Add fetch command

This command takes a one or more targets and fetches any external repository
prerequisites that will be needed to build them.

Example usage:

  bazel fetch //foo:bar

If //foo:bar depends on, say, a maven_jar, it'll be downloaded.

--
MOS_MIGRATED_REVID=92279626

4 files changed, 123 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java b/src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java
index b3f5099cd5..fa8cc57033 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java
@@ -14,12 +14,14 @@
 
 package com.google.devtools.build.lib.bazel;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.BlazeVersionInfo;
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
+import com.google.devtools.build.lib.bazel.commands.FetchCommand;
 import com.google.devtools.build.lib.bazel.repository.HttpArchiveFunction;
 import com.google.devtools.build.lib.bazel.repository.HttpDownloadFunction;
 import com.google.devtools.build.lib.bazel.repository.HttpJarFunction;
@@ -35,6 +37,7 @@ import com.google.devtools.build.lib.bazel.rules.workspace.LocalRepositoryRule;
 import com.google.devtools.build.lib.bazel.rules.workspace.MavenJarRule;
 import com.google.devtools.build.lib.bazel.rules.workspace.NewHttpArchiveRule;
 import com.google.devtools.build.lib.bazel.rules.workspace.NewLocalRepositoryRule;
+import com.google.devtools.build.lib.runtime.BlazeCommand;
 import com.google.devtools.build.lib.runtime.BlazeModule;
 import com.google.devtools.build.lib.skyframe.SkyFunctions;
 import com.google.devtools.build.lib.util.Clock;
@@ -96,6 +99,10 @@ public class BazelRepositoryModule extends BlazeModule {
     }
   }
 
+  public Iterable<? extends BlazeCommand> getCommands() {
+    return ImmutableList.of(new FetchCommand());
+  }
+
   @Override
   public ImmutableMap<SkyFunctionName, SkyFunction> getSkyFunctions(BlazeDirectories directories) {
     ImmutableMap.Builder<SkyFunctionName, SkyFunction> builder = ImmutableMap.builder();
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/commands/FetchCommand.java b/src/main/java/com/google/devtools/build/lib/bazel/commands/FetchCommand.java
new file mode 100644
index 0000000000..3bdbc95248
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/bazel/commands/FetchCommand.java
@@ -0,0 +1,109 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.bazel.commands;
+
+import com.google.common.base.Joiner;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import com.google.devtools.build.lib.Constants;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.pkgcache.PackageCacheOptions;
+import com.google.devtools.build.lib.query2.AbstractBlazeQueryEnvironment;
+import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Setting;
+import com.google.devtools.build.lib.query2.engine.QueryException;
+import com.google.devtools.build.lib.query2.engine.QueryExpression;
+import com.google.devtools.build.lib.runtime.BlazeCommand;
+import com.google.devtools.build.lib.runtime.BlazeRuntime;
+import com.google.devtools.build.lib.runtime.Command;
+import com.google.devtools.build.lib.runtime.commands.QueryCommand;
+import com.google.devtools.build.lib.util.AbruptExitException;
+import com.google.devtools.build.lib.util.ExitCode;
+import com.google.devtools.common.options.OptionsParser;
+import com.google.devtools.common.options.OptionsProvider;
+
+/**
+ * Fetches external repositories. Which is so fetch.
+ */
+@Command(name = "fetch",
+    options = { PackageCacheOptions.class },
+    help = "resource:fetch.txt",
+    shortDescription = "Fetches external repositories that are prerequisites to the targets.",
+    allowResidue = true,
+    completion = "label")
+public final class FetchCommand implements BlazeCommand {
+  // TODO(kchodorow): add an option to force-fetch targets, even if they're already downloaded.
+  // TODO(kchodorow): this would be a great time to check for difference and invalidate the upward
+  //                  transitive closure for local repositories.
+  // TODO(kchodorow): prevent fetching from being done during a build.
+
+  @Override
+  public void editOptions(BlazeRuntime runtime, OptionsParser optionsParser) { }
+
+  @Override
+  public ExitCode exec(BlazeRuntime runtime, OptionsProvider options) {
+    if (options.getResidue().isEmpty()) {
+      runtime.getReporter().handle(Event.error(String.format(
+          "missing fetch expression. Type '%s help fetch' for syntax and help",
+          Constants.PRODUCT_NAME)));
+      return ExitCode.COMMAND_LINE_ERROR;
+    }
+
+    try {
+      runtime.setupPackageCache(
+          options.getOptions(PackageCacheOptions.class),
+          runtime.getDefaultsPackageContent());
+    } catch (InterruptedException e) {
+      runtime.getReporter().handle(Event.error("fetch interrupted"));
+      return ExitCode.INTERRUPTED;
+    } catch (AbruptExitException e) {
+      runtime.getReporter().handle(Event.error(null, "Unknown error: " + e.getMessage()));
+      return e.getExitCode();
+    }
+
+    // Querying for all of the dependencies of the targets has the side-effect of populating the
+    // Skyframe graph for external targets, which requires downloading them.
+    String query = Joiner.on(" union ").join(options.getResidue());
+    query = "deps(" + query + ")";
+
+    AbstractBlazeQueryEnvironment<Target> env = QueryCommand.newQueryEnvironment(
+        runtime,
+        true,
+        false,
+        Lists.<String>newArrayList(), 4,
+        Sets.<Setting>newHashSet());
+
+    // 1. Parse query:
+    QueryExpression expr;
+    try {
+      expr = QueryExpression.parse(query, env);
+    } catch (QueryException e) {
+      runtime.getReporter().handle(Event.error(
+          null, "Error while parsing '" + query + "': " + e.getMessage()));
+      return ExitCode.COMMAND_LINE_ERROR;
+    }
+
+    // 2. Evaluate expression:
+    try {
+      env.evaluateQuery(expr);
+    } catch (QueryException e) {
+      // Keep consistent with reportBuildFileError()
+      runtime.getReporter().handle(Event.error(e.getMessage()));
+      return ExitCode.COMMAND_LINE_ERROR;
+    }
+    return ExitCode.SUCCESS;
+  }
+
+
+}
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/commands/fetch.txt b/src/main/java/com/google/devtools/build/lib/bazel/commands/fetch.txt
new file mode 100644
index 0000000000..f7181b3d4f
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/bazel/commands/fetch.txt
@@ -0,0 +1,6 @@
+
+Usage: %{product} %{command} [<option> ...] <targets>
+
+Fetches all external dependencies for the targets given.
+
+%{options}
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
index a675bc8623..21d368c47a 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
@@ -938,8 +938,7 @@ public abstract class SkyframeExecutor implements WalkableGraphFactory {
   EvaluationResult<TargetPatternValue> targetPatterns(Iterable<SkyKey> patternSkyKeys,
       int numThreads, boolean keepGoing, EventHandler eventHandler) throws InterruptedException {
     checkActive();
-    return buildDriver.evaluate(patternSkyKeys, keepGoing, numThreads,
-        eventHandler);
+    return buildDriver.evaluate(patternSkyKeys, keepGoing, numThreads, eventHandler);
   }
 
   /**