[jira] [Comment Edited] (JEXL-307) Variable redeclaration option

["Dmitri Blinov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JEXL-307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17020834#comment-17020834 ] 

Dmitri Blinov edited comment on JEXL-307 at 1/23/20 7:26 AM:
-------------------------------------------------------------

And one more thing... hoisted variables are not resolved in nested blocks - _*variable 'x' is undefined*_
{code:java}
    @Test
    public void testHoisted() throws Exception {
        JexlFeatures f = new JexlFeatures();
        f.lexical(true);
        JexlEngine jexl = new JexlBuilder().strict(true).features(f).create();
        JexlScript script = jexl.createScript("var x = 10; var a = function(var b) {for (var q : 1 ..10) {return x + b}}; a(32)");
        JexlContext jc = new MapContext();
        Object result = script.execute(null);
        Assert.assertEquals(result, 42);
    }
 {code}
If the lexical feature is switched off everything works OK.

The problem stems from the fact that hoisted variables *may* change their frame pointer index (aka symbol) between frames. So when we check identifier inside {{JexlParser.checkVariable()}} we can not simply check for all lexical units for the identifier to be declared by its *symbol*. We either need to keep track of Frame-LexicalUnit relation when we traverse the lexical stack, or to check for variable by identifier *name* inside LexicalUnit.


was (Author: dmitri_blinov):
And one more thing... hoisted variables are not resolved in nested blocks - _*variable 'x' is undefined*_
{code:java}
    @Test
    public void testHoisted() throws Exception {
        JexlFeatures f = new JexlFeatures();
        f.lexical(true);
        JexlEngine jexl = new JexlBuilder().strict(true).features(f).create();
        JexlScript script = jexl.createScript("var x = 10; var a = function(var b) {for (var q : 1 ..10) {return x + b}}; a(32)");
        JexlContext jc = new MapContext();
        Object result = script.execute(null);
        Assert.assertEquals(result, 42);
    }
 {code}
If the lexical feature is switched off everything works OK.

> Variable redeclaration option
> -----------------------------
>
>                 Key: JEXL-307
>                 URL: https://issues.apache.org/jira/browse/JEXL-307
>             Project: Commons JEXL
>          Issue Type: New Feature
>    Affects Versions: 3.1
>            Reporter: Dmitri Blinov
>            Assignee: Henri Biestro
>            Priority: Minor
>             Fix For: 3.2
>
>
> As of now, JEXL allows a script writer to redeclare a local variable during script evaluation.
> {code:java}
> var a = 1; var a = 2;{code}
> This may lead to potential errors with misspelled names and clashed variables. Checking for already defined variable is a common feature of many languages. This feature can be implemented in JEXL as an additional option of JexlFeatures class, enabled by default, thus allowing compatibility with existing code.



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