org.antlr.v4.runtime.BailErrorStrategy Maven / Gradle / Ivy
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime;
import org.antlr.v4.runtime.misc.ParseCancellationException;
/**
* This implementation of {@link ANTLRErrorStrategy} responds to syntax errors
* by immediately canceling the parse operation with a
* {@link ParseCancellationException}. The implementation ensures that the
* {@link ParserRuleContext#exception} field is set for all parse tree nodes
* that were not completed prior to encountering the error.
*
*
* This error strategy is useful in the following scenarios.
*
*
* - Two-stage parsing: This error strategy allows the first
* stage of two-stage parsing to immediately terminate if an error is
* encountered, and immediately fall back to the second stage. In addition to
* avoiding wasted work by attempting to recover from errors here, the empty
* implementation of {@link BailErrorStrategy#sync} improves the performance of
* the first stage.
* - Silent validation: When syntax errors are not being
* reported or logged, and the parse result is simply ignored if errors occur,
* the {@link BailErrorStrategy} avoids wasting work on recovering from errors
* when the result will be ignored either way.
*
*
*
* {@code myparser.setErrorHandler(new BailErrorStrategy());}
*
* @see Parser#setErrorHandler(ANTLRErrorStrategy)
*/
public class BailErrorStrategy extends DefaultErrorStrategy {
/** Instead of recovering from exception {@code e}, re-throw it wrapped
* in a {@link ParseCancellationException} so it is not caught by the
* rule function catches. Use {@link Exception#getCause()} to get the
* original {@link RecognitionException}.
*/
@Override
public void recover(Parser recognizer, RecognitionException e) {
for (ParserRuleContext context = recognizer.getContext(); context != null; context = context.getParent()) {
context.exception = e;
}
throw new ParseCancellationException(e);
}
/** Make sure we don't attempt to recover inline; if the parser
* successfully recovers, it won't throw an exception.
*/
@Override
public Token recoverInline(Parser recognizer)
throws RecognitionException
{
InputMismatchException e = new InputMismatchException(recognizer);
for (ParserRuleContext context = recognizer.getContext(); context != null; context = context.getParent()) {
context.exception = e;
}
throw new ParseCancellationException(e);
}
/** Make sure we don't attempt to recover from problems in subrules. */
@Override
public void sync(Parser recognizer) { }
}