-              () -> {
-                try {
-                  latch.countDown();
-                  latch.await();
-                  factory.generateToken(accessBoundary);
-                } catch (NullPointerException e) {
-                  npeCount.incrementAndGet();
-                } catch (Exception e) {
-                  // Ignore other exceptions for the sake of the race reproduction
-                }
-              });
-        }
-      } finally {
-        executor.shutdown();
-        executor.awaitTermination(5, java.util.concurrent.TimeUnit.SECONDS);
-      }
-
-      org.junit.jupiter.api.Assertions.assertEquals(
-          0,
-          npeCount.get(),
-          "Expected zero NullPointerExceptions due to the race condition, but some were thrown.");
-    }
-  }
 }