// 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.pkgcache;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.packages.NoSuchThingException;
import com.google.devtools.build.lib.packages.Target;
import javax.annotation.Nullable;
/**
* An observer of the visitation over a target graph.
*/
public interface TargetEdgeObserver {
/**
* Called when an edge is discovered.
* May be called more than once for the same
* (from, to) pair.
*
* @param from the originating node.
* @param attribute The attribute which defines the edge.
* Non-null iff (from instanceof Rule).
* @param to the target node.
*/
void edge(Target from, Attribute attribute, Target to);
/**
* Called when a Target has a reference to a non-existent target.
*
* @param target the target. May be null (e.g. in the case of an implicit dependency on a
* subincluded file).
* @param to a label reference in the rule, which does not correspond to a valid target.
* @param e the corresponding exception thrown
*/
void missingEdge(@Nullable Target target, Label to, NoSuchThingException e)
throws InterruptedException;
/**
* Called when a node is discovered. May be called
* more than once for the same node.
*
* @param node the target.
*/
void node(Target node);
}