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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.skyframe;
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.NestedSet;
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.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.packages.NoSuchTargetException;
import com.google.devtools.build.skyframe.SkyValue;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import javax.annotation.Nullable;
/**
* A <i>transitive</i> target reference that, when built in skyframe, loads the entire
* transitive closure of a target.
*
* <p>Note that this class drops transitive targets during serialization!
*/
@Immutable
@ThreadSafe
public class TransitiveTargetValue implements SkyValue {
// Non-final for serialization purposes.
private NestedSet<Label> transitiveTargets;
@Nullable private NestedSet<Label> transitiveRootCauses;
@Nullable private NoSuchTargetException errorLoadingTarget;
private NestedSet<Class<? extends BuildConfiguration.Fragment>> transitiveConfigFragments;
private TransitiveTargetValue(
NestedSet<Label> transitiveTargets,
@Nullable NestedSet<Label> transitiveRootCauses,
@Nullable NoSuchTargetException errorLoadingTarget,
NestedSet<Class<? extends BuildConfiguration.Fragment>> transitiveConfigFragments) {
this.transitiveTargets = transitiveTargets;
this.transitiveRootCauses = transitiveRootCauses;
this.errorLoadingTarget = errorLoadingTarget;
this.transitiveConfigFragments = transitiveConfigFragments;
}
private void writeObject(ObjectOutputStream out) throws IOException {
// Deliberately do not write out transitiveTargets. There is a lot of those and they drive
// serialization costs through the roof, both in terms of space and of time.
// TODO(bazel-team): Deal with this properly once we have efficient serialization of NestedSets.
out.writeObject(transitiveRootCauses);
out.writeObject(errorLoadingTarget);
out.writeObject(transitiveConfigFragments);
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
// TODO(bazel-team): Deal with transitiveTargets properly.
transitiveTargets = NestedSetBuilder.emptySet(Order.STABLE_ORDER);
transitiveRootCauses = (NestedSet<Label>) in.readObject();
errorLoadingTarget = (NoSuchTargetException) in.readObject();
transitiveConfigFragments =
(NestedSet<Class<? extends BuildConfiguration.Fragment>>) in.readObject();
}
static TransitiveTargetValue unsuccessfulTransitiveLoading(
NestedSet<Label> transitiveTargets,
NestedSet<Label> rootCauses, @Nullable NoSuchTargetException errorLoadingTarget,
NestedSet<Class<? extends BuildConfiguration.Fragment>> transitiveConfigFragments) {
return new TransitiveTargetValue(
transitiveTargets, rootCauses, errorLoadingTarget, transitiveConfigFragments);
}
static TransitiveTargetValue successfulTransitiveLoading(
NestedSet<Label> transitiveTargets,
NestedSet<Class<? extends BuildConfiguration.Fragment>> transitiveConfigFragments) {
return new TransitiveTargetValue(transitiveTargets, null, null, transitiveConfigFragments);
}
/** Returns the error, if any, from loading the target. */
@Nullable
public NoSuchTargetException getErrorLoadingTarget() {
return errorLoadingTarget;
}
/** Returns the targets that were transitively loaded. */
public NestedSet<Label> getTransitiveTargets() {
return transitiveTargets;
}
/** Returns the root causes, if any, of why targets weren't loaded. */
@Nullable
public NestedSet<Label> getTransitiveRootCauses() {
return transitiveRootCauses;
}
/**
* Returns the set of {@link
* com.google.devtools.build.lib.analysis.config.BuildConfiguration.Fragment} classes required to
* configure a rule's transitive closure. These are used to instantiate the right {@link
* ConfigurationFragmentValue} instances for a rule's {@link BuildConfigurationValue}.
*
* <p>This provides the basis for rule-scoped configurations. For example, Java-related build
* flags have nothing to do with C++. So changing a Java flag shouldn't invalidate a C++ rule
* (unless it has transitive dependencies on other Java rules). Likewise, a C++ rule shouldn't
* fail because the Java configuration doesn't recognize the chosen architecture.
*
* <p>The general principle is that a rule can be influenced by the configuration parameters it
* directly uses and the configuration parameters its transitive dependencies use (since it
* reads its dependencies as part of analysis). So we need to 1) determine which configuration
* fragments provide these parameters, 2) load those fragments, then 3) create a configuration
* from them to feed the rule's configured target. This provides the first step.
*
* <p>See
* {@link com.google.devtools.build.lib.packages.RuleClass.Builder#requiresConfigurationFragments}
*/
public NestedSet<Class<? extends BuildConfiguration.Fragment>> getTransitiveConfigFragments() {
return transitiveConfigFragments;
}
}
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