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Antlr Syntax Error Handling


In that case, you'll be more interested in the ANTLRErrorListener interface. Matching and control flow continues as if the error had not occurred. The key to this trick is to create a parser rule that consists only of a single empty alt (epsilon set in jargon), then use action code within the rule to Error Reporting As pulse allows users to enter their own boolean expressions (to configure when they receive build notifications), decent error reporting is paramount. http://apexintsoft.com/error-handling/antlr-error-handling-c.php

I'm closing this issue for now since I don't see any action items requiring changes to the runtime from this list. Reload to refresh your session. SemanticException Used to indicate syntactically valid, but nonsensical or otherwise bogus input was found on the input stream. errors where no RecognitionException is available). Discover More

Antlr4 Error Handling

more hot questions question feed about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Science How would/should under-age penalties work? The methods in the lexer base class used to match characters (match et al) throw analogous exceptions. 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.

  1. The system returned: (22) Invalid argument The remote host or network may be down.
  2. RecognitionException A generic recognition problem with the input.
  3. share|improve this answer answered Oct 26 '14 at 13:00 Mouagip 1,8531234 2 I tried this and I confirm that it worked well.

In particular, the methods used to match tokens in the parser base class (match et al) throw MismatchedTokenException. That leaves us with case 4, which is still a little on the cryptic side: $ java NotifyConditionParserTest "failure or (changed and success" Caught error: expecting RIGHT_PAREN, found 'null' It would Or is it inevitable once a certain point in development is reached? Antlr Baseerrorlistener Parameters:recognizer - the parser instance recoverInline TokenrecoverInline(Parserrecognizer) throws RecognitionException This method is called when an unexpected symbol is encountered during an inline match operation, such as Parser.match(int).

Terms Privacy Security Status Help You can't perform that action at this time. Antlr Error Listener Example Because the rule itself is empty, it will add no additional tokens to the set and we can infer that - for our example - the Follow Set it computes will 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()) { How do you combine the elements in Sheldon's T-shirt?

In error recovery mode, Parser.consume() adds symbols to the parse tree by calling ParserRuleContext.addErrorNode(Token) instead of ParserRuleContext.addChild(Token). Antlr Error Handling Example Don't be afraid to do this - generic mechanisms, by their very nature cannot cover all your specialized cases and all the language targets allow you to override the default behaviors. 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. The same is true for offendingSymbol, line, and charPositionInLine.

Antlr Error Listener Example

TokenStreamException Indicates that something went wrong while generating a stream of tokens. Early Termination of Parsing Loops - Finer Grained Recovery There are many situations where a parsing loop aborts prematurely using the standard implementations of recovery. Antlr4 Error Handling Why are static password requirements used so frequently? Antlr Bailerrorstrategy So, how can we implement such a resync?

java error-handling antlr4 share|improve this question edited Aug 9 '13 at 3:58 asked Aug 8 '13 at 17:16 Brad Mace 16.5k968106 add a comment| 3 Answers 3 active oldest votes up navigate here I found another tutorial which might have a solution to your DRY violation: http://jnb.ociweb.com/jnb/jnbJun2008.html Please scroll down to the section titled "Our Parser Grammar". Here is an example that catches an exception for the rule, for an alternate and for a labeled element: rule: a:A B C | D E exception // for alternate catch In fact, all we need do is utilize a simple trick, which is perfectly 'legal' and will do all the calculations for us. Antlr Error Strategy

MismatchedCharException Thrown by CharScanner.match() when it is looking for a character, but finds a different one on the input stream. In other words, a grammar that uses this vocabulary will also use the paraphrase. parsing error-handling antlr share|improve this question edited May 1 '12 at 15:17 asked Apr 30 '12 at 15:45 Burton Samograd 2,8311117 add a comment| 1 Answer 1 active oldest votes up http://apexintsoft.com/error-handling/antlr-c-error-handling.php Please try the request again.

