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https://issues.apache.org/jira/browse/GROOVY-12578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18134528#comment-18134528
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ASF GitHub Bot commented on GROOVY-12578:
-----------------------------------------
codeconsole opened a new pull request, #3104:
URL: https://github.com/apache/groovy/pull/3104
When a closure body calls a method the closure inherits, such as
`toString()` or `with`, `tap` or `identity`, and neither the delegate nor the
owner can take it, the closure's own method now runs once and its result is
returned. This happens, for example, with `OWNER_ONLY` after `rehydrate(null,
null, null)`, or with `DELEGATE_ONLY` and no delegate.
`ClosureMetaClass` invoked that fallback, discarded the result and threw
`MissingMethodException`. Called from compiled code, invokedynamic caught the
exception and called the method again through `GroovyObject.invokeMethod`, so
`{ -> int n = 0; with { n++ }; n }` gave 2 there. Called through the meta class
directly, the call threw `MissingMethodException` after running the method.
Tests:
`ClosureDelegationTest.testClosureMethodWhenNeitherDelegateNorOwnerHasIt`,
which fails without the change. The `groovy`, `gls`, `bugs` and
`org.codehaus.groovy` packages pass (15,496 tests). The Checkstyle and CodeNarc
gates pass.
A regression in 6.0.0: 4.0.33 and 5.0.8 give 1.
> A closure's own method runs twice when neither the delegate nor the owner can
> take the call
> -------------------------------------------------------------------------------------------
>
> Key: GROOVY-12578
> URL: https://issues.apache.org/jira/browse/GROOVY-12578
> Project: Groovy
> Issue Type: Bug
> Components: groovy-runtime
> Affects Versions: 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> For an implicit-this call in a closure body to a method the closure inherits,
> such as {{toString()}} or a default Groovy method like {{with}}, {{tap}} or
> {{identity}}, {{ClosureMetaClass}} tries the delegate and the owner first and
> keeps the closure's own method as the fallback. When neither can take the
> call, it invokes the fallback, discards the result and throws
> {{MissingMethodException}}; invokedynamic catches it and calls the method
> again through {{GroovyObject.invokeMethod}}, so the method runs twice:
> {code:groovy}
> class C { Closure<Integer> withCount() { { -> int n = 0; with { n++ }; n } } }
> Closure<Integer> c = new C().withCount().rehydrate(null, null, null)
> c.resolveStrategy = Closure.OWNER_ONLY
> assert c() == 1 // 2
> {code}
> Called through the meta class directly ({{c.metaClass.invokeMethod(...)}}),
> the call throws {{MissingMethodException}} after running the method. A
> closure without an owner and with {{OWNER_ONLY}}, or with {{DELEGATE_ONLY}}
> and no delegate, reaches the fallback. Expected: the fallback's result is
> returned.
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