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From Nicolas Lalevée <nicolas.lale...@hibnet.org>
Subject Re: Dependency management of the easyant plugins
Date Tue, 03 May 2011 15:11:07 GMT
Just a little mail to say that I didn't forgot this thread, I just don't have much free time
nowadays, I'm about to switch jobs.

see you
Nicolas

Le 24 avr. 2011 à 01:21, Jean-Louis Boudart a écrit :

> Le 22 avril 2011 13:43, Nicolas Lalevée <nicolas.lalevee@hibnet.org> a écrit
> :
> 
>> I would like to discuss the way the plugins are declaring the dependencies
>> with each other.
>> 
>> In easyant 0.8, there was some easyant include. Since it is an include and
>> not an import, each plugin is somehow embedding its dependencies at runtime
>> without directly exposing them to the plugins which are dependencies of it.
>> So if two plugins wants to share some targets, they shouldn't declare these
>> dependencies, it would be the responsibility to the one which includes them
>> both to also include the plugin in common.
>> 
>> In the refactoring of EASYANT-27 [1], I changed the includes with imports
>> so there is no transitive issue about using extension point. Using extension
>> point is kind of different of phases since the dependencies between targets
>> are now explicit. Phases were the workflow every plugins was relying on. Now
>> each plugin expose its points of extension, so each plugins is actually
>> relying on each other. So include was not possible.
>> I hope this is OK for everyone ?
>> 
> Change on import vs include looks good for me even if we loose the ability
> to "alias" a module.
> Prefixing all targets of a plugins by hand will be error prone but maybe we
> can find a workaround for this.
> 
> If i understand correctly, buildtype are supposed to load a set of plugins
> and plug them through their extensionPoint, am i wrong ?
> At first glance it seems to offer much more flexibility than what we had
> before.
> 
> Let's now discuss about "build lifecycle".
> In easyant early stages we used a set of phases defining dependency between
> each others.
> Some plugins was "plugged by default" to standard phases. And buildtypes
> were loading standard phases and sets of plugins.
> There is at least two drawback of this solution :
> 
>   - As a enduser it was a bit confusing as you seen  all "PHASES" even if
>   they don't contains any target. I guess enduser will all the time call the
>   same phases (compile, test, package, verify, release) but will probably
>   never call most of existing phases like process-sources etc...
> 
> 
>   - Another drawback of this model was the coupling between plugins and
>   phases. How someone can use it's own "lifecycle" ? Should he rebind all
>   targets to his own phases ?
> 
> 
> First can be addressed by exposing "high level target" for end users such as
> compile, test, package, verify, etc.. (i'm not sure we need more). To limit
> "copy/paste" between all our buildtype we should put thoses "high level
> target" in a common plugin.
> 
> Second point is defacto addressed by your refactoring.
> 
> My last comment on the refactoring would be about relations between plugins.
> I don't think we need to link plugins except if we had a good reason for it.
> And if we need to link two plugins it would probably better to link on an
> extensionPoint provided by an abstract module. In other cases linking
> plugins should be done by buildtypes or by the enduser itself.
> 
> For example compile-java <import> ivy-provisioning. This sounds like a bad
> choice for me as provisioning (filling a classpath for compilation) can be
> done by others plugins such as "deps-lib".
> In opposite i really like how cobertura / emma plugins interacts with tests
> plugins.
> Both cobertura and emma plugins relies on test extension points defined in
> an abtract-test plugin.
> 
> 
> 
> 
>> 
>> Then I would like to go further. Because each plugin manage its own
>> dependency, each import is an Ivy resolve behind the hood, there is not much
>> dependency management of the plugins. Ivy is here barely used more than just
>> downloading build files. There is no transitive dependency or conflict
>> management.
>> For instance:
>> * build-std-java imports compile-java and ivy-provisioning
>> * compile-java imports ivy-provisioning
>> In this example, ivy-provisioning is resolved two times, and it is possible
>> that the two resolved versions are not the same.
>> 
>> I then suggest to move to a real dependency management of the plugins, by
>> really using Ivy. Each plugin rather than importing himself its
>> dependencies, it would just declares them. As a proof of concept, I
>> implemented an Ant task that just does that. See the "experiment" folder I
>> have just committed to test it.
>> To run the sample, put the jars of both easyant and ivy into
>> sample/ea-jars.
>> Two special ant properties controls the task behaviour:
>> * easyant.refresh : set it to true to force a resolve. Otherwise the last
>> resolve report will be used
>> * easyant.localrepo.basedir : set folder in which the scripts are
>> retrieved, useful for embedding the build. If not set, the scripts are
>> imported directly from the cache.
>> 
>> As you could see the plugin dependencies are nicely resolved. So nicely
>> that a script can have dependencies reusable in the script itself. See the
>> script of org.apache.easyant#groovyfrontend. The classpath to find the
>> project helper is computed by Ivy from the ivy.xml of the plugin.
>> 
>> WDYT of the idea ?
>> 
> 
> BIG +1 :)
> 
> -- 
> Jean Louis Boudart
> Independent consultant
> Project Lead http://www.easyant.org


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