[jira] [Commented] (GROOVY-10192) Smarter Closure delegation detection in annotation parameters

["Eric Milles (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-10192?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17562763#comment-17562763 ] 

Eric Milles commented on GROOVY-10192:
--------------------------------------

Eclipse provides [DSLD|https://github.com/groovy/groovy-eclipse/wiki/DSL-Descriptors] and IntelliJ provides [GDSL|https://confluence.jetbrains.com/display/GRVY/Scripting+IDE+for+DSL+awareness] to describe delegation semantics and more.

Any change to allow {{@ClosureParams}} or {{@DelegatesTo}} in new positions would require IDE changes to support for purposes of content assist, syntax highlighting, etc.

> Smarter Closure delegation detection in annotation parameters
> -------------------------------------------------------------
>
>                 Key: GROOVY-10192
>                 URL: https://issues.apache.org/jira/browse/GROOVY-10192
>             Project: Groovy
>          Issue Type: Improvement
>          Components: Compiler
>    Affects Versions: 3.0.8, 4.0.0-alpha-3
>            Reporter: Marcin Zajaczkowski
>            Priority: Minor
>              Labels: annotations
>
> TL;TR. I would like to have a way to inform IDE that a passed in an annotation Closure's execution is in fact delegated to a specific object (type). E.g. "@Requires(\{ jvm.java11 })" should allow to write "jv" and see jvm in IDE (once a delegate has that field/getter).
> More detailed version (based on my question on the mailing list in [January 2020|https://mail-archives.apache.org/mod_mbox/groovy-users/202001.mbox/%3cb62eefce-5d71-f394-8024-f2dd93c12c04@wp.pl%3e]).
> One of the nice features of Spock is an ability to define conditions in Closure when test(s) should (not) be executes with @Required/@IgnoreIf.
>  
> {code:java}
>  @Requires({ isSpecialConditionFulfilled() })
>  def "some test"() {}
> {code}
> The annotation itself is defined as:
>  
> {code:java}
>  @Retention(RetentionPolicy.RUNTIME)
>  @Target({ElementType.TYPE, ElementType.METHOD})
>  @ExtensionAnnotation(RequiresExtension.class)
>  public @interface Requires {
>      Class<? extends Closure> value();
>  }
> {code}
> Down the line the execution is delegated to PreconditionContext which
>  provides convenient methods/objects such as os.linux, jvm.java11, env, etc.
> {code:java}
> @Requires({ jvm.java11 && os.linux }) {code}
> Unfortunately, there is no code completion as IDE doesn't know about
>  that delegation (and jvm, os fields/methods). Groovy 2 introduced
>  @DelegatesTo, however it cannot be used with other annotations or methods.
> It can be tricked by creating a static final instance of PreconditionContext (it's stateless) somewhere (e.g. in the Specification super class), but people has to know to refer it, e.g:
> {code:java}
> @Requires({ CTX.jvm.java11 }){code}
> Alternatively, I was thinking about a method in the base Spock class:
> {code:java}
>  protected static def ctx(@DelegatesTo(PreconditionContext) Closure closure) {
>      closure()
>  }{code}
> which could be referenced as:
> {code:java}
> @Requires({ ctx { jvm.java10Compatible } }){code}
> It works, but again "ctx" has to be referenced on demand.
> The best long-term solution would be to allow to use @DelegatesTo at the method level:
> {code:java}
> public @interface MyRequires { 
>     @DelegatesTo(PreconditionContext.class) Class<? extends Closure> value(); 
> } {code}
> It would provide code completion out of the box (once IDEs have support for that ). The second main drawback I see is being not very intuitive declaration and limited usage.



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