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https://issues.apache.org/jira/browse/GROOVY-12667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18137432#comment-18137432
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ASF GitHub Bot commented on GROOVY-12667:
-----------------------------------------
codeconsole opened a new pull request, #3188:
URL: https://github.com/apache/groovy/pull/3188
An implicit-this method call from a closure whose resolve strategy is
`DELEGATE_FIRST` and whose delegate is null is sent to `NullObject`. Instead of
reaching the owner, it throws `NullPointerException: Cannot invoke method foo()
on null object`:
```groovy
class Owner {
def foo() { 'owner' }
def test() {
def c = { -> foo() }
c.resolveStrategy = Closure.DELEGATE_FIRST
c.delegate = null
c()
}
}
assert new Owner().test() == 'owner' // NPE since 4.0.0
```
`OWNER_FIRST` with a null owner (the delegate is never tried) and a
dehydrated closure behave the same way. A method neither candidate has throws
the NPE instead of `MissingMethodException`. Since GROOVY-11858, `toString()`
and `is(x)` in such a closure run against `NullObject`. Groovy 3 skipped a null
delegate or owner, and `Closure.getProperty` still does. Seen in 4.0.33, 5.0.8
and 6.0.0.
GROOVY-7232 dropped the `instanceof GroovyObject` check from the
`DELEGATE_FIRST` and `OWNER_FIRST` branches of `ClosureMetaClass.invokeMethod`
so that non-Groovy delegates work, and that also let null through. Those
branches now require a non-null delegate or owner before trying it. The
`*_ONLY` branches already exclude null.
This and #3185 (GROOVY-12664) change different lines of
`ClosureMetaClass.invokeMethod`; both append tests to `ClosureDelegationTest`.
## Tests
`ClosureDelegationTest` gains `testDelegateFirstWithNullDelegate` (owner
method, `toString()` and `is`),
`testDelegateFirstWithNullDelegateStaticContext`,
`testDelegateFirstWithNullDelegateTypeChecked`, `testOwnerFirstWithNullOwner`,
`testMissingMethodWithNullDelegate` and `testDehydratedClosureMissingMethod`.
All six fail without the change. `groovy.lang.*Closure*`, `groovy.*Closure*`,
`gls.invocation.*`, `org.codehaus.groovy.runtime.*`, `groovy.transform.stc.*`,
`org.codehaus.groovy.classgen.asm.sc.*` and `groovy.ThisAndSuperTest` pass. The
Checkstyle and CodeNarc gates pass.
> Implicit-this call in a DELEGATE_FIRST closure with a null delegate throws
> NullPointerException instead of calling the owner
> ----------------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12667
> URL: https://issues.apache.org/jira/browse/GROOVY-12667
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.0.8, 7.0.0-alpha-1, 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> class Owner {
> def foo() { 'owner' }
> def test() {
> def c = { -> foo() }
> c.resolveStrategy = Closure.DELEGATE_FIRST
> c.delegate = null
> c()
> }
> }
> assert new Owner().test() == 'owner'
> {code}
> *Actual:* {{java.lang.NullPointerException: Cannot invoke method foo() on
> null object}}. The same happens for OWNER_FIRST with a null owner (the
> delegate is never tried), for a dehydrated closure, and for a method that
> neither candidate has (NPE instead of MissingMethodException). Since
> GROOVY-11858, {{toString()}} in such a closure returns "null" and
> {{is(null)}} returns true, because they run against NullObject.
> *Expected:* a null delegate (or owner) is skipped and the other candidate
> answers, as in Groovy 3 and as property access ({{Closure.getProperty}})
> still does. When neither answers, a MissingMethodException is thrown.
> Cause: GROOVY-7232 removed the {{instanceof GroovyObject}} check from the
> DELEGATE_FIRST and OWNER_FIRST branches of {{ClosureMetaClass.invokeMethod}},
> which also let a null delegate or owner through to
> {{InvokerHelper.invokeMethod(null, ...)}}.
> Verified: 4.0.33, 5.0.8, 6.0.0 and master affected; 3.0.25 and 2.4.15 not
> affected.
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