core: Validate load-balancing policy name early in ManagedChannelBuilder (#12695)

Author: themechbro

api/src/main/java/io/grpc/ManagedChannelBuilder.java

@@ -17,6 +17,7 @@
 package io.grpc;
 
 import com.google.common.base.Preconditions;
+import java.nio.channels.Channel;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
@@ -269,7 +270,7 @@ public T useTransportSecurity() {
 
   /**
    * Sets the default load-balancing policy that will be used if the service config doesn't specify
-   * one.  If not set, the default will be the "pick_first" policy.
+   * one. If not set, the default will be the "pick_first" policy.
    *
    * <p>Policy implementations are looked up in the
    * {@link LoadBalancerRegistry#getDefaultRegistry default LoadBalancerRegistry}.
@@ -283,9 +284,8 @@ public T useTransportSecurity() {
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771")
   public T defaultLoadBalancingPolicy(String policy) {
     Preconditions.checkArgument(
-      LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null,
-      "invalid load balancing policy %s", policy
-    );
+        LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null,
+        "invalid load balancing policy %s", policy);
     throw new UnsupportedOperationException();
   }
 

core/src/main/java/io/grpc/internal/ManagedChannelImplBuilder.java

@@ -213,11 +213,11 @@ public static ManagedChannelBuilder<?> forTarget(String target) {
   private boolean recordRetryMetrics = true;
   private boolean tracingEnabled = true;
   List<MetricSink> metricSinks = new ArrayList<>();
-
   /**
    * An interface for Transport implementors to provide the {@link ClientTransportFactory}
    * appropriate for the channel.
    */
+
   public interface ClientTransportFactoryBuilder {
     ClientTransportFactory buildClientTransportFactory();
   }
@@ -448,12 +448,9 @@ public ManagedChannelImplBuilder defaultLoadBalancingPolicy(String policy) {
         "directServerAddress is set (%s), which forbids the use of load-balancing policy",
         directServerAddress);
     Preconditions.checkArgument(policy != null, "policy cannot be null");
-
-    Preconditions.checkArgument(
-      LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null,
-      "invalid load-balancing policy %s", policy
-    );
-
+  Preconditions.checkArgument( // (4 spaces)
+        LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null, // (8 spaces)
+        "invalid load-balancing policy %s", policy); // (8 spaces)
     this.defaultLbPolicy = policy;
     return this;
   }