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From "Jason Winnebeck (JIRA)" <>
Subject [jira] [Commented] (GROOVY-7956) Allow @DelegatesTo on named arguments
Date Tue, 04 Oct 2016 19:40:20 GMT


Jason Winnebeck commented on GROOVY-7956:

This is an awesome idea, although I'm not sure that reusing {{@DelegatesTo}} is the most clear
option... But whatever the annotation would be called, this would also be a great improvement
for any "options-like" API more common in the JavaScript/TypeScript world but we see it for
example with Groovy http-builder:

        path: 'update.json',
        body: [ status: msg, source: 'httpbuilder' ],
        requestContentType: URLENC )

In this case it would be nice if the path, body, and requestContentType were known to the
Groovy static compiler and IDEs. If there was a way to describe the structure (supporting
even nested objects), it would be nice. There would be some question whether or not there
should be a "prototype" type (as in the original proposal, like {{@Properties(Animal)}}) supported
in addition to a "descriptive" form purely in annotations that would be supported even for
dynamic mode (for example {{@Properties(\[x: Integer, y: Integer])}} for a method taking a
Map of x,y values).

> Allow @DelegatesTo on named arguments
> -------------------------------------
>                 Key: GROOVY-7956
>                 URL:
>             Project: Groovy
>          Issue Type: New Feature
>          Components: GEP
>            Reporter: Graeme Rocher
> In order to aid static compilation for builders we have {{@DelegatesTo}} which allows
statically compiled code to know what the delegate of a closure is.
> This proposal is to allow {{@DelegatesTo}} on {{Map}} types such that IDEs and the static
compiler can resolve the target type the named arguments are to be used on.
> For example:
> {code}
> class Farm {
>      void animal(@DelegatesTo(Animal) Map arguments, @DelegatesTo(AnimalBuilder) Closure
callable) {
>              def animal = new Animal(arguments)
>              // handle closure
>     }
> } 
> class Animal { String name }
> {code}
> The following code would then fail to compile :
> {code}
> def farm = new Farm()
> // compilation failure, no name property on Animal
> farm.animal(nam: "Dog")  { 
> }
> {code}
> It would then be down to IDEs to also provide support for code completion etc.

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