Antlr Custom Error Handling
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here for a quick overview of the site Help Center Detailed answers to any questions you might have antlr lexer error handling Meta Discuss the workings and policies of this site About Us antlr exception handling Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads antlr4 error handling with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, antlr error listener just like you, helping each other. 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 is to print messages to the terminal like: line 1:23 missing DECIMAL at '}' This is a good message,
Antlr Error Listener Example
but in the wrong place. I'd rather receive this as an 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
Gadgets About Confluence Log in ANTLR 3PagesBlogChild pagesArticlesCustom Syntax Error RecoveryBrowse pagesConfigureSpace tools Attachments (0) Page History Page Information Resolved comments Link to this Page… View in Hierarchy View Source Export to PDF Export to
Antlr4 Throw Exception On Error
Word Pages ANTLR 3 Wiki Home Articles Skip to end of banner JIRA antlr baseerrorlistener links Go to start of banner Custom Syntax Error Recovery Skip to end of metadata Created by Unknown User (jimi@idle.ws), last antlr error strategy modified on Oct 05, 2010 Go to start of metadata Custom Syntax Error Recovery An important part of a robust and useful parser is the behavior it exhibits when the next token in its http://stackoverflow.com/questions/18132078/handling-errors-in-antlr4 incoming token stream is not one that the grammar specifies should be there. This is generally known as a syntax error. Here we look at how ANTLR recovers from the various mismatch cases and what techniques you can use to override or influence that recovery. The examples shown use the Java language, but the same techniques should apply to all ANTLR targets. ANTLR implements good error recovery mechanisms by https://theantlrguy.atlassian.net/wiki/display/ANTLR3/Custom+Syntax+Error+Recovery default within the runtimes of all target languages but in some cases the way a grammar is structured impairs the ability of the algorithms to recover to exactly where you might expect or wish. Sometimes your grammar rules cause a loop in a parsing rule to be exited earlier than you would expect or want; sometimes when a certain construct is in error you want to skip everything up to the end of that construct instead of resuming at wherever ANTLR sees a token that looks like it is a valid recovery point. There are many reasons you may wish to influence or override the standard recovery behavior. However, before we can examine how to implement your own recovery, we need to know something about how ANTLR recovers from mismatch problems. Recognition Exception Once a mismatch is detected, the generated code causes the target language equivalent of the Java Runtime's RecognitionException to be thrown or otherwise handled. If you examine a method generated for a parser rule in the Java target, you will see that the rule logic is encapsulated within a try {} catch {} block, which catches RecognitionException: Generated Exception Handler catch (RecognitionException re) { reportError(re); recover(input,re); } You can see that t
Gadgets About Confluence Log in ANTLR 3PagesBlogChild pagesANTLR v3 documentationError reporting and recoveryBrowse pagesConfigureSpace tools Attachments (0) Page History Page Information Resolved comments Link to this Page… https://theantlrguy.atlassian.net/wiki/display/ANTLR3/Error+reporting+and+recovery View in Hierarchy View Source Export to PDF 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 of metadata Default Error Reporting Behavior Errors error handling 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 to System.err. Custom Error Reporting To change the default error antlr error listener 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