com.facebook.buck.rules.Description.java Source code

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Here is the source code for com.facebook.buck.rules.Description.java

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/*
 * Copyright 2013-present Facebook, Inc.
 *
 * 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.facebook.buck.rules;

import com.facebook.buck.model.Flavor;
import com.facebook.buck.parser.NoSuchBuildTargetException;
import com.facebook.buck.util.MoreStrings;
import com.google.common.base.CaseFormat;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

/**
 * The Source of Truth about a {@link BuildRule}, providing mechanisms to expose the arguments that
 * rules derived from the Buildable take and providing a factory for those BuildRules. It is
 * expected that instances of this class are stateless.
 *
 * @param <T> The object describing the parameters to be passed to the {@link BuildRule}. How this
 *     is processed is described in the class level javadoc of {@link ConstructorArgMarshaller}.
 *
 */
public interface Description<T> {

    static final LoadingCache<Class<? extends Description<?>>, BuildRuleType> BUILD_RULE_TYPES_BY_CLASS = CacheBuilder
            .newBuilder().build(new CacheLoader<Class<? extends Description<?>>, BuildRuleType>() {
                @Override
                public BuildRuleType load(Class<? extends Description<?>> key) throws Exception {
                    return getBuildRuleType(key.getSimpleName());
                }
            });

    /**
     * @return The {@link BuildRuleType} being described.
     */
    static BuildRuleType getBuildRuleType(Class<? extends Description<?>> descriptionClass) {
        return BUILD_RULE_TYPES_BY_CLASS.getUnchecked(descriptionClass);
    }

    @SuppressWarnings("unchecked")
    static BuildRuleType getBuildRuleType(Description<?> description) {
        return getBuildRuleType((Class<? extends Description<?>>) description.getClass());
    }

    static BuildRuleType getBuildRuleType(String descriptionClassName) {
        descriptionClassName = MoreStrings.stripPrefix(descriptionClassName, "Abstract")
                .orElse(descriptionClassName);
        descriptionClassName = MoreStrings.stripSuffix(descriptionClassName, "Description")
                .orElse(descriptionClassName);
        return BuildRuleType.of(CaseFormat.UPPER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, descriptionClassName));
    }

    /**
     * @return An instance of the argument that must later be passed to createBuildRule().
     * @see ConstructorArgMarshaller
     *
     */
    T createUnpopulatedConstructorArg();

    /**
     * Create a {@link BuildRule} for the given {@link BuildRuleParams}. Note that the
     * {@link com.facebook.buck.model.BuildTarget} referred to in the {@code params} contains the
     * {@link Flavor} to create.
     *
     * @param resolver For querying for build rules by their targets.
     * @param args A constructor argument, as returned by {@link #createUnpopulatedConstructorArg()}.
     * @return The {@link BuildRule} that describes the default flavour of the rule being described.
     */
    <A extends T> BuildRule createBuildRule(TargetGraph targetGraph, BuildRuleParams params,
            BuildRuleResolver resolver, A args) throws NoSuchBuildTargetException;
}