[jira] [Comment Edited] (FREEMARKER-60) Document interaction between lazy import and #global

["Daniel Dekany (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FREEMARKER-60?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16070390#comment-16070390 ] 

Daniel Dekany edited comment on FREEMARKER-60 at 6/30/17 4:54 PM:
------------------------------------------------------------------

Since the imported template is not executed at all until something accesses a namespace member (in fact, might not even loaded until that), it's not a special case. We can add some notices about that, but I think it's not a surprising behavior.

As of disqualifying templates based on what they do, the main problem there is that nothing can be told about the content of an imported template until it was actually loaded (or get from the cache), so if laziness depends on template content, then all lazy imports has to be loaded (even if not executed), which is of course makes laziness less useful. Even if you have the {{Template}}, it can't be reliably detected if something will create global variables, partly because of {{#include}} and {{?interpret}}, which are only resolved during execution. Also it's not entirely sure that not creating global variables is a problem before the imported namespace is used. Also imports can do other things with side effects, like create HTTP request attributes, call into other imports that might have a global effect, etc. So I think only explicit disqualification could work, where you specify in the {{Configuration}} that if the template's lookup name (not even the source name) matches certain pattern then it can't be lazy imported.




was (Author: ddekany):
Since the imported template is not executed at all until something accesses a namespace member, it's not a special case. We can add some notices about that, but I think it's not a surprising behavior.

As of disqualifying templates based on what they do, the main problem there is that nothing can be told about the content of an imported template until it was actually loaded (or get from the cache), so if laziness depends on template content, then all lazy imports has to be loaded (even if not executed), which is of course makes laziness less useful. Even if you have the {{Template}}, it can't be reliably detected if something will create global variables, partly because of {{#include}} and {{?interpret}}, which are only resolved during execution. Also it's not entirely sure that not creating global variables is a problem before the imported namespace is used. Also imports can do other things with side effects, like create HTTP request attributes, call into other imports that might have a global effect, etc. So I think only explicit disqualification could work, where you specify in the {{Configuration}} the templates lookup name (not even the source name) matches certain pattern can't be lazy imported.



> Document interaction between lazy import and #global
> ----------------------------------------------------
>
>                 Key: FREEMARKER-60
>                 URL: https://issues.apache.org/jira/browse/FREEMARKER-60
>             Project: Apache Freemarker
>          Issue Type: Improvement
>          Components: documentation
>    Affects Versions: 2.3.26-incubating
>            Reporter: Jasper Rosenberg
>            Priority: Trivial
>
> If I am understanding what is going on correctly, it appears that when you turn on lazy imports, #global variables defined in that file will not be defined unless something else first accesses the imported file's namespace.  This is a bit of a weird case so it might just be worth documenting.
> Alternatively, you could say that if you have #global variables defined in a file it disqualifies it from being lazily imported.



--
This message was sent by Atlassian JIRA
(v6.4.14#64029)