Move CredentialProvider up to ClientSettings (#305)

Updates googleapis/google-cloud-java#2034.

This commit should resolve the first 3 bullets in the
linked issue.

Major changes are:
- ClientContext is added to pull together channel, executor, and credentials,
  which are often needed together.
  This change will also simplify future work if more ClientSettings are added.

gax-grpc/src/main/java/com/google/api/gax/grpc/AuthCallable.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.grpc;
+
+import com.google.api.core.ApiFuture;
+import com.google.auth.Credentials;
+import com.google.common.base.Preconditions;
+import io.grpc.CallCredentials;
+import io.grpc.auth.MoreCallCredentials;
+
+/**
+ * Implements the credential insertion for {@link UnaryCallable}.
+ *
+ * <p>Package-private for internal use.
+ */
+class AuthCallable<RequestT, ResponseT> implements FutureCallable<RequestT, ResponseT> {
+  private final FutureCallable<RequestT, ResponseT> callable;
+  private final CallCredentials credentials;
+
+  AuthCallable(FutureCallable<RequestT, ResponseT> callable, Credentials credentials) {
+    this.callable = Preconditions.checkNotNull(callable);
+    this.credentials = MoreCallCredentials.from(Preconditions.checkNotNull(credentials));
+  }
+
+  @Override
+  public ApiFuture<ResponseT> futureCall(RequestT request, CallContext context) {
+    if (context.getCallOptions().getCredentials() == null) {
+      context = context.withCallOptions(context.getCallOptions().withCallCredentials(credentials));
+    }
+    return callable.futureCall(request, context);
+  }
+}

gax-grpc/src/main/java/com/google/api/gax/grpc/BatchingCallSettings.java

@@ -34,11 +34,9 @@
 import com.google.api.gax.retrying.RetrySettings;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableSet;
-import io.grpc.Channel;
 import io.grpc.MethodDescriptor;
 import io.grpc.Status;
 import java.util.Set;
-import java.util.concurrent.ScheduledExecutorService;
 
 /**
  * A settings class to configure a UnaryCallable for calls to an API method that supports batching.
@@ -52,9 +50,10 @@ public final class BatchingCallSettings<RequestT, ResponseT>
   private BatcherFactory<RequestT, ResponseT> batcherFactory;
 
   /** Package-private, for use by UnaryCallable. */
-  UnaryCallable<RequestT, ResponseT> create(Channel channel, ScheduledExecutorService executor) {
-    UnaryCallable<RequestT, ResponseT> baseCallable = createBaseCallable(channel, executor);
-    batcherFactory = new BatcherFactory<>(batchingDescriptor, batchingSettings, executor);
+  UnaryCallable<RequestT, ResponseT> create(ClientContext context) {
+    UnaryCallable<RequestT, ResponseT> baseCallable = createBaseCallable(context);
+    batcherFactory =
+        new BatcherFactory<>(batchingDescriptor, batchingSettings, context.getExecutor());
     return baseCallable.batching(batchingDescriptor, batcherFactory);
   }
 

gax-grpc/src/main/java/com/google/api/gax/grpc/ChannelAndExecutor.java

@@ -41,6 +41,7 @@
  */
 @BetaApi
 @AutoValue
+@Deprecated
 public abstract class ChannelAndExecutor {
   public abstract ScheduledExecutorService getExecutor();
 

