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// Copyright 2015 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.packages;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* An instance of a given {@code AspectClass} with loaded definition and parameters.
*
* This is an aspect equivalent of {@link Rule} class for build rules.
*
* Note: this class does not have {@code equals()} and {@code hashCode()} redefined, so should
* not be used in SkyKeys.
*/
@Immutable
public final class Aspect implements DependencyFilter.AttributeInfoProvider {
/**
* The aspect definition is a function of the aspect class + its parameters, so we can cache that.
*
* <p>The native aspects are loaded with blaze and are not stateful. Reference equality works fine
* in this case.
*
* <p>Caching of Skylark aspects is not yet implemented.
*/
private static final Map<NativeAspectClass, Map<AspectParameters, AspectDefinition>>
definitionCache = new ConcurrentHashMap<>();
private final AspectDescriptor aspectDescriptor;
private final AspectDefinition aspectDefinition;
private Aspect(
AspectClass aspectClass,
AspectDefinition aspectDefinition,
AspectParameters parameters) {
this.aspectDescriptor = new AspectDescriptor(
Preconditions.checkNotNull(aspectClass),
Preconditions.checkNotNull(parameters));
this.aspectDefinition = Preconditions.checkNotNull(aspectDefinition);
}
public static Aspect forNative(
NativeAspectClass nativeAspectClass, AspectParameters parameters) {
AspectDefinition definition =
definitionCache
.computeIfAbsent(nativeAspectClass, key -> new ConcurrentHashMap<>())
.computeIfAbsent(parameters, nativeAspectClass::getDefinition);
return new Aspect(nativeAspectClass, definition, parameters);
}
public static Aspect forNative(NativeAspectClass nativeAspectClass) {
return forNative(nativeAspectClass, AspectParameters.EMPTY);
}
public static Aspect forSkylark(
SkylarkAspectClass skylarkAspectClass,
AspectDefinition aspectDefinition,
AspectParameters parameters) {
return new Aspect(skylarkAspectClass, aspectDefinition, parameters);
}
/**
* Returns the aspectClass required for building the aspect.
*/
public AspectClass getAspectClass() {
return aspectDescriptor.getAspectClass();
}
/**
* Returns parameters for evaluation of the aspect.
*/
public AspectParameters getParameters() {
return aspectDescriptor.getParameters();
}
public AspectDescriptor getDescriptor() {
return aspectDescriptor;
}
@Override
public String toString() {
return String.format("Aspect %s", aspectDescriptor.toString());
}
public AspectDefinition getDefinition() {
return aspectDefinition;
}
@Override
public boolean isAttributeValueExplicitlySpecified(Attribute attribute) {
// All aspect attributes are implicit.
return false;
}
}
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