Strange question but maybe it will inspire someone else. Why does the POM the
user uses to control the build the exact same format as the POMs created to
express the results of the build? Is that necessary? It seems to me the
discussion is about the drawbacks of that approach. Perhaps its needed for
reproducible builds or something but it seems to me those two use cases are
different and the difficulty comes from trying to make one stable format serve
both use cases.
Hunter
On Sunday, June 11, 2023 at 02:12:49 PM PDT, Romain Manni-Bucau
<rmannibu...@gmail.com> wrote:
Le dim. 11 juin 2023 à 22:28, Guillaume Nodet <gno...@apache.org> a écrit :
> Those are actually two different questions, but I'd like to raise those
> together, since they do affect the same feature.
>
> 1/ We currently don't have an XML schema for the build POM. One
> possibility would be to relax a bit the constraints on the main POM schema
> (
> http://maven.apache.org/xsd/maven-4.0.0.xsd) so that some elements are not
> mandatory in the xml. By not modifying the validation rules, those
> elements will have to be present in the object model, so that should be
> safe. Another option would be to have a separate schema, but given the
> small set of changes on the build pom on the current constraints, i
> think the first solution would be better. As a reminder, the build pom
> supports: inferring version for artifacts that are part of the reactor
> (that's usually done using managedVersion), inferring the relativePath
> element, ci friendly interpolation for the version.
>
+1 to relax
>
> 2/ the consumer POM could be streamlined much more using the same
> techniques than used in the flatten-maven-plugin. Currently, we're only
> removing the <modules> element, but we could remove the full build section,
> flatten dependencies, etc... Packaged artifacts (i.e. with a non pom
> packaging), can only be used as dependencies, so I think the whole
> flattening process could make sense. Is there any drawback in doing so ?
> Any particular reason the consumer POM support is limited to removing
> modules and does not go further ? I can see some discussion in
> https://cwiki.apache.org/confluence/display/MAVEN/Build+vs+Consumer+POM
> but
> those do not seem to be settled.
>
Doesnt flattening break transitive dep resolution since depth changes?
Also drops some build meta which cant be resoled anymore portably like
compiler setup, which graalvm version was used and lastly would need to
drop or not props not used elsewhere.
Think staying as close as possible of the source is overall good to consume
as intended (build control) until the transformer is fully configurable
(never hopefully since it sounds overcomplicated).
> Le ven. 9 juin 2023 à 11:22, Guillaume Nodet <gno...@apache.org> a écrit :
>
> >
> >
> > Le ven. 9 juin 2023 à 08:59, Hervé Boutemy <herve.bout...@free.fr> a
> > écrit :
> >
> >> adding a new POM element in build POM was supposed to be something for
> >> Maven 5
> >> and to trigger a POM 5 version, to make clear that we are leaving the
> >> Maven 3
> >> space (that uses POM version 4, hence the need for version clarification
> >> between Maven and it POM model version)
> >>
> >> if we enter that space before having released Maven 4, we're adding more
> >> complexity: do you really want to work on Maven 5 now?
> >>
> >>
> >> another aspect:
> >> do we want to have this new improvement only for Maven 4/5 or also have
> >> it for
> >> Maven 3.9?
> >> in Maven 3.9, such little enhancement were implemented as XML attributes
> >>
> >
> > Fwiw, if I reduce the diff between the XSD generated with 3.0 and with
> > 3.9.x, I end up with the following diff
> > https://gist.github.com/gnodet/f8dfd3206ebf55d6e4610a25e683120b
> > So, you're right, no new elements have been introduced. A few attributes
> > added, one element removed.
> >
> > However I really don't understand how adding an attribute vs an element
> > makes the POM more compatible. Our own generated parser will reject any
> > unknown new attribute the same way as an unknown element (that's for any
> > maven 3.x version). Here's what happen if I use a maven 3.2.5 to read a
> POM
> > with an element that has been introduced later:
> > https://gist.github.com/gnodet/35a3ad4d449e586dc282c08eacc82ed0
> > So I'm not really buying the argument about attribute / element at this
> > point. If that could be clarified, it would be nice !
> >
> > So I think the question comes down to: do we prefer modifying/overwriting
> > the schema as we did in the past or do we prefer cleanly versioning it.
> In
> > both cases, I think we need to keep it compatible, i.e. only add
> > elements/attributes. The first option is much easier to implement: just
> do
> > nothing as we did in the past, but this has the drawback of not giving
> > people/tools much warning or information about possible changes. We
> simply
> > overwrite the schema from the web site with the latest one at each
> release,
> > hoping that tools will not see the change and that they don't really
> cache
> > the schema (in case you really need the latest). The other option is to
> > more properly version the schema. This would need additional code if we
> > want to correctly detect which version is the lower version needed to
> > correctly write a given POM. But even for doc changes, I think it may be
> > preferable to micro version the schemas.
