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From Martin Gainty <mgai...@hotmail.com>
Subject RE: Easyant - Plugin conflict management
Date Mon, 26 Aug 2013 22:04:16 GMT
you never looked at plugin-management

understanding what you're criticising before you write a commentary will lend veracity to
your statements


http://maven.apache.org/pom.html#Plugin_Management
Martin Gainty 
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> From: dridi.boukelmoune@zenika.com
> Date: Mon, 26 Aug 2013 20:31:32 +0200
> Subject: Re: Easyant - Plugin conflict management
> To: dev@ant.apache.org
> 
> Hi,
> 
> This is my first post on this mailing list, I used to lurk in the
> previous easant ML and even answer sometimes.
> 
> In this thread I see several points and one of them looks like a
> non-issue to me. Please forgive my heresy when I use maven as an
> example.
> 
> On Tue, Aug 20, 2013 at 6:50 PM, Nicolas Lalevée
> <nicolas.lalevee@hibnet.org> wrote:
> >
> > Le 20 août 2013 à 14:22, Jean-Louis Boudart <jeanlouis.boudart@gmail.com>
a écrit :
> >
> >> I've commited changes on trunk with some unit tests if you want to have a
> >> look.
> >>
> >> Known limitation :
> >> * system plugins doesn't participate *yet* to global plugin resolution
> >> * plugins classpath created dinamically will all contains the whole
> >> resolution graph (not really a problem)
> >>
> >> Point 1 : this can even affect performance. Invoking resolve process one
> >> time seems much more speed that invoking plugins individually.
> >
> > This seems strange to me. Do you have an idea why ?
> 
> I believe he meant this could *improve* performances by sharing a
> single global resolve between all plugins (or something like that).
> 
> >> Point 2 : Even if there is no much activity, i suggest to keep backward
> >> compatibility
> >
> > fine for me.
> 
> Not necessary from my point of view. My only advice is to avoid legacy
> (or technical debt ;) at such early time.
> 
> >> Point 3 : By two steps i meant running a global resolve (for all plugins
> >> and buildtypes including transitive ones). And then have a second class
> >> invoked to perform individual import of ant build file by picking them from
> >> the ResolveReport.
> >
> > ok I see. This make totally sense.
> 
> This is where I'm lost. Actually the whole issue of dependencies
> conflicts between plugins.
> 
> Here is the behavior I think I've observed with Maven:
> - maven resolves project dependencies and does a shitty job at
> conflicts resolution
> - maven resolves plugins dependencies one by one and downloads them lazily
> - each plugin is executed with its own classloader, and doesn't care
> about other plugins dependencies
> - I can get a dozen versions of the infamous[1] plexus-utils in a single build
> 
> My point is, given proper isolation, is it a real issue to have
> different plugins depending on different versions of the same modules
> ?
> 
> At the very least, I like the idea of a single global resolve. Even
> though I understand the benefits of a lazy resolution/download, I
> don't see this as a problem with today's average bandwidth and disk
> space to get every thing needed by a build in a single go. I tend to
> work offline and I hate when I discover in the train that I'm missing
> a dependency :)
> 
> >> You can check ResolvePlugins and ImportDeferred class in trunk if you want
> >> to see concrete stuff.
> >
> > I usually do a very quick review of the code to keep me informed of what is going
on and see if nothing bug me, and as always, it seems great. But I need to get into this more
deeply to see how it really works.
> >
> > Nicolas
> >
> 
> Best Regards,
> Dridi
> 
> [1] it's just that I don't like it :p
> 
> >>
> >>
> >>
> >>
> >> 2013/8/17 Nicolas Lalevée <nicolas.lalevee@hibnet.org>
> >>
> >>> Long overdue response.
> >>>
> >>> Le 3 août 2013 à 13:33, Jean-Louis Boudart <jeanlouis.boudart@gmail.com>
> >>> a écrit :
> >>>
> >>>> Hi there,
> >>>>
> >>>> It becomes necesssary to manage conflicts between plugins.
> >>>> This issues has been raised many time and is referenced on jira[1].
> >>>>
> >>>> Currently easyant offers import task taking some specific attributes
to
> >>>> resolve a plugin (mainly organisation, module name and revision).
> >>>> <ea:import org="mycompany" module="myplugin" revision="x.x"/>
> >>>>
> >>>> This task will :
> >>>> * resolve the given plugin or buildtypr
> >>>> * create a dynamic classpath for this plugin
> >>>> * expose location of others extra files through properties (ex
> >>>> checkstyle.xml containing checkstyle rules, this files is shipped in
the
> >>>> plugin). Thoses properties will then be reused by the plugin itself
> >>>> * import the real ant file (invoke the importTask from ant core under
the
> >>>> hood)
> >>>>
> >>>> This task is currently used :
> >>>> * dynamically by easyant to load system plugins (skeletons for example)
> >>>> * dynamically by easyant when you specify <ea:build> or <ea:plugin>
tags
> >>>> in module.ivy files
> >>>> * invoked in plugin ant file itselfs
> >>>> * invoked in module.ant if users has complex needs
> >>>>
> >>>> Additionnal there is two "alliases" for this task to import plugins
and
> >>>> buildtype.
