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// Copyright 2018 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.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.packages.NativeProvider.NativeKey;
import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
import com.google.devtools.build.lib.syntax.EvalException;
import javax.annotation.Nullable;
/**
* Base class for declared providers {@see Provider} defined in native code.
*
* <p>Every subclass of {@link BuiltinProvider} corresponds to a single declared
* provider. This is enforced by final {@link #equals(Object)} and {@link #hashCode()}.
*
* <p>Implementations of native declared providers should subclass this class, and define a method
* in the subclass definition to create instances of its corresponding Info object. The method
* should be annotated with {@link SkylarkCallable} with {@link SkylarkCallable#selfCall} set to
* true, and with {@link SkylarkConstructor} for the info type it constructs.
*/
@Immutable
public abstract class BuiltinProvider<T extends Info> implements Provider {
private final NativeKey key;
private final String name;
private final Class<T> valueClass;
public Class<T> getValueClass() {
return valueClass;
}
public BuiltinProvider(String name, Class<T> valueClass) {
@SuppressWarnings("unchecked")
Class<? extends BuiltinProvider<?>> clazz = (Class<? extends BuiltinProvider<?>>) getClass();
key = new NativeKey(name, clazz);
this.name = name;
this.valueClass = valueClass;
}
/**
* equals() implements singleton class semantics.
*/
@Override
public final boolean equals(@Nullable Object other) {
return other != null && this.getClass().equals(other.getClass());
}
/**
* hashCode() implements singleton class semantics.
*/
@Override
public final int hashCode() {
return getClass().hashCode();
}
@Override
public boolean isExported() {
return true;
}
@Override
public NativeKey getKey() {
return key;
}
@Override
public Location getLocation() {
return Location.BUILTIN;
}
@Override
public String getPrintableName() {
return name;
}
@Override
public void repr(SkylarkPrinter printer) {
printer.append("<function " + getPrintableName() + ">");
}
/**
* Convenience method for subclasses of this class to throw a consistent error when
* a provider is unable to be constructed from skylark.
*/
protected T throwUnsupportedConstructorException(Location loc) throws EvalException {
throw new EvalException(
loc, String.format("'%s' cannot be constructed from Skylark", getPrintableName()));
}
/**
* Returns the identifier of this provider.
*/
public SkylarkProviderIdentifier id() {
return SkylarkProviderIdentifier.forKey(getKey());
}
}
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