Pattern for returning errors from ANTLR in data structures, not STDERR

Owned by TerenceP
Last updated: Dec 01, 2010Version comment
1 min read

My ANTLR parser is embedded in other code. I've decided that reporting errors out of the parser would be better handled as a list of errors instead of having them sent to stderr.

In the v4 prerelease stuff, there is an example. Tool.java has

Tool.java

	public void error(Message msg) {
		if ( listeners.size()==0 ) {
			defaultListener.error(msg);
			return;
		}
		for (ANTLRToolListener l : listeners) l.error(msg);
	}

using ANTLRToolListener.java then in ToolANTLRParser.java I do:

	public void displayRecognitionError(String[] tokenNames,
										RecognitionException e)
	{
		String msg = getParserErrorMessage(this, e);
		if ( paraphrases.size()>0 ) {
			String paraphrase = (String)paraphrases.peek();
			msg = msg+" while "+paraphrase;
		}
	//	List stack = getRuleInvocationStack(e, this.getClass().getName());
	//	msg += ", rule stack = "+stack;
		tool.errMgr.syntaxError(ErrorType.SYNTAX_ERROR, getSourceName(), e.token, e, msg);
	}

which forces all msgs from antlr to shunt to Tool.error(), which announces to listeners.

For testing, i have unit tests use this ErrorQueue.java as a listener to the tool like so:

			Tool antlr = newTool(optionsA);
			antlr.addListener(equeue);