Introduce CompositeRunfilesSupplier

A convenience used to compose RunfilesSuppliers without having to
deconstruct them.

--
MOS_MIGRATED_REVID=95854609
diff --git a/src/main/java/com/google/devtools/build/lib/actions/BaseSpawn.java b/src/main/java/com/google/devtools/build/lib/actions/BaseSpawn.java
index 62c60e4..9221ae5 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/BaseSpawn.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/BaseSpawn.java
@@ -30,7 +30,6 @@
 import java.util.Map;
 import java.util.Set;
 
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -100,24 +99,6 @@
   public BaseSpawn(List<String> arguments,
       Map<String, String> environment,
       Map<String, String> executionInfo,
-      // TODO(bazel-team): have this always be non-null.
-      @Nullable Artifact runfilesManifest,
-      ActionMetadata action,
-      ResourceSet localResources) {
-    this(arguments, environment, executionInfo,
-        ((runfilesManifest != null)
-            ? ImmutableMap.of(runfilesForFragment(new PathFragment(arguments.get(0))),
-            runfilesManifest)
-            : ImmutableMap.<PathFragment, Artifact>of()),
-        action, localResources);
-  }
-
-  /**
-   * Returns a new Spawn.
-   */
-  public BaseSpawn(List<String> arguments,
-      Map<String, String> environment,
-      Map<String, String> executionInfo,
       ActionMetadata action,
       ResourceSet localResources) {
     this(arguments, environment, executionInfo,
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/CompositeRunfilesSupplier.java b/src/main/java/com/google/devtools/build/lib/analysis/CompositeRunfilesSupplier.java
new file mode 100644
index 0000000..51307b8
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/CompositeRunfilesSupplier.java
@@ -0,0 +1,63 @@
+// Copyright 2015 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.analysis;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Maps;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.RunfilesSupplier;
+import com.google.devtools.build.lib.vfs.PathFragment;
+
+import java.io.IOException;
+import java.util.Map;
+
+/** RunfilesSupplier implementation composing instances. */
+public class CompositeRunfilesSupplier implements RunfilesSupplier {
+
+  private final RunfilesSupplier first;
+  private final RunfilesSupplier second;
+
+  /** Create an instance with {@code first} taking precedence over {@code second}. */
+  public CompositeRunfilesSupplier(RunfilesSupplier first, RunfilesSupplier second) {
+    this.first = Preconditions.checkNotNull(first);
+    this.second = Preconditions.checkNotNull(second);
+  }
+
+  @Override
+  public Iterable<Artifact> getArtifacts() {
+    ImmutableSet.Builder<Artifact> result = ImmutableSet.builder();
+    result.addAll(first.getArtifacts());
+    result.addAll(second.getArtifacts());
+    return result.build();
+  }
+
+  @Override
+  public ImmutableSet<PathFragment> getRunfilesDirs() {
+    ImmutableSet.Builder<PathFragment> result = ImmutableSet.builder();
+    result.addAll(first.getRunfilesDirs());
+    result.addAll(second.getRunfilesDirs());
+    return result.build();
+  }
+
+  @Override
+  public ImmutableMap<PathFragment, Map<PathFragment, Artifact>> getMappings() throws IOException {
+    Map<PathFragment, Map<PathFragment, Artifact>> result = Maps.newHashMap();
+    result.putAll(second.getMappings());
+    result.putAll(first.getMappings());
+    return ImmutableMap.copyOf(result);
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
index c915cae..216a782 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
@@ -16,6 +16,8 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.EmptyRunfilesSupplier;
+import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.syntax.Label;
 
@@ -84,4 +86,13 @@
   @Nullable public Artifact getRunfilesManifest() {
     return runfilesSupport != null ? runfilesSupport.getRunfilesManifest() : null;
   }
+
+  /** Return a {@link RunfilesSupplier} encapsulating runfiles for this tool. */
+  public RunfilesSupplier getRunfilesSupplier() {
+    if (executable != null && runfilesSupport != null) {
+      return new RunfilesSupplierImpl(executable, runfilesSupport.getRunfiles());
+    } else {
+      return EmptyRunfilesSupplier.INSTANCE;
+    }
+  }
 }