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Alias.java
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Alias.java
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// 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.devtools.build.lib.actions.ActionConflictException;
import com.google.devtools.build.lib.analysis.BaseRuleClasses;
import com.google.devtools.build.lib.analysis.ConfiguredTarget;
import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
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.packages.BuildType;
import com.google.devtools.build.lib.packages.RawAttributeMapper;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.util.FileTypeSet;
/**
* Implementation of the <code>alias</code> rule.
*/
public class Alias implements RuleConfiguredTargetFactory {
public static final String RULE_NAME = "alias";
private static final String ACTUAL_ATTRIBUTE_NAME = "actual";
@Override
public ConfiguredTarget create(RuleContext ruleContext)
throws InterruptedException, RuleErrorException, ActionConflictException {
ConfiguredTarget actual = (ConfiguredTarget) ruleContext.getPrerequisite("actual");
// TODO(b/129045294): Remove the logic below completely when repo is deleted.
if (ruleContext.getLabel().getCanonicalForm().startsWith("@bazel_tools//platforms")) {
throw ruleContext.throwWithRuleError(
"Constraints from @bazel_tools//platforms have been "
+ "removed. Please use constraints from @platforms repository embedded in "
+ "Bazel, or preferably declare dependency on "
+ "https://github.com/bazelbuild/platforms. See "
+ "https://github.com/bazelbuild/bazel/issues/8622 for details.");
}
return AliasConfiguredTarget.create(ruleContext, actual, ruleContext.getVisibility());
}
/**
* Rule definition.
*/
public static class AliasRule implements RuleDefinition {
@Override
public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment environment) {
// If transitions are added here, AspectFunction should be modified to follow all
// configurations along alias chains.
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 -->*/
.removeAttribute("licenses")
.removeAttribute("distribs")
.removeAttribute(":action_listener")
.add(
attr(ACTUAL_ATTRIBUTE_NAME, LABEL)
.allowedFileTypes(FileTypeSet.ANY_FILE)
.allowedRuleClasses(ANY_RULE)
.mandatory())
.canHaveAnyProvider()
// Aliases themselves do not need toolchains or an execution platform, so this is fine.
// The actual target will resolve platforms and toolchains with no issues regardless of
// this setting. In some circumstances an alias directly needs the platform:
// - when it has a select() on a constraint_setting, or
// - when it has a target_compatible_with attribute.
// Special-case enable those instances too.
.toolchainResolutionMode(
(rule) -> {
RawAttributeMapper attr = RawAttributeMapper.of(rule);
return ((attr.has(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE)
&& !attr.get(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE, BuildType.LABEL_LIST)
.isEmpty())
|| (attr.has(RuleClass.TARGET_COMPATIBLE_WITH_ATTR)
&& !attr.get(RuleClass.TARGET_COMPATIBLE_WITH_ATTR, BuildType.LABEL_LIST)
.isEmpty()));
})
.build();
}
@Override
public Metadata getMetadata() {
return Metadata.builder()
.name(RULE_NAME)
.factoryClass(Alias.class)
.ancestors(BaseRuleClasses.NativeBuildRule.class)
.build();
}
}
}
/*<!-- #BLAZE_RULE (NAME = alias, 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>
and <code>test_suite</code> cannot be aliased.
</p>
<p>
Aliasing may be of help in large repositories where renaming a target would require making
changes to lots of files. You can also use alias rule to store a
<a href="${link select}">select</a> function call if you want to reuse that logic for
multiple targets.
</p>
<p>
The alias rule has its own visibility declaration. In all other respects, it behaves
like the rule it references (e.g. testonly <em>on the alias</em> is ignored; the testonly-ness
of the referenced rule is used instead) with some minor exceptions:
<ul>
<li>
Tests are not run if their alias is mentioned on the command line. To define an alias
that runs the referenced test, use a <a href="#test_suite"><code>test_suite</code></a>
rule with a single target in its <a href="#test_suite.tests"><code>tests</code></a>
attribute.
</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 -->*/