RFR: 8220715 JEP Draft: Add detailed message to NullPointerException describing what is null

[Lindenmaier, Goetz]

Hi,

This JEP proposes to enhance the messages of NullPointerExceptions
that are thrown if execution of a bytecode fails due to a null reference.
https://bugs.openjdk.java.net/browse/JDK-8220715
A corresponding prototype exists and is submitted to the sandbox 
repo and is available as change 8218628.

I already got valuable input on this topic by Mandy:
http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-March/033115.html

Is anyone else interested in commenting on this?
Would someone sponsor this JEP?

Best regards,
  Goetz.



> -----Original Message-----
> From: Lindenmaier, Goetz
> Sent: Freitag, 15. März 2019 11:55
> To: 'mark.reinhold at oracle.com' <mark.reinhold at oracle.com>;
> maurizio.cimadamore at oracle.com
> Cc: mandy.chung at oracle.com; roger.riggs at oracle.com; core-libs-
> dev at openjdk.java.net; hotspot-runtime-dev at openjdk.java.net
> Subject: RE: RFR(L): 8218628: Add detailed message to NullPointerException
> describing what is null.
> 
> Hi everybody, Mark,
> 
> I followed your advice and created a JEP:
> https://bugs.openjdk.java.net/browse/JDK-8220715
> 
> Please point me to things I need to improve formally, this is my first
> JEP. Also feel free to fix the administrative information in the
> Jira issue if it is wrong.
> 
> And, naturally, you're welcome to discuss the topic!
> 
> Best regards,
>   Goetz.
> 
> > -----Original Message-----
> > From: mark.reinhold at oracle.com <mark.reinhold at oracle.com>
> > Sent: Donnerstag, 14. März 2019 22:38
> > To: maurizio.cimadamore at oracle.com; Lindenmaier, Goetz
> > <goetz.lindenmaier at sap.com>
> > Cc: mandy.chung at oracle.com; roger.riggs at oracle.com; core-libs-
> > dev at openjdk.java.net; hotspot-runtime-dev at openjdk.java.net
> > Subject: Re: RFR(L): 8218628: Add detailed message to NullPointerException
> > describing what is null.
> >
> > 2019/3/14 8:00:20 -0700, maurizio.cimadamore at oracle.com:
> > > I second what Mandy says.
> > >
> > > First let me start by saying that this enhancement will be a great
> > > addition to our platform; back in the days when I was teaching some Java
> > > classes at the university, I was very aware of how hard it is to
> > > diagnose a NPE for someone novel to Java programming.
> >
> > Agreed!
> >
> > > ...
> > >
> > > I also think that the design space for such an enhancement is non
> > > trivial, and would best be explored (and captured!) in a medium that is
> > > something other than a patch. ...
> >
> > Agreed, also.
> >
> > Goetz -- if, per Mandy’s suggestion, you’re going to write something
> > up using the JEP template, might I suggest that you then submit it as
> > an actual JEP?  Giving visibility to, and recording, such design-space
> > explorations is one of the primary goals of the JEP process.
> >
> > - Mark