[jira] [Commented] (GROOVY-11118) Partial JEP 445 compatibility

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-11118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17739776#comment-17739776 ] 

ASF GitHub Bot commented on GROOVY-11118:
-----------------------------------------

paulk-asert opened a new pull request, #1910:
URL: https://github.com/apache/groovy/pull/1910

   (no comment)




> Partial JEP 445 compatibility
> -----------------------------
>
>                 Key: GROOVY-11118
>                 URL: https://issues.apache.org/jira/browse/GROOVY-11118
>             Project: Groovy
>          Issue Type: New Feature
>            Reporter: Paul King
>            Assignee: Paul King
>            Priority: Major
>              Labels: GEP, breaking
>             Fix For: 5.x
>
>
> [JEP 445: Unnamed Classes and Instance Main Methods|https://openjdk.org/jeps/445] provides features that improve using Java for scripting purposes. While these features offer a subset of the features offered by Groovy for scripting, it would be nice to offer some interworking for cut-n-paste compatibility and leveraging the updated launch protocol.
> (i) This description will contain the most update-to-date proposal for the design but may undergo change during discussions. If needed, a separate GEP section in the wiki will capture the final design.
> h2. Scripting semantics
> ||Source file characteristics||Semantics determined||
> |Contains class declaration|Compiled as a class|
> |Contains uncontained non-declaration statements
> or a static main method|Compiled as a Groovy script|
> |Contains an instance main method, and
> possibly field and other method declarations|Compiled as a JEP 445 compatible class|
> Groovy scripts are wrapped into an encompassing class that extends {{{}groovy.lang.Script{}}}.
> Such classes have a {{public static void main}} added which (summarising) creates a class instance and calls its {{run}} method.
> Uncontained statements within the script can be thought of as belonging within the {{run}} method.
> Declaration statements within the script are treated as local variable definitions (also within the {{run}} method).
> Field definitions can be obtained by annotating declaration statements with the {{@Field}} annotation.
> JEP 445 scripts do not extend {{Script}} and do not have any methods added.
> Declaration statements within the script are treated as field definitions.
> h2. Script runner
> Groovy's runner mechanism will be extended to follow a similar protocol to Java's revised launch protocol. This should be available for JDK11+ and a JEP-445 compatible class could be invoked using JDK21+ with preview enabled (with Groovy on the classpath unless a POJO class is created).
> h2. Breaking changes
> Previously, if a script had a single instance {{main}} method not taking a {{String[]}} parameter and no loose statements, that was previously accepted as a normal Groovy script (and nothing would execute). Now if the method has an Object parameter, that is treated as a JEP-445 script and its contents executed.



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