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From "Jochen Theodorou (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (GROOVY-8952) Eager interpolation evaluating as a Closure does a lazy invoke of the Closure
Date Wed, 09 Jan 2019 08:13:00 GMT

    [ https://issues.apache.org/jira/browse/GROOVY-8952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16737960#comment-16737960
] 

Jochen Theodorou commented on GROOVY-8952:
------------------------------------------

To some extend [http://docs.groovy-lang.org/docs/next/html/documentation/#_closures_in_gstrings]
explains it. Instead of me repeating and explaining in other words, what is written there
it would be nice if you could explain what exactly you are missing there. Of course I realize
that this paragraph is very short and probably lacks an important aspect, but for us it is
difficult to realize what essential information is missing there. Blindness due to knowledge
so to say.

> Eager interpolation evaluating as a Closure does a lazy invoke of the Closure
> -----------------------------------------------------------------------------
>
>                 Key: GROOVY-8952
>                 URL: https://issues.apache.org/jira/browse/GROOVY-8952
>             Project: Groovy
>          Issue Type: Bug
>    Affects Versions: 2.5.5
>         Environment: Windows 10
>            Reporter: Chaitanya Birudavolu
>            Priority: Major
>              Labels: closure, eager, interpolation
>
> This is regarding the eager interpolation placeholder
> {code:java}
> ${ <expression> }{code}
> The expected behavior is that the expression would be evaluated eagerly (at GString
creation time). Later, at GString coercion time, the value that is expected in the place
of the eager placeholder is the result of
> {code:java}
> <expression>.toString(){code}
>  
>  
> This works most of the time, but doesn't seem to work if the expression evaluates to
a Closure type. If the expression evaluates to a Closure type, what is observed is that, in
the place of the placeholder, instead of seeing ...
> {code:java}
> <closure>.toString(){code}
> ... we see...
> {code:java}
> <closure-invocation-result>.toString(){code}
> For example, in the below code...
>  
> {code:java}
> def c = {->println ('Inside closure')}
> println ('Just before creating the GString')
> def gstr = "${println ('Inside eager placeholder'); 20; 30; c}"
> println ('Just after creating the GString')
> println (gstr)
> {code}
>  
> ...the expected behavior is that the closure should never get executed, and the last
println should only print the result of
> {code:java}
> c.toString(){code}
> Instead, the last line printed is observed to be:
> {code:java}
> Inside closure{code}
>  



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