antlr4-runtime/src/antlr4/error/BailErrorStrategy.js

JavaScript runtime for ANTLR4

/* Copyright (c) 2012-2022 The ANTLR Project Contributors. All rights reserved.
 * Use is of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */
import InputMismatchException from "./InputMismatchException.js";
import ParseCancellationException from "./ParseCancellationException.js";
import DefaultErrorStrategy from "./DefaultErrorStrategy.js";

/**
 * 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.
 *
 * <p>
 * This error strategy is useful in the following scenarios.</p>
 *
 * <ul>
 * <li><strong>Two-stage parsing:</strong> 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.</li>
 * <li><strong>Silent validation:</strong> 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.</li>
 * </ul>
 *
 * <p>
 * {@code myparser.setErrorHandler(new BailErrorStrategy());}</p>
 *
 * @see Parser//setErrorHandler(ANTLRErrorStrategy)
 * */
export default class BailErrorStrategy extends DefaultErrorStrategy {

    constructor() {
        super();
    }

    /**
     * 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}.
     */
    recover(recognizer, e) {
        let context = recognizer._ctx
        while (context !== null) {
            context.exception = e;
            context = context.parentCtx;
        }
        throw new ParseCancellationException(e);
    }

    /**
     * Make sure we don't attempt to recover inline; if the parser
     * successfully recovers, it won't throw an exception.
     */
    recoverInline(recognizer) {
        this.recover(recognizer, new InputMismatchException(recognizer));
    }

// Make sure we don't attempt to recover from problems in subrules.//
    sync(recognizer) {
        // pass
    }
}