Groovy metaprogramming (getProperty) only works when called from outside the class? - groovy

Question

I tried some (runtime) metaprogramming with Groovy. I went ahead and implemented the getProperty method of GroovyInterceptable. But now I found out that this only works when getting a property on the object from the outside. When getting an property from inside a method in that class my getProperty method does not called (see the code example below).
Now, is this expected and has it always been like this? A collegue told me this used to be different in the past (from what he remembers). Is there another way where both property reads from inside and outside would call my getProperty method?
class SomeGroovyClass implements GroovyInterceptable {
def foo
SomeGroovyClass() {
foo = "ctor"
}
def getProperty(String name) {
if (name == "foo") {
return "blub"
} else {
return "foo"
}
}
def test2() {
System.out.println "foo from inside via method call: " + this.foo
}
}
def someGroovyClass = new SomeGroovyClass()
System.out.println "foo from outside: " + someGroovyClass.foo
someGroovyClass.test2()
Output is
foo from outside: blub
foo from inside via method call: ctor

Answer 1

One way to force the use of the getProperty method is to force the type used to access this. Changing your test2 method to:
def test2() {
println "foo from inside via method call: " + ((GroovyInterceptable) this).foo
}
results in:
~> groovy solution.groovy
foo from outside: blub
foo from inside via method call: blub
alternatives to forcing the type:
def test2() {
def me = this as GroovyInterceptable
println "foo from inside via method call: " + me.foo
}
and
def test2() {
GroovyInterceptable me = this
println "foo from inside via method call: " + me.foo
}
I can grok where the groovy compiler is coming from...there really is no way for it to know which handling of the foo property you are looking for unless you are explicit about it.
I believe the main purpose of the getProperty mechanism is to cover access of non-existent properties. This makes defaulting to the existing property when one is available a reasonable choice in my opinion and they still leave the door open as you can always force things using typed access like in the above.