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https://issues.apache.org/jira/browse/JEXL-237?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16087272#comment-16087272
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Henri Biestro commented on JEXL-237:
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The only case of potential problem we can detect (and preclude) at parsing time
is assigning a global variable.
Detecting whether local variables (i.e. those defined by the 'var' keyword)
clash in name with global (i.e. undeclared, determined at runtime) would
suggest creating/parsing scripts with a 'prototype' of their evaluation context
that would contain these expected global variables (and their potential sets of
types so we could perform type inference and further static method & operators
checks, sweet...).
This can also be implemented as a specific execution pass on a script just
after creation; extracting locals 'JexlScript.getVariables(...)'and check
though 'JexlContext.has(...)' whether any clashes and throw an ex in that case.
Seems to me the first step forward would certainly be able to parse with a 'no
assignment to global variable' set (which is related to the no-side-effect
expression task).
> Ability to restrict usage of certain names when declaring local variables
> -------------------------------------------------------------------------
>
> Key: JEXL-237
> URL: https://issues.apache.org/jira/browse/JEXL-237
> Project: Commons JEXL
> Issue Type: Wish
> Affects Versions: 3.1
> Reporter: Dmitri Blinov
> Priority: Minor
>
> One of the errors the scriptwriter usually makes is an accidental override of
> certain context variables with his own local variables, which leads to nasty
> bugs detected only when script is executed. As of now there is only a small
> list of reserved words that can not be used as a valid variable name, and it
> is restricted to basic Jexl syntax keywords. When Jexl syntax is extended
> with custom functions and predefined context variables, its much easier for a
> local variable name to clash with predefined name, thus altering script
> execution further on. To exclude those errors it is needed that a custom name
> verification would exist, prohibiting the scripts from be successfully parsed.
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