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

1 files changed, 120 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/Alias.java b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
new file mode 100644
index 0000000000..540bcc953b
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
@@ -0,0 +1,120 @@
+// 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 static com.google.devtools.build.lib.packages.Attribute.ANY_RULE;
+import static com.google.devtools.build.lib.packages.Attribute.attr;
+import static com.google.devtools.build.lib.packages.BuildType.LABEL;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.analysis.BaseRuleClasses;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.LicensesProvider;
+import com.google.devtools.build.lib.analysis.LicensesProviderImpl;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.RuleDefinition;
+import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.analysis.VisibilityProvider;
+import com.google.devtools.build.lib.analysis.VisibilityProviderImpl;
+import com.google.devtools.build.lib.packages.RuleClass;
+import com.google.devtools.build.lib.packages.RuleClass.Builder;
+import com.google.devtools.build.lib.util.FileTypeSet;
+
+/**
+ * Implementation of the <code>alias</code> rule.
+ */
+public class Alias implements RuleConfiguredTargetFactory {
+  @Override
+  public ConfiguredTarget create(RuleContext ruleContext) throws InterruptedException {
+    ConfiguredTarget actual = (ConfiguredTarget) ruleContext.getPrerequisite("actual", Mode.TARGET);
+    return new AliasConfiguredTarget(
+        actual,
+        ImmutableMap.of(
+            AliasProvider.class, AliasProvider.fromAliasRule(ruleContext.getLabel(), actual),
+            VisibilityProvider.class, new VisibilityProviderImpl(ruleContext.getVisibility()),
+            LicensesProvider.class, LicensesProviderImpl.of(ruleContext)));
+  }
+
+  /**
+   * Rule definition.
+   */
+  public static class AliasRule implements RuleDefinition {
+    @Override
+    public RuleClass build(Builder builder, RuleDefinitionEnvironment environment) {
+      return builder
+          /*<!-- #BLAZE_RULE(alias).ATTRIBUTE(actual) -->
+          The target this alias refers to. It does not need to be a rule, it can also be an input
+          file.
+          <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
+          .add(attr("actual", LABEL)
+              .allowedFileTypes(FileTypeSet.ANY_FILE)
+              .allowedRuleClasses(ANY_RULE)
+              .mandatory())
+          .build();
+    }
+
+    @Override
+    public Metadata getMetadata() {
+      return Metadata.builder()
+          .name("alias")
+          .factoryClass(Alias.class)
+          .ancestors(BaseRuleClasses.BaseRule.class)
+          .build();
+    }
+  }
+}
+
+/*<!-- #BLAZE_RULE (NAME = alias, TYPE = OTHER, FAMILY = General)[GENERIC_RULE] -->
+
+<p>
+  The <code>alias</code> rule creates another name a rule can be referred to as.
+</p>
+
+<p>
+  Aliasing only works for "regular" targets. In particular, <code>package_group</code>,
+    <code>config_setting</code> and <code>test_suite</code> rules cannot be aliased.
+</p>
+
+<p>
+  The alias rule has its own visibility and license declaration. In all other respects, it behaves
+  like the rule it references with some minor exceptions:
+
+  <ul>
+    <li>
+      Tests are not run if their alias is mentioned on the command line
+    </li>
+    <li>
+      When defining environment groups, the aliases to <code>environment</code> rules are not
+      supported. They are not supported in the <code>--target_environment</code> command line
+      option, either.
+    </li>
+  </ul>
+</p>
+
+<h4 id="alias_example">Examples</h4>
+
+<pre class="code">
+filegroup(
+    name = "data",
+    srcs = ["data.txt"],
+)
+
+alias(
+    name = 'other',
+    actual = ':data',
+)
+</pre>
+
+<!-- #END_BLAZE_RULE -->*/