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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.devtools.build.lib.events.Location;
import java.io.IOException;
/**
* An index expression ({@code obj[field]}). Not to be confused with a slice expression ({@code
* obj[from:to]}). The object may be either a sequence or an associative mapping (most commonly
* lists and dictionaries).
*/
public final class IndexExpression extends Expression {
private final Expression object;
private final Expression key;
public IndexExpression(Expression object, Expression key) {
this.object = object;
this.key = key;
}
public Expression getObject() {
return object;
}
public Expression getKey() {
return key;
}
@Override
public void prettyPrint(Appendable buffer) throws IOException {
object.prettyPrint(buffer);
buffer.append('[');
key.prettyPrint(buffer);
buffer.append(']');
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
return evaluate(object.eval(env), key.eval(env), env, getLocation());
}
/**
* Retrieves the value associated with a key in the given object.
*
* @throws EvalException if {@code object} is not a list or dictionary
*/
public static Object evaluate(Object object, Object key, Environment env, Location loc)
throws EvalException, InterruptedException {
if (object instanceof SkylarkIndexable) {
Object result = ((SkylarkIndexable) object).getIndex(key, loc);
// TODO(bazel-team): We shouldn't have this convertToSkylark call here. If it's needed at all,
// it should go in the implementations of SkylarkIndexable#getIndex that produce non-Skylark
// values.
return SkylarkType.convertToSkylark(result, env);
} else if (object instanceof String) {
String string = (String) object;
int index = EvalUtils.getSequenceIndex(key, string.length(), loc);
return string.substring(index, index + 1);
} else {
throw new EvalException(
loc,
String.format(
"type '%s' has no operator [](%s)",
EvalUtils.getDataTypeName(object), EvalUtils.getDataTypeName(key)));
}
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
public Kind kind() {
return Kind.INDEX;
}
}
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