The First set, as its name implies, is the computation of all the tokens that indicate a rule should be selected (or similar decisions), for instance: X ruleY? Antlr4 Throw Exception On Error If anyone knows a way to reuse a rule, let me know! Is there a way I can get it to report errors via exceptions while retaining the useful info in the message?

That way, the parser doesn't have to deal with lexical errors and ask for another token.

I've added some backstory to the question since it appears I might be swimming against the current. –Brad Mace Aug 9 '13 at 4:02 You should just write a You could still rename getCtx() to getContext() for clarity though. Case 4 is certainly the worst of the lot, although the information is accurate it is not exactly user friendly. Antlr4 Bail Error Strategy Matching and control flow continues as if the error had not occurred.

We can now issue errors that will say "While trying to parse class XYZ" rather than "While parsing a script", and within classMember we can apply similar techniques, so that we All Rights Reserved. We recommend upgrading to the latest Safari, Google Chrome, or Firefox. this contact form ANTLR implements good error recovery mechanisms by default within the runtimes of all target languages but in some cases the way a grammar is structured impairs the ability of the algorithms

NoViableAltForCharException The lexer finds an unexpected character; that is, it finds a character that does not begin any alternative in the current decision. If nextToken() sees this, it will convert it to a TokenStreamIOException. Z - the First set for ruleY is the set of tokens that show ruleY should be invoked. When you want to do something special for a particular rule, you implement your own handler for the RecognitionException, and recover in whatever manner seems appropriate.

At runtime, before any rule is invoked from any other rule, the pre-calculated follow set is made available on a stack, and we can use the top set (or indeed any HTH, Ibrahim November 10th, 2006 at 10:46 am Kunnummal says: Hi, Thanks for wonderful tutorial, I have really enjoyed this and got something out from it. SUMMARY of my suggestions for a future version of ANTLR: Always populate the "RecognitionException e" parameter of ANTLRErrorListener.syntaxError (including the OffendingToken) so that we can collect these exceptions for batch handling lexer.removeErrorListeners(); lexer.addErrorListener(DescriptiveErrorListener.INSTANCE); parser.removeErrorListeners(); parser.addErrorListener(DescriptiveErrorListener.INSTANCE); A much more complicated example of an error listener that I use to identify ambiguities which render a grammar non-SLL is the SummarizingDiagnosticErrorListener class in TestPerformance.

Error reporting is covered elsewhere in the Wiki but essentially, if the parser is not already in error recovery mode, then reportError() increments the count of errors it has seen and 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 = TokenStreamIOException Wraps an IOException in a TokenStreamException TokenStreamRecognitionException Wraps a RecognitionException in a TokenStreamException so you can pass it along on a stream. You can directly subclass this if you want to define your own exceptions unless they live more properly under one of the specific exceptions below.

However, before we can examine how to implement your own recovery, we need to know something about how ANTLR recovers from mismatch problems. The documentation for this field reads (for people that don't want to click an extra link): The exception which forced this rule to return. Error Handling and Recovery All syntactic and semantic errors cause parser exceptions to be thrown. A Short Riddle!

All of the above messages are generated using the getMessage method of the exceptions thrown by ANTLR. Brief description: when using root expression containing closure block (...)*, like: testExpression: expr (LOGICAL_OPERATOR expr)*; and parser's error handler is set to org.antlr.v4.runtime.BailErrorStrategy, Antlr parses erroneous input, which is formed in Inspecting the default implementation (in the Java runtime) we find that the match method will call the method recoverFromMismatchedToken() and this in turn will try to use the current Follow set CharStreamException Something bad that happens on the character input stream.

The only bug here is the fact that DefaultErrorStrategy did not parse the input successfully, which is actually a previously known bug that occurs so rarely that it's not a problem Modifying Default Error Messages With Paraphrases The name or definition of a token in your lexer is rarely meaningful to the user of your recognizer or translator. I figured that ANTLR must have a way to retrieve the information, and a little digging uncovered it. It's confusing to differentiate between inline recovery and out-of-rule recovery by populating different parameters to the method rather than using the RecognitionException class already provided - perhaps you can throw a