gax-grpc/src/main/java/com/google/api/gax/grpc/ClientContext.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright 2017, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.grpc;
+
+import com.google.api.core.BetaApi;
+import com.google.auth.Credentials;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import io.grpc.Channel;
+import io.grpc.ManagedChannel;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.concurrent.ScheduledExecutorService;
+import javax.annotation.Nullable;
+
+/**
+ * Encapsulates client state, including channel, executor, and credentials.
+ *
+ * <p>Unlike {@link ClientSettings} which allows users to configure the client, {@code
+ * ClientContext} is intended to be used in generated code. Most users will not need to use it.
+ */
+@BetaApi
+@AutoValue
+public abstract class ClientContext {
+  public abstract Collection<AutoCloseable> getCloseables();
+
+  public abstract Channel getChannel();
+
+  public abstract ScheduledExecutorService getExecutor();
+
+  @Nullable
+  public abstract Credentials getCredentials();
+
+  static Builder newBuilder() {
+    return new AutoValue_ClientContext.Builder();
+  }
+
+  public static ClientContext create(ClientSettings settings) throws IOException {
+    ImmutableList.Builder<AutoCloseable> closeables = ImmutableList.builder();
+
+    ExecutorProvider executorProvider = settings.getExecutorProvider();
+    final ScheduledExecutorService executor = executorProvider.getExecutor();
+    if (executorProvider.shouldAutoClose()) {
+      closeables.add(
+          new AutoCloseable() {
+            @Override
+            public void close() {
+              executor.shutdown();
+            }
+          });
+    }
+
+    final ManagedChannel channel;
+    ChannelProvider channelProvider = settings.getChannelProvider();
+    if (channelProvider.needsExecutor()) {
+      channel = channelProvider.getChannel(executor);
+    } else {
+      channel = channelProvider.getChannel();
+    }
+    if (channelProvider.shouldAutoClose()) {
+      closeables.add(
+          new AutoCloseable() {
+            @Override
+            public void close() {
+              channel.shutdown();
+            }
+          });
+    }
+    return newBuilder()
+        .setCloseables(closeables.build())
+        .setChannel(channel)
+        .setExecutor(executor)
+        .setCredentials(settings.getCredentialsProvider().getCredentials())
+        .build();
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    public abstract Builder setCloseables(Collection<AutoCloseable> value);
+
+    public abstract Builder setChannel(Channel value);
+
+    public abstract Builder setExecutor(ScheduledExecutorService value);
+
+    public abstract Builder setCredentials(Credentials value);
+
+    public abstract ClientContext build();
+  }
+}

gax-grpc/src/main/java/com/google/api/gax/grpc/ClientSettings.java

@@ -30,10 +30,14 @@
 package com.google.api.gax.grpc;
 
 import com.google.api.core.BetaApi;
+import com.google.api.gax.core.CredentialsProvider;
+import com.google.api.gax.core.NoCredentialsProvider;
 import com.google.api.gax.retrying.RetrySettings;
+import com.google.common.base.MoreObjects;
 import io.grpc.Status;
 import java.io.IOException;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 /**
  * A base settings class to configure a service API class.
@@ -65,14 +69,25 @@ public abstract class ClientSettings {
 
   private final ExecutorProvider executorProvider;
   private final ChannelProvider channelProvider;
+  @Nullable private final CredentialsProvider credentialsProvider;
 
-  /** Constructs an instance of ClientSettings. */
+  @Deprecated
   protected ClientSettings(ExecutorProvider executorProvider, ChannelProvider channelProvider) {
+    this(executorProvider, channelProvider, null);
+  }
+
+  /** Constructs an instance of ClientSettings. */
+  protected ClientSettings(
+      ExecutorProvider executorProvider,
+      ChannelProvider channelProvider,
+      CredentialsProvider credentialsProvider) {
     this.executorProvider = executorProvider;
     this.channelProvider = channelProvider;
+    this.credentialsProvider = credentialsProvider;
   }
 
   /** Gets a channel and an executor for making calls. */
+  @Deprecated
   public final ChannelAndExecutor getChannelAndExecutor() throws IOException {
     return ChannelAndExecutor.create(executorProvider, channelProvider);
   }
@@ -85,20 +100,36 @@ public final ChannelProvider getChannelProvider() {
     return channelProvider;
   }
 
+  @Nullable
+  public final CredentialsProvider getCredentialsProvider() {
+    return credentialsProvider;
+  }
+
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("executorProvider", executorProvider)
+        .add("channelProvider", channelProvider)
+        .add("credentialsProvider", credentialsProvider)
+        .toString();
+  }
+
   public abstract static class Builder {
 
     private ExecutorProvider executorProvider;
     private ChannelProvider channelProvider;
+    private CredentialsProvider credentialsProvider;
 
     /** Create a builder from a ClientSettings object. */
     protected Builder(ClientSettings settings) {
       this.executorProvider = settings.executorProvider;
       this.channelProvider = settings.channelProvider;
+      this.credentialsProvider = settings.credentialsProvider;
     }
 
     protected Builder(InstantiatingChannelProvider channelProvider) {
       this.executorProvider = InstantiatingExecutorProvider.newBuilder().build();
       this.channelProvider = channelProvider;
+      this.credentialsProvider = new NoCredentialsProvider();
     }
 