> >>>> <ea:plugin module="compile-java" revision="0.9"/>
> >>>> <ea:plugin module="build-std-java" revision="0.9"/>
> >>>> If organisation attribute is not specified on aliases default one will
> >>> be
> >>>> used.
> >>>>
> >>>> It does the job but it doesn't handle conflict between plugins.
> >>>>
> >>>> Some plugins relies on abstract ones.
> >>>> Exemple:
> >>>> package-jar depends on abstract-package, abstract-package depends on
> >>>> abstract-compile, but compile-java plugin also depends on
> >>> abstract-compile.
> >>>> Which versi of abstract-compile will be taken in case both plugins load
> >>>> different version ? The answer is the first one !
> >>>> This becomes more problematic on buildtypes, as buildtypes loads a set
of
> >>>> plugins (including themself others abstract-plugins).
> >>>>
> >>>> Ok so now you should have a quick picture of the problem.
> >>>>
> >>>> What could be done ?
> >>>>
> >>>> We can rely on ivy to describe dependency on plugins. But then how could
> >>> we
> >>>> know in which order plugins should be loaded ?
> >>>>
> >>>> I suggest to introduce a deferred import mechanism.
> >>>>
> >>>> We should split responsibility in two distinct steps.
> >>>> 1 - resolve (based on ivy) the whole graph of plugins and store the
> >>> resolve
> >>>> report somewhere as a reusable reference in ant project
> >>>> 2 - invoke a new import task should import already resolved plugins
(the
> >>>> task could rely on the report stored as a reference in ant project)
> >>>>
> >>>> Exemple :
> >>>> compile java will have an ivy dependency on abstract-compile
> >>>> <dependency org="org.apache.easyant.plugins" module="abstract-compile"
> >>>> revision="1.0"/>
> >>>>
> >>>> The compile java ant script will import the resolved plugin
> >>>> <ea:import-deferred org="org.apache.easyant.plugins"
> >>>> module="abstract-compile"/>
> >>>>
> >>>> Note that i'm not fixed yet with the task name. Any suggestion (even
for
> >>>> alliases are welcome).
> >>>>
> >>>> To maintain backward compatibility i'm in favor of creating new aliases
> >>>> "import-plugin" and "import-buildtype" instead of reusing existing ones.
> >>>>
> >>>> People would be able to continue using existing task with known the
> >>>> limitation (no conflict management on plugins).
> >>>> This can help if someone wants to load plugins in module.ant after
> >>> setting
> >>>> a few properties.
> >>>>
> >>>> I also recommend adding a warning on existing task to recommend people
> >>>> using the new import mechanism.
> >>>>
> >>>> What do you think ?
> >>>
> >>> I see 3 points here.
> >>>
> >>> First, managing plugin dependencies: with Ivy, of course, we couldn't
> >>> agree more :)
> >>>
> >>> Then about creating new tasks to keep backward compatibility. I think we
> >>> can break backward compatibility. Easyant is not yet 1.0 and I do not see
> >>> much activity on the user list. I would prefer bugging the current users
> >>> than having an error-prone and deprecated task around.
> >>>
> >>> Third there is the resolve in two steps. I really like the idea. I am not
> >>> sure though if we need this in order to bring conflict management in plugin
> >>> dependencies. And I am not sure how far you are willing to go.
> >>> Actually this is a larger topic which has bugging me recently. The way we
> >>> use the ivy.xml is generally either to tight or insecure. For instance when
> >>> using version ranges in an ivy.xml, since the content of the repository
is
> >>> expected to change over time, then the resolve may change over time since
> >>> new versions might fit the range. Range makes things unreliable over time,
> >>> so often I restrict myself to not use any range. But it's kind of a shame
> >>> to not use ranges in a dependency manager.
> >>> I continued experimenting with the OSGi mapping in Ivy. And the OSGi
> >>> version semantics are very loose. It is because it represents what versions
> >>> of software it is compatible with, not the versions we will be using in
> >>> your specific unit test or application. So relying on OSGi manifest to
> >>> resolve dependencies is not safe at all. That's why I implemented the
> >>> fixdeps [1] task. From a very loose specification of the dependencies, it
> >>> will produce an ivy.xml which is very tight and secure.
> >>> Then, when adding dependencies to a project, we edit the
> >>> ivy-specification.xml and run fixdeps. The build then relies on the
> >>> produced ivy.xml. A nice side effect is that since there is only non
> >>> transitive fixed dependencies to resolve, resolve is fast: either the
> >>> module is here either it's not. And with proper caching, everything works
> >>> with the filesystem.
> >>> But, as wrote above, I'm not sure if that's why you suggested the two
> >>> steps resolve.
> >>>
> >>> Nicolas
> >>>
> >>> [1] http://ant.apache.org/ivy/history/trunk/use/fixdeps.html
> >>>
> >>>
> >>> ---------------------------------------------------------------------
> >>> To unsubscribe, e-mail: dev-unsubscribe@ant.apache.org
> >>> For additional commands, e-mail: dev-help@ant.apache.org
> >>>
> >>>
> >>
> >>
> >> --
> >> Jean Louis Boudart
> >> Independent consultant
> >> Apache EasyAnt commiter http://ant.apache.org/easyant/
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: dev-unsubscribe@ant.apache.org
> > For additional commands, e-mail: dev-help@ant.apache.org
> >
> 
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