auth: handle null value from getRequestMetadata().

It appears some Credentials implementations may return null.

2 files changed, 37 insertions, 2 deletions

diff --git a/auth/src/main/java/io/grpc/auth/GoogleAuthLibraryCallCredentials.java b/auth/src/main/java/io/grpc/auth/GoogleAuthLibraryCallCredentials.java
index e5b5cd731..85ab1b581 100644
--- a/auth/src/main/java/io/grpc/auth/GoogleAuthLibraryCallCredentials.java
+++ b/auth/src/main/java/io/grpc/auth/GoogleAuthLibraryCallCredentials.java
@@ -50,6 +50,7 @@ import java.net.URISyntaxException;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
+import javax.annotation.Nullable;
 
 /**
  * Wraps {@link Credentials} as a {@link CallCredentials}.
@@ -84,17 +85,20 @@ final class GoogleAuthLibraryCallCredentials implements CallCredentials {
           try {
             // Credentials is expected to manage caching internally if the metadata is fetched over
             // the network.
+            //
             // TODO(zhangkun83): we don't know whether there is valid cache data. If there is, we
             // would waste a context switch by always scheduling in executor. However, we have to
             // do so because we can't risk blocking the network thread. This can be resolved after
             // https://github.com/google/google-auth-library-java/issues/3 is resolved.
+            //
+            // Some implementations may return null here.
             Map<String, List<String>> metadata = creds.getRequestMetadata(uri);
             // Re-use the headers if getRequestMetadata() returns the same map. It may return a
             // different map based on the provided URI, i.e., for JWT. However, today it does not
             // cache JWT and so we won't bother tring to save its return value based on the URI.
             Metadata headers;
             synchronized (GoogleAuthLibraryCallCredentials.this) {
-              if (lastMetadata != metadata) {
+              if (lastMetadata == null || lastMetadata != metadata) {
                 lastMetadata = metadata;
                 lastHeaders = toHeaders(metadata);
               }
@@ -146,7 +150,7 @@ final class GoogleAuthLibraryCallCredentials implements CallCredentials {
     }
   }
 
-  private static Metadata toHeaders(Map<String, List<String>> metadata) {
+  private static Metadata toHeaders(@Nullable Map<String, List<String>> metadata) {
     Metadata headers = new Metadata();
     if (metadata != null) {
       for (String key : metadata.keySet()) {
diff --git a/auth/src/test/java/io/grpc/auth/GoogleAuthLibraryCallCredentialsTests.java b/auth/src/test/java/io/grpc/auth/GoogleAuthLibraryCallCredentialsTests.java
index d99812f3d..c993625e4 100644
--- a/auth/src/test/java/io/grpc/auth/GoogleAuthLibraryCallCredentialsTests.java
+++ b/auth/src/test/java/io/grpc/auth/GoogleAuthLibraryCallCredentialsTests.java
@@ -37,6 +37,7 @@ import static org.junit.Assert.assertEquals;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -71,6 +72,7 @@ import java.io.IOException;
 import java.net.URI;
 import java.util.ArrayList;
 import java.util.Date;
+import java.util.List;
 import java.util.concurrent.Executor;
 
 /**
@@ -194,6 +196,35 @@ public class GoogleAuthLibraryCallCredentialsTests {
   }
 
   @Test
+  @SuppressWarnings("unchecked")
+  public void credentialsReturnNullMetadata() throws Exception {
+    ListMultimap<String, String> values = LinkedListMultimap.create();
+    values.put("Authorization", "token1");
+    when(credentials.getRequestMetadata(eq(expectedUri)))
+        .thenReturn(null, Multimaps.<String, String>asMap(values), null);
+
+    GoogleAuthLibraryCallCredentials callCredentials =
+        new GoogleAuthLibraryCallCredentials(credentials);
+    for (int i = 0; i < 3; i++) {
+      callCredentials.applyRequestMetadata(method, attrs, executor, applier);
+    }
+
+    assertEquals(3, runPendingRunnables());
+    verify(credentials, times(3)).getRequestMetadata(eq(expectedUri));
+
+    verify(applier, times(3)).apply(headersCaptor.capture());
+    List<Metadata> headerList = headersCaptor.getAllValues();
+    assertEquals(3, headerList.size());
+
+    assertEquals(0, headerList.get(0).headerCount());
+
+    Iterable<String> authorization = headerList.get(1).getAll(AUTHORIZATION);
+    assertArrayEquals(new String[]{"token1"}, Iterables.toArray(authorization, String.class));
+
+    assertEquals(0, headerList.get(2).headerCount());
+  }
+
+  @Test
   public void oauth2Credential() {
     final AccessToken token = new AccessToken("allyourbase", new Date(Long.MAX_VALUE));
     final OAuth2Credentials credentials = new OAuth2Credentials() {