From 03300cb2debb6b31f23d88f0f99eabcbe9ce4069 Mon Sep 17 00:00:00 2001
From: Eric Anderson <ejona@google.com>
Date: Fri, 7 Dec 2018 14:34:11 -0800
Subject: [PATCH] alts: Eagerly add interceptor in GoogleDefaultChannelBuilder

This allows calling build() multiple times as well as prevents other
interceptors from being able to detect that we've implemented
CallCredential attachment via an interceptor. (Previously they could
have set their own CallCredentials which would have overridden the
default creds.)
---
 .../alts/GoogleDefaultChannelBuilder.java     | 26 ++++++++-----------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/alts/src/main/java/io/grpc/alts/GoogleDefaultChannelBuilder.java b/alts/src/main/java/io/grpc/alts/GoogleDefaultChannelBuilder.java
index 8a5ece69a2..0c66b99af1 100644
--- a/alts/src/main/java/io/grpc/alts/GoogleDefaultChannelBuilder.java
+++ b/alts/src/main/java/io/grpc/alts/GoogleDefaultChannelBuilder.java
@@ -60,6 +60,17 @@ public final class GoogleDefaultChannelBuilder
     delegate = NettyChannelBuilder.forTarget(target);
     InternalNettyChannelBuilder.setProtocolNegotiatorFactory(
         delegate(), new ProtocolNegotiatorFactory());
+    @Nullable CallCredentials credentials = null;
+    Status status = Status.OK;
+    try {
+      credentials = MoreCallCredentials.from(GoogleCredentials.getApplicationDefault());
+    } catch (IOException e) {
+      status =
+          Status.UNAUTHENTICATED
+              .withDescription("Failed to get Google default credentials")
+              .withCause(e);
+    }
+    delegate().intercept(new GoogleDefaultInterceptor(credentials, status));
   }
 
   /** "Overrides" the static method in {@link ManagedChannelBuilder}. */
@@ -77,21 +88,6 @@ public final class GoogleDefaultChannelBuilder
     return delegate;
   }
 
-  @Override
-  public ManagedChannel build() {
-    @Nullable CallCredentials credentials = null;
-    Status status = Status.OK;
-    try {
-      credentials = MoreCallCredentials.from(GoogleCredentials.getApplicationDefault());
-    } catch (IOException e) {
-      status =
-          Status.UNAUTHENTICATED
-              .withDescription("Failed to get Google default credentials")
-              .withCause(e);
-    }
-    return delegate().intercept(new GoogleDefaultInterceptor(credentials, status)).build();
-  }
-
   @VisibleForTesting
   GoogleDefaultProtocolNegotiator getProtocolNegotiatorForTest() {
     return negotiatorForTest;