[jira] [Commented] (JEXL-390) Pragmas should not be statements

["Henri Biestro (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JEXL-390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17648692#comment-17648692 ] 

Henri Biestro commented on JEXL-390:
------------------------------------

I agree, #pragma should *not* be statements; it is confusing and misleading.
I'm partial on their placement; declaring a pragma close to its point of use (jexl.namespace in particular) is often convenient.
I'll try and submit a proposal momentarily.

> Pragmas should not be statements
> --------------------------------
>
>                 Key: JEXL-390
>                 URL: https://issues.apache.org/jira/browse/JEXL-390
>             Project: Commons JEXL
>          Issue Type: Improvement
>    Affects Versions: 3.2.1
>            Reporter: Dmitri Blinov
>            Assignee: Henri Biestro
>            Priority: Minor
>             Fix For: 3.3
>
>
> In Jexl pragmas are treated as statements syntactically, but do not find their way to AST tree and this leads to strange bugs like in the following example
> {code}
>     @Test
>     public void testBadPragmas() throws Exception {
>         final JexlEngine jexl = new JexlBuilder().cache(1024).debug(true).create();
>         final JexlScript script = jexl.createScript("if (true) #pragma one 42");
>         JexlContext jc = new MapContext();
>         final Object result = script.execute(jc);
>         debuggerCheck(jexl);      
>     }
> {code}
> While this partucular bug can be trivially fixed, in fact the whole idea to allow putting pragmas for example inside a loop or inside if-branch is a strange language design (I'm not aware of examples in other languages) as it gives false idea of the pragma being controlled by script execution logic. 
> If there's no reason or use case to keep this design as is, my proposal is to make a grammar change and allow pragmas to be declared only at the top of the script. Another point to change current pragma implementation is that pragmas can not be used with expressions, e.g. no way to specify standard options / imports.  



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