Add an "alias" rule.
This will be used to replace RedirectChaser so that we don't need to load packages during configuration creation anymore.
--
MOS_MIGRATED_REVID=121935989
diff --git a/src/main/java/com/google/devtools/build/lib/rules/AliasConfiguredTarget.java b/src/main/java/com/google/devtools/build/lib/rules/AliasConfiguredTarget.java
new file mode 100644
index 0000000..c7d2387
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/AliasConfiguredTarget.java
@@ -0,0 +1,111 @@
+// Copyright 2016 The Bazel Authors. 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.rules;
+
+import com.google.common.collect.ImmutableCollection;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.FileProvider;
+import com.google.devtools.build.lib.analysis.SkylarkProviders;
+import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
+import com.google.devtools.build.lib.collect.nestedset.Order;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.syntax.ClassObject;
+import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
+
+/**
+ * This configured target pretends to be whatever type of target "actual" is, returning its
+ * transitive info providers and target, but returning its own label.
+ *
+ * <p>Transitive info providers can also be overridden.
+ */
+@Immutable
+public final class AliasConfiguredTarget implements ConfiguredTarget, ClassObject {
+ private final ConfiguredTarget configuredTarget;
+ private final ImmutableMap<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider>
+ overrides;
+
+ public AliasConfiguredTarget(ConfiguredTarget actual,
+ ImmutableMap<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider> overrides) {
+ configuredTarget = actual;
+ this.overrides = overrides;
+ }
+
+ @Override
+ public <P extends TransitiveInfoProvider> P getProvider(Class<P> provider) {
+ if (overrides.containsKey(provider)) {
+ return provider.cast(overrides.get(provider));
+ }
+
+ return configuredTarget == null ? null : configuredTarget.getProvider(provider);
+ }
+
+ @Override
+ public Label getLabel() {
+ return configuredTarget.getLabel();
+ }
+
+ @Override
+ public Object get(String providerKey) {
+ return configuredTarget == null ? null : configuredTarget.get(providerKey);
+ }
+
+ @Override
+ public Target getTarget() {
+ return configuredTarget == null ? null : configuredTarget.getTarget();
+ }
+
+ @Override
+ public BuildConfiguration getConfiguration() {
+ return configuredTarget.getConfiguration();
+ }
+
+ /* ClassObject methods */
+
+ @Override
+ public Object getValue(String name) {
+ if (name.equals("label")) {
+ return getLabel();
+ } else if (name.equals("files")) {
+ // A shortcut for files to build in Skylark. FileConfiguredTarget and RunleConfiguredTarget
+ // always has FileProvider and Error- and PackageGroupConfiguredTarget-s shouldn't be
+ // accessible in Skylark.
+ return SkylarkNestedSet.of(Artifact.class, configuredTarget == null
+ ? NestedSetBuilder.<Artifact>emptySet(Order.STABLE_ORDER)
+ : getProvider(FileProvider.class).getFilesToBuild());
+ }
+ return configuredTarget == null ? null : configuredTarget.get(name);
+ }
+
+ @Override
+ public ImmutableCollection<String> getKeys() {
+ ImmutableList.Builder<String> result = ImmutableList.<String>builder().add("label", "files");
+ if (configuredTarget != null) {
+ result.addAll(configuredTarget.getProvider(SkylarkProviders.class).getKeys());
+ }
+ return result.build();
+ }
+
+ @Override
+ public String errorMessage(String name) {
+ // Use the default error message.
+ return null;
+ }
+}
