[
https://issues.apache.org/jira/browse/GROOVY-11508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17892647#comment-17892647
]
James Daugherty commented on GROOVY-11508:
------------------------------------------
I realized I didn't extend Parent, here's the full example. This works on
groovy 3.x, but not on 4.x:
{code:java}
import groovy.transform.CompileStatic
import java.util.Map
import java.util.List
class DatastoreHolder {
static Map<String, List> datastore = [:].withDefault { [] }
}
trait GormEntity<D> {
abstract static String getEntityName()
static List<D> getAll() {
DatastoreHolder.datastore.get(getEntityName())
}
}
class Parent implements GormEntity<Parent> {
String name
Parent() {
DatastoreHolder.datastore.get("Parent").add(this)
}
static String getEntityName() {
"Parent"
}
}
class Child extends Parent implements GormEntity<Child> {
String otherField
Child() {
super()
DatastoreHolder.datastore.get("Child").add(this)
}
static String getEntityName() {
"Child"
}
}
Parent p = new Parent()
Child c = new Child()
boolean expected = true
if( Parent.getAll().size() != 2) {
expected = false
System.out.println("Parent not expected: ${Parent.getAll()}")
}
if(Child.getAll().size() != 1) {
expected = false
System.out.println("Child not expected: ${Child.getAll()[0]} vs ${c}")
}
if(expected) {
System.out.println("Expected")
}{code}
> Multiple traits with related generic types cannot be used
> ---------------------------------------------------------
>
> Key: GROOVY-11508
> URL: https://issues.apache.org/jira/browse/GROOVY-11508
> Project: Groovy
> Issue Type: Bug
> Components: Compiler
> Affects Versions: 4.0.0
> Reporter: James Daugherty
> Assignee: Eric Milles
> Priority: Major
>
> When updating Grails from Groovy 3.x to 4.x we discovered that GROOVY-5106
> prevents us from updating to Groovy 4 for the
> [grails-data-mapping|https://github.com/grails/grails-data-mapping] (GORM)
> project. Groovy-5106 does not take into account relationships between
> generic types and groovy does not support inheritance in generic types on
> traits so we have no workable solution for using Groovy 4.
>
> For example, the following is not possible in Groovy 4:
> {code:java}
> class Parent extends GormEntity<Parent> {
> }
> class Child extends GormEntity<Child> {
> }
> class GormEntity<? extends GormEntity> { // ? extends GormEntity is not
> allowed
> }{code}
>
> We have documented the impacts of this issue on the grails-data-mapping
> project here: [https://github.com/grails/grails-data-mapping/issues/1811]
> We have discovered that the original change could be reverted and continue to
> work with the latest Java & Groovy.
>
> For Grails Data Mapping (GORM), there is support for inheritance between a
> Parent & Child domain object. This is often implemented like this:
> {code:java}
> class Parent extends GormEntity<Parent> {
> }
> class Child extends GormEntity<Child> {
> }
> trait GormEntity<D> { // Simplified for this ticket
> static D get(Serializable id)
>
> static List<D> getAll()
> }
> {code}
> This allows someone to do the following in code:
> {code:java}
> Parent.get(1L) // Will find either a Child or Parent
> Child.get(1L) // Will find only child types{code}
>
> Since Groovy-5106 does not take into account inheritance, can this change be
> reverted or changed to a warning until inheritance is taken into account?
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
