Dmitri Blinov created JEXL-256:
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             Summary: Jexl should not try to resolve a variable from Context 
when Context.has() returns false
                 Key: JEXL-256
                 URL: https://issues.apache.org/jira/browse/JEXL-256
             Project: Commons JEXL
          Issue Type: Improvement
    Affects Versions: 3.1
            Reporter: Dmitri Blinov


I have bumped into the problem when my {{Context.get()}} sometimes reports 
access to variables that are reported by the {{Context.has()}} method as not 
existent, and are not supposed to be in the context, mainly parts of ant-ish 
variable paths. I assume that once {{Context.has()}} have reported {{false}} no 
attempt from the Jexl to call {{Context.get()}} with the same parameter should 
be made.

I think the problem lies in {{Interpreter.java}} which first calls 
{{Context.get()}} and only if it returns null, which should not necceserily 
mean the variable does not exist, checks {{Context.get()}}. 

{code}
    @Override
    protected Object visit(ASTIdentifier node, Object data) {
        cancelCheck(node);
        String name = node.getName();
        if (data == null) {
            int symbol = node.getSymbol();
            if (symbol >= 0) {
                return frame.get(symbol);
            }
            Object value = context.get(name);
            if (value == null
                    && !(node.jjtGetParent() instanceof ASTReference)
                    && !context.has(name)
                    && !node.isTernaryProtected()) {
                return unsolvableVariable(node, name, true);
            }
            return value;
        } else {
            return getAttribute(data, name, node);
        }
    }
{code}

So I suggest to change the code to something like this

{code}
    @Override
    protected Object visit(ASTIdentifier node, Object data) {
        cancelCheck(node);
        String name = node.getName();
        if (data == null) {
            int symbol = node.getSymbol();
            if (symbol >= 0) {
                return frame.get(symbol);
            }
            if (!context.has(name)
                    && !(node.jjtGetParent() instanceof ASTReference)
                    && !node.isTernaryProtected()) {
                return unsolvableVariable(node, name, true);
            }
            return context.get(name);
        } else {
            return getAttribute(data, name, node);
        }
    }
{code}




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