Am 30.07.2013 14:17, schrieb Peter Levart:
[...]
So what would give Groovy or other language runtimes headaches when all
there was was a parameter-less getCallerClass() API? Aren't the
intermediate frames inserted by those runtimes controlled by the
runtimes? Couldn't the "surface" runtime-inserted methods capture the
caller and pass it down? I guess the problem is supporting calling the
caller-sensitive methods like Class.forName(String) and such which don't
have the overloaded variant taking caller Class or ClassLoader as an
argument...
Speaking for Groovy...
those intermediate frames are runtime controlled, yes, but passing down
the caller class is exactly the problem. Imagine I would suggest that
each and every method definition in Java automatically gets an
additional parameter for the caller class, just to have access to it
inside the method. You would not accept that for Java, would you? And so
we cannot accept that for Groovy if we want to keep integration with
Java... and the good integration with Java is one of the key points of
Groovy. Even if we make something like that @CallerSensitive and add the
parameter only in those cases, we break being able to override methods.
Plus, before Groovy3 is not done we have to support several call paths.
And the oldest one, which is still a fallback, does not support
transporting the caller class through the runtime layers at all.
Changing here is a breaking change.
John Rose suggested to "capture" the caller in the "surface" method and
bind it with a MethodHandle and then pass such MH down the runtime API
and finally call that method via MH.
Only that you then need a java7+ only version, plus the already
mentioned problem, that not all of the three general call paths support
that or can be changed in a way to enable that without breaking user code.
bye Jochen
--
Jochen "blackdrag" Theodorou - Groovy Project Tech Lead
blog: http://blackdragsview.blogspot.com/
german groovy discussion newsgroup: de.comp.lang.misc
For Groovy programming sources visit http://groovy-lang.org
