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// 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.syntax;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/** Syntax node for lists comprehension expressions. */
public final class ListComprehension extends AbstractComprehension {
private final Expression outputExpression;
public ListComprehension(List<Clause> clauses, Expression outputExpression) {
super(clauses, outputExpression);
this.outputExpression = outputExpression;
}
@Override
protected char openingBracket() {
return '[';
}
@Override
protected char closingBracket() {
return ']';
}
public Expression getOutputExpression() {
return outputExpression;
}
@Override
protected void printExpressions(Appendable buffer) throws IOException {
outputExpression.prettyPrint(buffer);
}
/** Builder for {@link ListComprehension}. */
public static class Builder extends AbstractBuilder {
private Expression outputExpression;
public Builder setOutputExpression(Expression outputExpression) {
this.outputExpression = outputExpression;
return this;
}
@Override
public ListComprehension build() {
Preconditions.checkState(!clauses.isEmpty());
return new ListComprehension(clauses, Preconditions.checkNotNull(outputExpression));
}
}
@Override
OutputCollector createCollector(Environment env) {
return new ListOutputCollector();
}
/**
* Helper class that collects the intermediate results of the {@code ListComprehension} and
* provides access to the resulting {@code List}.
*/
private final class ListOutputCollector implements OutputCollector {
private final List<Object> result;
ListOutputCollector() {
result = new ArrayList<>();
}
@Override
public Location getLocation() {
return ListComprehension.this.getLocation();
}
@Override
public List<Clause> getClauses() {
return ListComprehension.this.getClauses();
}
@Override
public void evaluateAndCollect(Environment env) throws EvalException, InterruptedException {
result.add(outputExpression.eval(env));
}
@Override
public Object getResult(Environment env) throws EvalException {
return MutableList.copyOf(env, result);
}
}
}
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