ANTLR not throwing errors on invalid input

Question

I\'m using ANTLR to parse logical expressions in a Java tool I\'m writing, and I\'m having issues because passing invalid input strings to the generated ANTLR lexer and pars

Answer 1

An easy fix would be to override your lexer's and parser's reportError(...) and throw an exception of your own instead of letting ANTLR trying to recover from the incorrect syntax/input:

grammar YourGrammar;

// options/header/tokens

@parser::members {
  @Override
  public void reportError(RecognitionException e) {
    throw new RuntimeException("I quit!\n" + e.getMessage()); 
  }
}

@lexer::members {
  @Override
  public void reportError(RecognitionException e) {
    throw new RuntimeException("I quit!\n" + e.getMessage()); 
  }
}

// lexer & parser rules

More on error reporting (and recovery): https://theantlrguy.atlassian.net/wiki/display/ANTLR3/Error+reporting+and+recovery

Answer 2

You should use an error listener as suggested in this answer

However, for a quick migration from antlr3 to antlr4 / antlr v4, you could use this as your grammer:

@parser::members 
{
  private final Logger log = LogManager.getLogger(this.getClass().getName());
  public java.util.HashMap<String, Double> memory = new java.util.HashMap<String, Double>();

  @Override
  public void notifyErrorListeners(Token offendingToken, String msg, RecognitionException ex)
  {
    throw new RuntimeException(msg); 
  }
}

@lexer::members 
{
  @Override
  public void recover(RecognitionException ex) 
  {
    throw new RuntimeException(ex.getMessage()); 
  }
}