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Antlr Default Error Handling


However, the user experience is king, and this hack improves it: $ java NotifyConditionParserTest "failure or (changed and success" Caught error: line 1:32: end of input when expecting a closing parenthesis The general form for specifying an exception handler is: exception [label] catch [exceptionType exceptionVariable] { action } catch ... Not the answer you're looking for? Use this as your "catch all" exception in your main() or other method that invokes a parser, lexer, or treeparser. http://lanprolab.net/error-handling/antlr-4-error-handling.php

Because of this, you must be careful not to use any variables that would have been set by a successful match when an exception is caught. Here is an example that uses a bogus semantic exception (which is a subclass of RecognitionException) to demonstrate blasting out of the lexer: class P extends Parser; { public static void In all cases, the recursive-descent functions on the call stack are exited until an exception handler is encountered for that exception type or one of its base classes (in non-object-oriented languages, First, we might want to disable some of the in-line error handling because of its runtime overhead. http://www.antlr2.org/doc/err.html

Antlr Lexer Error Handling

TokenStreamException Indicates that something went wrong while generating a stream of tokens. Note that IO exceptions are passed back as TokenStreamIOException's regardless of this option. Specifying Parser Exception-Handlers You may attach exception handlers to a rule, an alternative, or a labeled element. In other words, a grammar that uses this vocabulary will also use the paraphrase.

In ANTLR, parser exceptions are thrown when (a) there is a syntax error, (b) there is a failed validating semantic predicate, or (c) you throw a parser exception from an action. We'd love you to try it free today! Thank you for the explanation! Antlr4 Throw Exception On Error It is generally the case that the destination for errors does not change once lexing and parsing has begun, so a refinement on the above solution is to pass the error

where the label is only used for attaching exceptions to labeled elements. Antlr Exception Handling Sometimes you want exceptions to pop out of the lexer--usually when you want to abort the entire parsing process upon syntax error. Technical term to denote opposite of dependency injection? java error-handling antlr4 share|improve this question edited Aug 9 '13 at 3:58 asked Aug 8 '13 at 17:16 Brad Mace 16.2k866104 add a comment| 3 Answers 3 active oldest votes up

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 Antlr Baseerrorlistener Repeating pattern X amount of times in LIKE Translate in-line equations to TeX code (Any Package?) Charging the company I work for to rent from myself Is it possible to write share|improve this answer answered Aug 9 '13 at 2:31 Brad Mace 16.2k866104 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Fix drywall that lost strength due to hanging curtain rod more hot questions question feed lang-java about us tour help blog chat data legal privacy policy work here advertising info mobile

Antlr Exception Handling

See the examples/java/includeFile directory.This a great way to handle nested include files and so on or to try out multiple grammars to see which appears to fit the data. my company I figured that ANTLR must have a way to retrieve the information, and a little digging uncovered it. Antlr Lexer Error Handling MismatchedCharException Thrown by CharScanner.match() when it is looking for a character, but finds a different one on the input stream. Antlr4 Error Handling The best content for your career.

Terms Privacy Security Status Help You can't perform that action at this time. my review here Use this as your "catch all" exception in your main() or other method that invokes a parser, lexer, or treeparser. The typical main or parser invoker has try-catch around the invocation: try { ... } catch(TokenStreamException e) { System.err.println("problem with stream: "+e); } catch(RecognitionException re) { System.err.println("bad input: "+re); } Lexer For example, when parsing a command line for a shell like bash, there’s no point in trying to recover from errors. Antlr Error Listener Example

The information you want is available in the exception that already gets thrown. –Sam Harwell Aug 9 '13 at 11:25 Gentle Reader, if you are like me, you're wondering Creating a whole new ErrorStrategy like Brad Mace suggested is not necessary since the DefaultErrorStrategy produces pretty good error messages by default. TokenStreamIOException Wraps an IOException in a TokenStreamException TokenStreamRecognitionException Wraps a RecognitionException in a TokenStreamException so you can pass it along on a stream. click site In ANTLRWorks 2, I use the following two classes as my primary implementations of this interface: SyntaxErrorListener DescriptiveErrorListener share|improve this answer edited Oct 16 '13 at 14:42 answered Oct 16 '13

The error strategy implementation is responsible for calling Parser.notifyErrorListeners(java.lang.String) as appropriate. Antlr Bailerrorstrategy The generated code currently contains calls to sync(org.antlr.v4.runtime.Parser) after entering the decision state of a closure block ((...)* or (...)+). Not the answer you're looking for?

The first step is to turn off ANTLR's default error handling, so that the errors can be handled by pulse.

ANTLR Exception Hierarchy ANTLR-generated parsers throw exceptions to signal recognition errors or other stream problems. 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 = When an exception is caught, execution resumes at that point. Antlr Error Strategy Please try the request again.

Second, you may specify your own exception handlers in a variety of ways, as described later. if (pce.getCause() instanceof RecognitionException) { RecognitionException re = (RecognitionException)pce.getCause(); ParserRuleContext context = (ParserRuleContext)re.getCtx(); } Edit 2: Based on your other answer, it appears that you don't actually want an exception, but Am I supposed to use something like ((InputMismatchException) pce.getCause()).getCtx().exception to get at the useful error message? –Brad Mace Aug 9 '13 at 2:36 @BradMace I added a bunch more navigate to this website I often use the following listener as a starting point, as it includes the name of the source file with the messages.

Wrap Up Well, that just about does it. Default Exception Handling in the Lexer Normally you want the lexer to keep trying to get a valid token upon lexical error. This allowed the specific case to be handled with a custom message: catch(MismatchedTokenException mte) { if(mte.token.getText() == null) { System.err.println("Caught error: line " Join them; 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

Code above will work correctly (i.e. The options are applied in the grammar file as part of the lexer rules, for example: RIGHT_PAREN options { paraphrase = "a closing parenthesis ')'"; } : ')'; Applying the paraphrases