[antlr-interest] Stopping parser and lexer at first error

[Corrado Campisano]

Hi all,

I setup an ANTLR-maven archetype with a grammar providing the override for
the 'always resume' behaviour.

You can find details on my
website<http://www.servicemix.eu/index.php?option=com_content&view=article&id=14>,
maybe it's worth checking it and adding a notice on this archetype to this
ANTLR wiki page<http://www.antlr.org/wiki/display/ANTLR3/Building+ANTLR+Projects+with+Maven>and/or
to the ANTLR
v3 Maven plugin page <http://www.antlr.org/antlr3-maven-plugin/index.html>.


Regards,
Corrado.


2010/3/10 Corrado Campisano <corrado.campisano at gmail.com>

> Hi all,
>
> I needed to catch any syntax error (letting the lexer insert/delete chars
> or the parser keeping parsing with the sys.err message only could be very
> dangerous to my application), so I took a look on the reference (which
> reports information not valid anymore) and on the internet and I found
> several hints and articles:
>
> Why the generated parser code tolerates illegal expression?<http://www.antlr.org/wiki/pages/viewpage.action?pageId=4554943>
> How can I make the lexer exit upon first lexical error?<http://www.antlr.org/wiki/pages/viewpage.action?pageId=5341217>
> http://www.antlr.org/wiki/display/ANTLR3/Custom+Syntax+Error+Recovery
> [antlr-interest] I want to throw an exception and stop parse, please!
> <http://www.antlr.org/pipermail/antlr-interest/2009-May/034605.html>
>
> It looks to me I found a way to do this, maybe it's worth to publish that
> on the wiki, once validated.
>
>
> I just added the following overrides to my grammar (attached):
>
> @parser::members
> {
>     public class ParserException extends RuntimeException {
>             Object objCurrentInputSymbol = null;
>
>             public ParserException(Object oCurrentInputSymbol) {
>                 this.objCurrentInputSymbol = oCurrentInputSymbol;
>             }
>         }
>
>         protected Object recoverFromMismatchedToken(IntStream input, int
> ttype, BitSet follow) throws RecognitionException {
>             System.out.println("PARSER :
> this.getCurrentInputSymbol(input).toString() : " +
> this.getCurrentInputSymbol(input).toString());
>             System.out.println("PARSER : this.failed() : " +
> this.failed());
>             System.out.println("PARSER : this.getNumberOfSyntaxErrors() : "
> + this.getNumberOfSyntaxErrors());
>             throw new ParserException(this.getCurrentInputSymbol(input));
>         }
> }
>
> @lexer::members
> {
>     public class LexerException extends RuntimeException {
>             RecognitionException recognitionException = null;
>             String strErrorHeader = null;
>             String strErrorMessage = null;
>
>             public LexerException(RecognitionException recExc, String
> sHead, String sMsg) {
>                 this.recognitionException = recExc;
>                 this.strErrorHeader = sHead;
>                 this.strErrorMessage = sMsg;
>
>                 System.out.println("LEXER : ErrorHeader : " + sHead);
>                 System.out.println("LEXER : ErrorMessage : " + sMsg);
>                 System.out.println("LEXER : RecognitionException : " +
> this.recognitionException.toString());
>             }
>         }
>
>
>         public void reportError(RecognitionException recExc) {
>         throw new LexerException(recExc, this.getErrorHeader(recExc),
> getErrorMessage(recExc, this.getTokenNames()));
>     }
> }
>
>
> Then I tested it with a simple class:
>     public static void main(String[] args) {
>         testLexerError();
>         testParserError();
>     }
>     private static void testLexerError() {
>         String strDlToParse = "{CORRADO PIPPO ;feee}";
