Antlr Default Error Handling
Contents |
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the antlr lexer error handling workings and policies of this site About Us Learn more about Stack antlr exception handling Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs antlr4 error handling Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; antlr error listener example it only takes a minute: Sign up Handling errors in ANTLR4 up vote 24 down vote favorite 10 The default behavior when the parser doesn't know what to do is to print messages to the terminal like: line 1:23 missing DECIMAL at '}' This is a good message, but in the wrong place. I'd rather receive this as an
Antlr4 Throw Exception On Error
exception. I've tried using the BailErrorStrategy, but this throws a ParseCancellationException without a message (caused by a InputMismatchException, also without a message). Is there a way I can get it to report errors via exceptions while retaining the useful info in the message? Here's what I'm really after--I typically use actions in rules to build up an object: dataspec returns [DataExtractor extractor] @init { DataExtractorBuilder builder = new DataExtractorBuilder(layout); } @after { $extractor = builder.create(); } : first=expr { builder.addAll($first.values); } (COMMA next=expr { builder.addAll($next.values); })* EOF ; expr returns [List
ANTLRErrorStrategy All Known Implementing Classes: BailErrorStrategy, DefaultErrorStrategy antlr bailerrorstrategy public interface ANTLRErrorStrategy The interface for defining strategies to deal antlr error strategy with syntax errors encountered during a parse by ANTLR-generated parsers. We distinguish between three different kinds http://stackoverflow.com/questions/18132078/handling-errors-in-antlr4 of errors: The parser could not figure out which path to take in the ATN (none of the available alternatives could possibly match) The current input does not match what we were looking for http://www.antlr.org/api/Java/org/antlr/v4/runtime/ANTLRErrorStrategy.html A predicate evaluated to false Implementations of this interface report syntax errors by calling Parser.notifyErrorListeners(java.lang.String). TODO: what to do about lexers Method Summary Methods Modifier and Type Method and Description boolean inErrorRecoveryMode(Parserrecognizer) Tests whether or not recognizer is in the process of recovering from an error. void recover(Parserrecognizer, RecognitionExceptione) This method is called to recover from exception e. Token recoverInline(Parserrecognizer) This method is called when an unexpected symbol is encountered during an inline match ope
Gadgets About Confluence Log in ANTLR 3PagesBlogChild pagesANTLR v3 documentationError reporting and recoveryBrowse pagesConfigureSpace tools Attachments (0) Page History Page Information Resolved comments Link https://theantlrguy.atlassian.net/wiki/display/ANTLR3/Error+reporting+and+recovery to this Page… View in Hierarchy View Source Export to PDF https://www.safaribooksonline.com/library/view/the-definitive-antlr/9781941222621/f_0065.html Export to Word Pages ANTLR 3 Wiki Home ANTLR v3 documentation Skip to end of banner JIRA links Go to start of banner Error reporting and recovery Skip to end of metadata Created by Terence Parr [Administrator], last modified on Jan 20, 2009 Go to start error handling of metadata Default Error Reporting Behavior Errors encountered during lexing and parsing are passed to the displayRecognitionError() method. This method has access to the exception that holds information about the error, and uses it to compose an error string that is then passed to the emitErrorMessage() method. The default behavior of emitErrorMessage() is to print the error string antlr default error to System.err. Custom Error Reporting To change the default error reporting behavior, override either the displayRecognitionError() or the emitErrorMessage() methods in the lexer and parser. If you need to change the format of the error message or obtain extra information, such as the error location, then you must override displayRecognitionError(). If all you need to do is change where errors are reported and are happy to keep the error message itself unchanged, then you can just override emitErrorMessage() instead. Here is an example of overriding displayRecognitionError(): @members { public void displayRecognitionError(String[] tokenNames, RecognitionException e) { String hdr = getErrorHeader(e); String msg = getErrorMessage(e, tokenNames); // Now do something with hdr and msg... } } Rather than simply printing errors to a stream, another common approach is to store them in a data structure for use later in the application. An example of this approach is to append errors to a List within the lexer and parser and to provide a public method to allow access to the list: @members { private List Attributes and Actions Close The Definitive ANTLR 4 Reference, 2nd Edition by Terence Parr Published by Pragmatic Bookshelf The Definitive ANTLR 4 Reference Copyright For the Best Reading Experience... Table of Contents Early Praise for The Definitive ANTLR 4 Reference Acknowledgments Welcome Aboard! Who Is This Book For? What’s So Cool About ANTLR V4? What’s in This Book? Learning More About ANTLR Online Part 1: Introducing ANTLR and Computer Languages Chapter 1: Meet ANTLR Chapter 2: The Big Picture Chapter 3: A Starter ANTLR Project Chapter 4: A Quick Tour Part 2: Developing Language Applications with ANTLR Grammars Chapter 5: Designing Grammars Chapter 6: Exploring Some Real Grammars Chapter 7: Decoupling Grammars from Application-Specific Code Chapter 8: Building Some Real Language Applications Part 3: Advanced Topics Chapter 9: Error Reporting and Recovery Chapter 10: Attributes and Actions Chapter 11: Altering the Parse with Semantic Predicates Chapter 12: Wielding Lexical Black Magic Part 4: ANTLR Reference Chapter 13: Exploring the Runtime API Chapter 14: Removing Direct Left Recursion Chapter 15: Grammar Reference Appendix 1: Bibliography You May Be Interested In… Altering ANTLR’s Error Handling Strategy The default error handling mechanism works very well, but there are a few atypical situations in which we might want to alter it. First, we might want to disable some of the in-line error handling because of its runtime overhead. Second, we might want to bail out of the parser upon the first syntax error. For example, when parsing a command line for a shell like bash, there’s no point in trying to recover from errors. We can’t risk executing that command anyway, so the parser can bail out at the first sign of trouble. To explore the error handling strategy, take a look at interface ANTLRErrorStrategy and its concrete implementation class DefaultErrorStrategy. That class holds everything associated with ... The best content for your career. Discover unlimited learning on demand for around $1/day. Get 10 Days Free Recommended for you Prev Error Alternatives Next Chapter 10: Attributes and Actions Explore Tour Pricing Enterprise Government Education Queue App Learn Blog Contact Careers Press Resources Support Twitter GitHub Facebook LinkedIn Terms of Service Membership Agreement Privacy Policy Copyright © 2016 Safari Books Online.