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From "Paul King (JIRA)" <>
Subject [jira] [Commented] (GROOVY-8952) Eager interpolation evaluating as a Closure does a lazy invoke of the Closure
Date Tue, 08 Jan 2019 11:33:00 GMT


Paul King commented on GROOVY-8952:

The code has always (well, at least since 2007) handled closures specially to allow lazy processing
in those rare cases when it does make sense:

I am unsure whether the above is your real use case or a cut down version. If we understood
what you were really trying to do, perhaps we could suggest some alternatives for you.

> Eager interpolation evaluating as a Closure does a lazy invoke of the Closure
> -----------------------------------------------------------------------------
>                 Key: GROOVY-8952
>                 URL:
>             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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