[JEXL-321] Empty do-while loop is broken

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1
• Fix Version/s: 3.2
• Assignee: Unassigned
• Reporter: Dmitri Blinov
• Created: 17/Jan/20 12:13
• Updated: 07/Jun/21 13:14
• Resolved: 17/Jan/20 15:48

Description

The following test case with AIOOB.

    @Test
    public void testEmptyBody() throws Exception {
        JexlScript e = JEXL.createScript("var i = 0; do ; while((i+=1) < 10); i");
        JexlContext jc = new MapContext();
        Object o = e.execute(jc);
        Assert.assertEquals(10, o);       
    } 

The suggestion is to change interpreter as follows

    @Override
    protected Object visit(ASTDoWhileStatement node, Object data) {
        Object result = null;
        /* last objectNode is the expression */
        Node expressionNode = node.jjtGetChild(node.jjtGetNumChildren()-1);
        do {
            cancelCheck(node);
            if (node.jjtGetNumChildren() > 1) {
                try {
                    // execute statement
                    result = node.jjtGetChild(0).jjtAccept(this, data);
                } catch (JexlException.Break stmtBreak) {
                    break;
                } catch (JexlException.Continue stmtContinue) {
                    //continue;
                }
            }
        } while (arithmetic.toBoolean(expressionNode.jjtAccept(this, data)));
        return result;
    }

and Debugger as follows

    @Override
    protected Object visit(ASTDoWhileStatement node, Object data) {
        int num = node.jjtGetNumChildren();
        builder.append("do ");
        if (num > 1) {
            acceptStatement(node.jjtGetChild(0), data);
        } else {
            builder.append(" ; ");
        }
        builder.append(" while (");
        accept(node.jjtGetChild(num - 1), data);
        builder.append(")");
        return data;
    }