[Yanel-dev] exception handling in Ant tasks

[Guillaume Déflache]

Michael Wechner schrieb:
> Guillaume Déflache wrote:
>> Michael Wechner schrieb:
>>> Guillaume Déflache wrote:
>>>> Could we stop logging exceptions in Ant tasks and simply rethrow 
>>>> them as build exceptions (org.apache.tools.ant.BuildException).
>>>> The Ant tasks's "execute" entry-point method that every task shall 
>>>> implement already throws this type of exception so by only 
>>>> (re)throwing it here and in other methods:
>>>> - the stacktraces are simpler because they don't get displayed 
>>>> and/or wrapped many times
>>>> - one does not litter one's code with a lot of exception handling, 
>>>> the only needed code is "throws BuildException" appended on all 
>>>> methods signatures, or even "throws Exception" with only a exception 
>>>> wrapper from Exception to BuildException on the "execute" method
>>>> - errors ultimately get catched by Ant anyway, which already does a 
>>>> great job at showing full stacktraces, *and failing the whole build*
>>>>
>>>>
>>>> I am asking because I spent quite some time wondering why my 
>>>> resource-type was not found, it was only because my project's 
>>>> resource-types.xml was not well-formed and it just got ignored 
>>>> because of these issues (culprit here being Yanel's 
>>>> src/build/java/org/wyona/yanel/ant/MergeResourceTypesConfigsTask.java)... 
>>>>
>>>>
>>>> Better fail fast than silently!!!
>>>
>>> I understand your frustration, but you need to be more specific by 
>>> providing a patch of the MergeResourceTypesConfigsTask class
>>
>> Shall I do that now?
>> The modification is pretty systematic as I tried to explain: remove 
>> all "try { ...} catch" constructs and make all methods throws 
>> Exception. Only the 'execute' method's contract will only allow 
>> BuildException to be thrown so wrap Exception to BuildException there.
> 
> rather not, because I do not think we should "replace" *all* try/catch  
> statements, but we really need to spend time on each case.
> 
> I will now implement the case of not well-formed resource-types.xml

OK.


>>> re which errors you want to throw and give specific examples when 
>>> these errors are thrown, e.g. resource-types.xml is not well-formed.
>>
>> I already gave an example:
>> make your realm's resource-types.xml not well-formed => the build will 
>> not break
> 
> it didn't sound like this was the only case/example

Really it was sound-distortion by frustration! ;)
I had other problems because I thought the resource-types.xml has to be 
placed directly under the realm directory (where build.xml is located) 
whereas it has to be in the same directory as the realm configuration 
file (e.g. realm.xml).


>> Sadly you cannot provide an example log since AFAICS the errors do not 
>> show up on the console, at least not at the log level I usually run 
>> Ant (with ANT_ARGS=-q).
> 
> maybe you should consider running without -q
> 
>> Where are the log4j logs supposed to be written to in this case?
> 
> I think it's standard output/command line

Indeed, maybe not using -q would have revealed this.


>> I am not sure which log4j properties file gets read here.
> 
> I am not sure either and would have to check
> 
> 
>>
>>> The case that your resource-types.xml is not found is NOT a build 
>>> error, because a realm does not have to have such a file.
>>
>> It was a misformulation from my side, I should have written
>> "spent quite some time wondering why my resource-type was not taken 
>> into account" instead of "spent quite some time wondering why my 
>> resource-type was not found".
>> I am aware this file is not mandatory.
> 
> ok, maybe you want to add this to the documentation

I will.


>>> That's rather a matter of documentation. Also you could enhance this 
>>> documentation, e.g.
>>>
>>> http://www.yanel.org/en/documentation/configuration/resource-types_xml.html 
>>>
>>> http://www.yanel.org/en/documentation/create-new-resource.html
>>
>> We certainly could expand 
>> http://www.yanel.org/en/documentation/configuration/resource-types_xml.html 
>> with a rationale for the example and at 
>> $YANELHOME/conf/local/local.resource-type.xml in the "Register New 
>> Resource" section suggest to use $REALM_DIR/resource-types.xml instead 
>> of $YANEL_HOME/conf/local/local.resource-types.xml
>>
>> Should I do that now?
> 
> yes, that would be great

OK, doing that now.

I'll add another simpler example for project-specific resource-types.xml 
files (taken from the from-scratch realm) as the existing one is rather 
lengthy.

BTW I noticed that for project-specific resource-types.xml files on 
'resource-type' elements:
- AFAICS the 'src' attributes do not have to end with "/" to work
- the paths for these attributes are also really relative to the 
directory where the realm configuration file (e.g. realm.xml) is, not to 
the realm directory (where build.xml is)
I will document the second point, but I won't document the first as I am 
not so sure it works in all cases (with 'copy-dir-name' attribute for 
example) so I will only experiment that on my current project and see if 
it goes well.