>         System.out.println("TESTING LEXER with : " + strDlToParse);
>         testError(strDlToParse);
>     }
>     private static void testParserError() {
>         String strDlToParse = "{CORRADO PIPPO feee} dhert";
>         System.out.println("TESTING PARSER with : " + strDlToParse);
>         testError(strDlToParse);
>     }
>     private static void testError(String strDlToParse) {
>         CommonTree tree=null;
>         String strError = null;
>
>         ANTLRStringStream input = new
> org.antlr.runtime.ANTLRStringStream(strDlToParse);
>         Dl2OwlJavaBLexer lexer = new Dl2OwlJavaBLexer(input);
>         TokenStream tokens = new
> org.antlr.runtime.CommonTokenStream(lexer);
>         Dl2OwlJavaBParser parser = new Dl2OwlJavaBParser(tokens);
>
>         try {
>             // this may rise an exception
>             // TODO : check why NO EXCEPTION is risen with error "line 1:9
> no viable alternative at character ';'" on inputs like "{CORRADO ;}"
>             eu.servicemix.dl2owl.Dl2OwlJavaBParser.axiom_return ret =
> parser.axiom();
>
>             // TODO : check if this will be executed if no exception rises
>             tree = (CommonTree) ret.getTree();
>
>             printTreeHelper(tree);
>
>         } catch (RecognitionException e) {
>
>             System.out.println(e.toString());
>             e.printStackTrace();
>
>         } catch (RuntimeException e) {
>
>             System.out.println(e.toString());
>             e.printStackTrace();
>         }
>     }
>
>
> The output looks ok, I wonder whether the whole 'trick' is too...
>
> TESTING LEXER with : {CORRADO PIPPO *;*feee}
> LEXER : ErrorHeader : line 1:15
> LEXER : ErrorMessage : no viable alternative at character ';'
> LEXER : RecognitionException : NoViableAltException(';'@[1:1: Tokens : (
> T__37 | T__38 | T__39 | T__40 | HAS_VALUE | ALL_VALUES | SOME_VALUES | DOT |
> HAS_CARD | MIN_CARD | MAX_CARD | NOT | AND | OR | URI_REF | INT_VALUE | WS |
> CTRL_CHAR );])
> eu.servicemix.dl2owl.Dl2OwlJavaBLexer$LexerException
> eu.servicemix.dl2owl.Dl2OwlJavaBLexer$LexerException
>     at
> eu.servicemix.dl2owl.Dl2OwlJavaBLexer.reportError(Dl2OwlJavaBLexer.java:69)
>     at org.antlr.runtime.Lexer.nextToken(Lexer.java:94)
>     at
> org.antlr.runtime.CommonTokenStream.fillBuffer(CommonTokenStream.java:119)
>     at org.antlr.runtime.CommonTokenStream.LT<http://org.antlr.runtime.commontokenstream.lt/>
> (CommonTokenStream.java:238)
>     at
> eu.servicemix.dl2owl.Dl2OwlJavaBParser.axiom(Dl2OwlJavaBParser.java:110)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.testError(CommonTreeHelper.java:140)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.testLexerError(CommonTreeHelper.java:121)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.main(CommonTreeHelper.java:113)
>
> TESTING PARSER with : {CORRADO PIPPO feee} *dhert*
> PARSER : this.getCurrentInputSymbol(input).toString() :
> [@8,21:25='dhert',<7>,1:21]
> PARSER : this.failed() : false
> PARSER : this.getNumberOfSyntaxErrors() : 0
> eu.servicemix.dl2owl.Dl2OwlJavaBParser$ParserException
> eu.servicemix.dl2owl.Dl2OwlJavaBParser$ParserException
>     at
> eu.servicemix.dl2owl.Dl2OwlJavaBParser.recoverFromMismatchedToken(Dl2OwlJavaBParser.java:97)
>     at org.antlr.runtime.BaseRecognizer.match(BaseRecognizer.java:115)
>     at
> eu.servicemix.dl2owl.Dl2OwlJavaBParser.axiom(Dl2OwlJavaBParser.java:232)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.testError(CommonTreeHelper.java:140)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.testParserError(CommonTreeHelper.java:126)
>     at
> eu.servicemix.dl2owl.CommonTreeHelper.main(CommonTreeHelper.java:114)
>
>
> Any comment really appreciated!!
>
> Corrado
>
>