Antlr 4 Error Handling
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Antlr Error Listener Example
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Antlr4 Bailerrorstrategy
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 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 antlr error handling example 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
no alternative of a production in either the parser or lexer, then a NoViableAltException is thrown. The methods in the lexer base class used
Antlr4 Throw Exception On Error
to match characters (match et al) throw analogous exceptions. ANTLR will generate antlr error strategy default error-handling code, or you may specify your own exception handlers. Either case results (where supported by the antlr4 lexer error handling language) in the creation of a try/catch block. Such try{} blocks surround the generated code for the grammar element of interest (rule, alternate, token reference, or rule reference). If no http://stackoverflow.com/questions/18132078/handling-errors-in-antlr4 exception handlers (default or otherwise) are specified, then the exception will propagate all the way out of the parser to the calling program. ANTLR's default exception handling is good to get something working, but you will have more control over error-reporting and resynchronization if you write your own exception handlers. Note that the '@' exception specification of PCCTS 1.33 does not http://www.antlr2.org/doc/err.html apply to ANTLR. ANTLR Exception Hierarchy ANTLR-generated parsers throw exceptions to signal recognition errors or other stream problems. All exceptions derive from ANTLRException. The following diagram shows the hierarchy: Exception Description ANTLRException Root of the exception hiearchy. 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. CharStreamException Something bad that happens on the character input stream. Most of the time it will be an IO problem, but you could define an exception for input coming from a dialog box or whatever. CharStreamIOException The character input stream had an IO exception (e.g., CharBuffer.fill() can throw this). If nextToken() sees this, it will convert it to a TokenStreamIOException. RecognitionException A generic recognition problem with the input. Use this as your "catch all" exception in your main() or other method that invokes a parser, lexer, or treeparser. All parser rules throw this exception. MismatchedCharException Thrown by CharScanner.match() when it is looking for a character, but finds a different one on the input stream. MismatchedTokenException Thrown
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