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// Copyright 2017 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.skylarkbuildapi.ProviderApi;
import com.google.devtools.build.lib.syntax.ClassObject;
/**
* Declared Provider (a constructor for {@link InfoInterface}).
*
* <p>Declared providers can be declared either natively ({@link NativeProvider} or in Skylark
* {@link SkylarkProvider}.
*
* <p>{@link Provider} serves both as "type identifier" for declared provider instances and as a
* function that can be called to construct a provider. To the Skylark user, there are "providers"
* and "provider instances"; the former is a Java instance of this class, and the latter is a Java
* instance of {@link InfoInterface}.
*
* <p>Prefer to use {@link Key} as a serializable identifier of {@link Provider}. In particular,
* {@link Key} should be used in all data structures exposed to Skyframe.
*/
@Immutable
public interface Provider extends ProviderApi {
/**
* Has this {@link Provider} been exported? All native providers are always exported. Skylark
* providers are exported if they are assigned to top-level name in a Skylark module.
*/
boolean isExported();
/** Returns a serializable representation of this {@link Provider}. */
Key getKey();
/** Returns a name of this {@link Provider} that should be used in error messages. */
String getPrintableName();
/**
* Returns an error message format string for instances to use for their {@link
* ClassObject#getErrorMessageForUnknownField(String)}.
*
* <p>The format string must contain one {@code '%s'} placeholder for the field name.
*/
default String getErrorMessageFormatForUnknownField() {
return String.format("'%s' object has no attribute '%%s'", getPrintableName());
}
/**
* Returns the location at which provider was defined.
*/
Location getLocation();
/** A serializable representation of {@link Provider}. */
public abstract static class Key {}
}