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https://issues.apache.org/jira/browse/JEXL-426?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Henri Biestro resolved JEXL-426.
--------------------------------
Resolution: Fixed
Commit
[e5f4f5f8|https://github.com/apache/commons-jexl/commit/e5f4f5f8934152d9b75c245ffe526867c951a89e]
> Enable pass-by-reference for Captured Variables
> ------------------------------------------------
>
> Key: JEXL-426
> URL: https://issues.apache.org/jira/browse/JEXL-426
> Project: Commons JEXL
> Issue Type: Improvement
> Affects Versions: 3.4.0
> Reporter: Xu Pengcheng
> Assignee: Henri Biestro
> Priority: Major
> Fix For: 3.5.0
>
>
> For the code
> {code:java}
> let x = 10;
> function foo() {
> x += 2;
> }
> foo();
> return x;{code}
> By default the return value of x is 10 because `x` inside `foo` is a captured
> value, re-assign value not affect the variable outside `foo`, which some
> times confuse the developer, therefore a new feature `constCapture` was
> introduced to prevent such kind of re-assignment, which is the same behavior
> of Java code.
> But the problem is variable `x` outside of function is not const, for the
> following code
>
> {code:java}
> 1: let x = 10;
> 2: function foo() {
> 3: someCall(x);
> 4: }
> 5: x = 20;
> 6: foo();
> 7: return x; {code}
> This code is valid with constCapture = true (similar code in java is invalid
> because x needs to be 'final'), but the value inside `foo` is 10, not 20, I
> checked the JEXL source codes and found the value inside `foo` is captured
> when defining `foo` function (line 3), which is 10, even when calling `foo`
> in line 6 the value of x is already be 20, this case is also somehow confuse.
>
> I tried extending Interpreter to change the behavior of captured variable to:
> # re-assign the captured variable to latest value from parent frame before
> executing.
> # populate the value to parent scope while assigning new value to a captured
> variable
> with this interpreter, the value of x in line 3 and 7 are 22, which I think
> is more easy to understand.
> {code:java}
> 1: let x = 10;
> 2: function foo() {
> 3: x += 2; // here x = 22
> 4: }
> 5: x = 20;
> 6: foo();
> 7: return x; // here x = 22{code}
>
> Is it possible to add a new feature to support this behavior?
> or provide more apis, i.e.
> # api to get whole frame stack (now I store it in JexlContext)
> # read/write value by variable name for a frame (now I reflect the
> get/set/getSymbol methods of Frame class)
> # get parent of Scope.
> Thanks very much!
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