CssSelectors contexts are not computed in CssParseException

[AdrianSorop]

Here is a quick JUnit test to reproduce the issue:

public void testPresentContextInErrors() throws Exception {
    
    String css = 
        "    td\n" + 
        "    {\n" + 
        "        color:something;\n" + 
        "    }";
    URL url = new URL("file://fake.css");
    Reader reader = new StringReader(css);
    ApplContext applContext = new ApplContext("en");
    applContext.setCssVersion("css3");
    applContext.setProfile("css3");
    applContext.setMedium("all");
    applContext.setWarningLevel(2);
    StyleSheetParser sheetParser = new StyleSheetParser(applContext);

    sheetParser.parseStyleElement(applContext, reader, null, applContext.getMedium(), url, 0);
    sheetParser.getStyleSheet().findConflicts(applContext);

    Errors errors = sheetParser.getStyleSheet().getErrors();
    assertEquals("“something” is not a “color” value", errors.getErrorAt(0).getException().getMessage());
    CssError error = errors.getErrorAt(0);
    CssParseException exception = (CssParseException) error.getException();
    
    StringBuilder messageBuilder = new StringBuilder();
    ArrayList<CssSelectors> contexts = exception.getContexts();
    if (contexts != null && !contexts.isEmpty()) {
      StringBuffer buf = new StringBuffer();
      for (Iterator<CssSelectors> iterator = contexts.iterator(); iterator.hasNext();) {
        CssSelectors selector = iterator.next();
        buf.append(selector);
        if (iterator.hasNext()) {
          buf.append(", ");
        }
      }
      if (buf.length() != 0) {
        messageBuilder.append("Context: ").append(buf).append(' ');
      }
    }
    if (exception.getProperty() != null) {
      messageBuilder.append("in property: ").append(exception.getProperty());
    }
    
    assertEquals("Context: td in property: color", messageBuilder.toString());
  }

I managed to fix this in the org.w3c.css.parser.analyzer.CssParser.ruleSet() method by moving the assigment of currentContext = context_set; after the context_set was computed: context_set = selector_list()
Here the code that worked for me:

/**
 * @exception ParseException exception during the parse
 */
void ruleSet() :
{ 
    ArrayList<CssSelectors> context_set = null;
    ArrayList<CssProperty> value_set = null;
    /////////////// PATCH START //////////////
    //  Commented, has no effect here; moved after the context_set is computed.
	//	currentContext = context_set;
	/////////////// PATCH END //////////////
}
{
    try {
	context_set = selector_list()

	/////////////// PATCH START //////////////
	{
	    currentContext = context_set;
	}
	///////////////PATCH END //////////////
......

[ylafon]

Thanks for the report, I modified slightly the proposed fix to make it only happen if the selector list is not empty, but good catch, it will make reporting far more accurate and useful.