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// Copyright 2014 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.analysis;
import com.google.devtools.build.lib.analysis.config.ConfigurationEnvironment;
import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.packages.AbstractAttributeMapper;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.NoSuchThingException;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.syntax.Type;
import java.util.HashSet;
import java.util.Set;
import javax.annotation.Nullable;
/**
* Tool for chasing redirects. This is intended to be used during configuration creation.
*/
public final class RedirectChaser {
/**
* Custom attribute mapper that throws an exception if an attribute's value depends on the
* build configuration.
*/
private static class StaticValuedAttributeMapper extends AbstractAttributeMapper {
public StaticValuedAttributeMapper(Rule rule) {
super(rule.getPackage(), rule.getRuleClassObject(), rule.getLabel(),
rule.getAttributeContainer());
}
/**
* Returns the value of the given attribute.
*
* @throws InvalidConfigurationException if the value is configuration-dependent
*/
public <T> T getAndValidate(String attributeName, Type<T> type)
throws InvalidConfigurationException {
if (getSelectorList(attributeName, type) != null) {
throw new InvalidConfigurationException
("The value of '" + attributeName + "' cannot be configuration-dependent");
}
return super.get(attributeName, type);
}
}
/**
* Follows the 'srcs' attribute of the given label recursively. Keeps repeating as long as the
* labels are either <code>alias</code> or <code>bind</code> rules.
*
* @param env for loading the packages
* @param label the label to start at
* @param name user-meaningful description of the content being resolved
* @return the label which cannot be further resolved
* @throws InvalidConfigurationException if something goes wrong
*/
@Nullable
public static Label followRedirects(ConfigurationEnvironment env, Label label, String name)
throws InvalidConfigurationException, InterruptedException {
Label oldLabel = null;
Set<Label> visitedLabels = new HashSet<>();
visitedLabels.add(label);
try {
while (true) {
Target possibleRedirect = env.getTarget(label);
if (possibleRedirect == null) {
return null;
}
Label newLabel = getBindOrAliasRedirect(possibleRedirect);
if (newLabel == null) {
return label;
}
newLabel = label.resolveRepositoryRelative(newLabel);
oldLabel = label;
label = newLabel;
if (!visitedLabels.add(label)) {
throw new InvalidConfigurationException("The " + name + " points to a rule which "
+ "recursively references itself. The label " + label + " is part of the loop");
}
}
} catch (NoSuchThingException e) {
String prefix = oldLabel == null
? ""
: "in target '" + oldLabel + "': ";
throw new InvalidConfigurationException(prefix + e.getMessage(), e);
}
}
private static Label getBindOrAliasRedirect(Target target)
throws InvalidConfigurationException {
if (!(target instanceof Rule)) {
return null;
}
Rule rule = (Rule) target;
if (!rule.getRuleClass().equals("bind") && !rule.getRuleClass().equals("alias")) {
return null;
}
return new StaticValuedAttributeMapper(rule).getAndValidate("actual", BuildType.LABEL);
}
}
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