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.
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