Re: [xwiki-devs] [Proposal] Change our Script API best practice regarding exception handling (Take 2)

On 03 Apr 2016, at 10:49, Thomas Mortagne <thomas.mortagne(a)xwiki.com> wrote: You will start catching when you want to deal with errors (before that the Velocity macro will deal with it for you automatically) and it does not really cost much more lines to deal with errors that way than using checking for null return (for method that actually return something that could be null to indicate errors) and getLastError() concept like we do now.

On Sun, Apr 3, 2016 at 12:19 AM, Eduard Moraru <enygma2002(a)gmail.com> wrote: > +0 > > I can`t help but feel we are stretching Velocity more than what it was > built for and we might end up with a more verbose and spaghetti code than > what we would have liked (and than we currently have). > > As long as we try not to abuse it, I guess we can see how it goes. > > Thanks, > Eduard > > On Sat, Apr 2, 2016 at 11:59 AM, Vincent Massol <vincent(a)massol.net> wrote: > >> >>> On 01 Apr 2016, at 23:04, Sergiu Dumitriu <sergiu(a)xwiki.org> wrote: >>> >>> I think that it's a good idea for script services to throw somewhat >>> expected exceptions, signalling invalid usage attempts (user not >>> authorized, wrong arguments...) that would then be caught in Velocity. >>> But deeper platform issues (DB errors, unexpected NPE, OOM...) should be >>> handled outside the user's code itself, at the skin level (view.vm). >> >> Sure, that’s the point. The scripts can decide to catch or not (ie. to >> handle or not). If not then it’s caught anyway at the level of >> MacroTransformation (for macros) or at the level of contentview.vm. In the >> majority of cases there isn’t much that the script can do and it shouldn’t >> catch anything (it should catch only if it can handle it, i.e. do something >> with the exception). >> >> Thanks >> -Vincent >> >>> >>> On 04/01/2016 05:45 AM, Vincent Massol wrote: >>>> So far we have the following devs who agree: >>>> - thomas >>>> - marius >>>> - vincent >>>> >>>> What about Edy, Sergiu and the others? >>>> >>>> Thanks >>>> -Vincent >>>> >>>>> On 31 Mar 2016, at 14:17, Vincent Massol <vincent(a)massol.net> wrote: >>>>> >>>>> Guys, I’d like that we progress on this. >>>>> >>>>> I didn’t get any agreement or disagreement to this proposal. >>>>> >>>>> Any take? >>>>> >>>>> Thanks >>>>> -Vincent >>>>> >>>>> >>>>>> On 18 Jan 2016, at 11:03, vincent(a)massol.net wrote: >>>>>> >>>>>> Hi devs, >>>>>> >>>>>> After a lot of thinking and experimentation (see the thread’s >> details), I have found that this first proposal is not a good idea. I’m >> thus proposing to replace it with the following best practice: >>>>>> >>>>>> * Let our script services generate exceptions >>>>>> * If the velocity scripts with to handle the exceptions, then they >> should use the #try() directive. If they don’t want to, they don’t have to >> do anything since the MacroTransformation or the template (contentvars.vm >> for example) will catch it and display it to the user. >>>>>> >>>>>> More precisely I’m proposing that: >>>>>> >>>>>> * Existing Script APIs in Java should not be modified as that would >> break backward compatibility. New signatures can be added and old one >> deprecated and moved to the legacy modules. After new signatures have been >> introduced, existing velocity scripts can be updated to use the new >> signatures and to use the #try directive if needed. >>>>>> * New Script APIs must use the new best practices (if agreed :)), >> i.e. throw Exceptions, and new velocity scripts must use the #try() >> directive if they need to handle exceptions. >>>>>> >>>>>> WDYT? >>>>>> >>>>>> Thanks >>>>>> -Vincent >>>>>> >>>>>> >>>>>> On 14 Jan 2016 at 17:51:04, vincent(a)massol.net (vincent(a)massol.net >> (mailto:vincent@massol.net)) wrote: >>>>>> >>>>>>> Hi devs, >>>>>>> >>>>>>> Right now our strategy is for script services and script APIs in >> general to catch exceptions, store them and offer a getLastError() method >> to get them (see >> http://extensions.xwiki.org/xwiki/bin/view/Extension/Script+Module#HBestPra… >> ) >>>>>>> >>>>>>> However it would be much nicer to: >>>>>>> * Let our script services generate exceptions >>>>>>> * Offer a velocity script service to get the last exception raised >> by a java call from velocity >>>>>>> * Implement this uberspector to catch the exceptions and to set them >> in the execution context >>>>>>> >>>>>>> That should be quite easy to implement IMO. >>>>>>> >>>>>>> WDYT? >>>>>>> >>>>>>> Thanks >>>>>>> -Vincent >>>>>>> >>>>>>> PS: This is http://jira.xwiki.org/browse/XWIKI-2374