     /**
@@ -118,6 +149,12 @@ public Builder setChannelProvider(ChannelProvider channelProvider) {
       return this;
     }
 
+    /** Sets the CredentialsProvider to use for getting the channel to make calls with. */
+    public Builder setCredentialsProvider(CredentialsProvider credentialsProvider) {
+      this.credentialsProvider = credentialsProvider;
+      return this;
+    }
+
     /** Gets the ExecutorProvider that was previously set on this Builder. */
     public ExecutorProvider getExecutorProvider() {
       return executorProvider;
@@ -128,6 +165,11 @@ public ChannelProvider getChannelProvider() {
       return channelProvider;
     }
 
+    /** Gets the CredentialsProvider that was previously set on this Builder. */
+    public CredentialsProvider getCredentialsProvider() {
+      return credentialsProvider;
+    }
+
     /** Performs a merge, using only non-null fields */
     protected Builder applyToAllUnaryMethods(
         Iterable<UnaryCallSettings.Builder> methodSettingsBuilders,
@@ -148,5 +190,13 @@ protected Builder applyToAllUnaryMethods(
     }
 
     public abstract ClientSettings build() throws IOException;
+
+    public String toString() {
+      return MoreObjects.toStringHelper(this)
+          .add("executorProvider", executorProvider)
+          .add("channelProvider", channelProvider)
+          .add("credentialsProvider", credentialsProvider)
+          .toString();
+    }
   }
 }

gax-grpc/src/main/java/com/google/api/gax/grpc/InstantiatingChannelProvider.java

@@ -139,6 +139,7 @@ private ManagedChannel createChannel(Executor executor) throws IOException {
    * Gets the credentials which will be used to call the service. If the credentials have not been
    * acquired yet, then they will be acquired when this function is called.
    */
+  @Deprecated
   public Credentials getCredentials() throws IOException {
     return getCredentialsProvider().getCredentials();
   }
@@ -147,6 +148,7 @@ public Credentials getCredentials() throws IOException {
    * The credentials to use in order to call the service. Credentials will not be acquired until
    * they are required.
    */
+  @Deprecated
   public CredentialsProvider getCredentialsProvider() {
     return credentialsProvider;
   }
@@ -261,12 +263,14 @@ public Builder setExecutorProvider(ExecutorProvider executorProvider) {
      * Sets the CredentialsProvider which will acquire the credentials for making calls to the
      * service. Credentials will not be acquired until they are required.
      */
+    @Deprecated
     public Builder setCredentialsProvider(CredentialsProvider credentialsProvider) {
       this.credentialsProvider = credentialsProvider;
       return this;
     }
 
     /** The previously set CredentialsProvider. */
+    @Deprecated
     public CredentialsProvider getCredentialsProvider() {
       return credentialsProvider;
     }

gax-grpc/src/main/java/com/google/api/gax/grpc/OperationCallSettings.java

@@ -33,9 +33,7 @@
 import com.google.longrunning.Operation;
 import com.google.longrunning.OperationsClient;
 import com.google.protobuf.Message;
-import io.grpc.Channel;
 import io.grpc.MethodDescriptor;
-import java.util.concurrent.ScheduledExecutorService;
 import org.threeten.bp.Duration;
 
 /**
@@ -59,12 +57,10 @@ public final Duration getPollingInterval() {
 
   // package-private for internal use.
   OperationCallable<RequestT, ResponseT> createOperationCallable(
-      Channel channel, ScheduledExecutorService executor, OperationsClient operationsClient) {
-    UnaryCallable<RequestT, Operation> initialCallable =
-        initialCallSettings.create(channel, executor);
+      ClientContext context, OperationsClient operationsClient) {
+    UnaryCallable<RequestT, Operation> initialCallable = initialCallSettings.create(context);
     OperationCallable<RequestT, ResponseT> operationCallable =
-        new OperationCallable<>(
-            initialCallable, channel, executor, operationsClient, responseClass, this);
+        new OperationCallable<>(initialCallable, context, operationsClient, responseClass, this);
     return operationCallable;
   }