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https://issues.apache.org/jira/browse/GROOVY-12557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18135409#comment-18135409
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ASF GitHub Bot commented on GROOVY-12557:
-----------------------------------------
paulk-asert commented on PR #3085:
URL: https://github.com/apache/groovy/pull/3085#issuecomment-6533138247
Suggested test tweaks, fine as a follow-up after merge too:
> **1. Per-instance state instead of static counters.** The counter and the
failure switch can live on each `Watched`, which drops the `@BeforeEach` reset
and any shared state between tests:
>
> ```groovy
> static class Watched {
> int metaClassCalls
> boolean failMetaClass
>
> @Override
> MetaClass getMetaClass() {
> metaClassCalls++
> if (failMetaClass) {
> throw new IllegalStateException('getMetaClass() called')
> }
> InvokerHelper.getMetaClass(Watched)
> }
> }
>
> @Test
> void 'a cast of a value that has the target type does not call
getMetaClass'() {
> Watched first = new Watched()
> Watched second = new Watched()
>
> assertSame first, castToWatched(first)
> assertSame second, castToWatched(second)
> assertEquals 0, first.metaClassCalls
> assertEquals 0, second.metaClassCalls
> }
>
> @Test
> void 'a cast succeeds when getMetaClass of the value fails'() {
> Watched watched = new Watched(failMetaClass: true)
>
> assertSame watched, castToWatched(watched)
> }
> ```
>
> **2. A proxy-shaped case.** The reported failure is a class-based proxy,
which is a subclass of the target type. The current tests cast `Watched` to
exactly `Watched`. Both go through the same identity handle, but one extra test
pins the reported shape:
>
> ```groovy
> static class WatchedProxy extends Watched {
> @Override
> MetaClass getMetaClass() {
> throw new IllegalStateException('target out of scope')
> }
> }
>
> @Test
> void 'a cast of a subclass proxy whose getMetaClass fails succeeds'() {
> WatchedProxy proxy = new WatchedProxy()
>
> assertSame proxy, castToWatched(proxy)
> }
> ```
> Indy: casting a GroovyObject calls getMetaClass() on the value being cast
> -------------------------------------------------------------------------
>
> Key: GROOVY-12557
> URL: https://issues.apache.org/jira/browse/GROOVY-12557
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.1.3, 6.0.0
> Reporter: James Daugherty
> Priority: Major
>
> With invokedynamic, a cast of a {{GroovyObject}} that already has the target
> type, such as {{Widget widget = value}}, calls {{value.getMetaClass()}}: once
> to build the call site's guard and again on each call through it. With
> classic call sites the same cast calls nothing on the value.
> That is observable whenever {{getMetaClass()}} is not a plain field read. A
> Spring class-based (CGLIB) proxy of a Groovy class forwards every public
> method, {{getMetaClass()}} included, to its target. For a step-, job-,
> request- or session-scoped bean the target exists only while the scope is
> active, so merely assigning the proxy to a typed variable outside the scope
> fails:
> {noformat}
> org.springframework.beans.factory.support.ScopeNotActiveException: Error
> creating bean with name 'scopedTarget.widget': Scope 'step' is not active for
> the current thread
> at
> org.springframework.aop.target.SimpleBeanTargetSource.getTarget(SimpleBeanTargetSource.java:35)
> at
> org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:698)
> at Widget$$SpringCGLIB$$0.getMetaClass
> at org.codehaus.groovy.vmplugin.v8.Selector$MethodSelector.setGuards
> at org.codehaus.groovy.vmplugin.v8.Selector$CastSelector.castAndSetGuards
> at org.codehaus.groovy.vmplugin.v8.Selector$CastSelector.setCallSiteTarget
> at org.codehaus.groovy.vmplugin.v8.IndyInterface.fallback
> {noformat}
> A Grails application moving from classic call sites to invokedynamic (the
> Grails 9 default) meets this in code that handles scoped proxies dynamically.
> *Reproducer:*
> https://github.com/jdaugherty/groovy-indy-cast-getmetaclass-reproducer
> ({{./run.sh 4.0.33 5.1.3 6.0.0}}). With indy the cast {{Watched typed =
> value}} makes 2 {{getMetaClass()}} calls on the value and fails when
> {{getMetaClass()}} throws; with classic call sites it makes none. Reproduced
> on 4.0.33, 5.1.3 and 6.0.0.
> *Cause:* {{Selector.CastSelector.castAndSetGuards()}} reuses
> {{MethodSelector.setGuards(args[0])}}, which calls {{getMetaClass()}} on a
> {{GroovyObject}} receiver to bind a {{SAME_MC}} guard. Only a cast to boolean
> selects a method ({{asBoolean}}) through the metaclass; every other cast is
> decided by the class of the value, which the argument guards and the class
> SwitchPoint already cover.
> *Proposed fix:* keep the receiver metaclass guard for the {{asBoolean}} path
> only, so a cast decided by the value's class never calls into the value, as
> with classic call sites. A patch with tests follows as a pull request against
> master, with backports for the 6.0.x and 5.1.x lines.
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