> >
> > The scm.child.xxx attributes that were added are not meaningful for the
> > consumer afaik: they are used for build time and for doc, when you use an
> > artifact as a dependency (i.e. on the consumer side), those attributes
> > won't be used. So from a consumer POV, they don't carry any semantics
> and
> > can safely be silently discarded. This is also the case for this new
> > priority attribute, as it only affects the current project or child
> > projects. In that sense this new feature could just be silently added to
> > the schema as previous things, so I'm fine with not versioning the schema
> > now if that's the consensus.
> >
> > The problem (and that's really something we need to fix), is that we
> don't
> > any real difference between the build POM and the consumer POM schemas.
> We
> > also don't make a real difference between consuming as a bom /
> dependency /
> > plugin, and consuming as a parent. Both cases are really different, as
> the
> > first one could strip out most of the <build> section. One possibility
> > would be to more formerly identify those 3 use cases (build on file
> system,
> > consuming as a dependency and consuming as a child). Note that we're
> > currently lacking a build schema, so that when using the build/consumer
> > POM, your build schema cannot be validated, as it's missing some
> elements.
> > One possibility would be to simply make some elements non mandatory in
> the
> > schema. The model validation would check those anyway. For the consumer
> > POM for non "pom" packaging, would it make sense to streamline the
> uploaded
> > POM even more: i.e. remove all build stuff from it (pluginRepositories,
> > pluginManagent, plugins, reporting, etc...) or is there any use case for
> > keeping those ? We could attach the build pom (i.e. we're currently
> > switching the POM when installing/deploying it, but it's attached with a
> > "consumer" classifier during the build).
> >
> > Guillaume
> >
> >
> >>
> >> and of course, independently from this XML mapping and version details,
> >> there
> >> is the question to be seriously discussed about the feature itself: is
> >> this
> >> opportunity of introducing the "priority" field something we want (that
> >> reuses
> >> an implementation that is de-facto already existing internally for a
> long
> >> time, it just exposes it)
> >>
> >> Regards,
> >>
> >> Hervé
> >>
> >>
> >> Le jeudi 8 juin 2023, 22:56:27 CEST Guillaume Nodet a écrit :
> >> > While working on an issue [1], I've raised a PR [2] which is adding an
> >> xml
> >> > element to the POM. So I raised the model version to 4.2.0. My
> >> > understanding is that the build/consumer POM feature [3] was created
> so
> >> > that we could keep compatibility. This is clearly indicated in the
> wiki
> >> > page: "Maven is stuck on POM v4 for a long time now, because changing
> >> the
> >> > POM version and publishing artifacts on Maven Central with this new
> >> model
> >> > would break consumers using either older Maven versions or other build
> >> > tools (that use POM v4 as a compatibility format)."
> >> >
> >> > However, I think this axiom is false. What happens, is that all maven
> >> > versions are perfectly capable of consuming any model when used as a
> >> BOM /
> >> > dependency / plugin, as the parser simply ignores any unknown
> attribute
> >> or
> >> > element. I can install a jar with the 4.2.0 model and consume it with
> >> any
> >> > 3.x version without any problem. The only issue is when using that
> >> project
> >> > as a parent, in which case, the validation is strict and fails with
> the
> >> > 4.2.0 model.
> >> >
> >> > So, saying that "new model would break consumers using [...] older
> Maven
> >> > versions" is just wrong, as they work perfectly when consuming the POM
> >> as
> >> > dependencies. I can create a small git repo if you want to
> experiment,
> >> but
> >> > that has been first checked by @cstamas, then double checked by
> myself.
> >> >
> >> > Now, the discussion is whether we want to allow modifications to the
> POM
> >> > model and support new versions of it. I think this would be quite
> safe,
> >> > provided that there's no incompatible changes, i.e. it's only adding
> new
> >> > elements/attributes.
> >> > I don't think this goes against the build/consumer feature, as I think
> >> the
> >> > main benefit of this feature is to allow default values using sane
> >> > conventions (mainly the project layout on the file system, which is
> not
> >> > available anymore in the remote repository, so this data has to be
> >> present
> >> > for consumers).
> >> >
> >> > So, the question: should we go ahead and allow introducing newer POM
> >> models
> >> > to bring in a few features that have been delayed for a long time
> >> because
> >> > the assumption was that the model could never change ? One
> possibility
> >> to
> >> > minimize the disruption would be to have a smart POM writer : i.e. it
> >> could
> >> > transform the POM to a 4.0.0 model if no new features are actually
> >> used, so
> >> > that only projects actually using the newly introduced features would
> >> > actually use the 4.x pom version.
> >> >
> >> > Guillaume
> >> >
> >> > [1] https://issues.apache.org/jira/browse/MNG-7804
> >> > [2] https://github.com/apache/maven/pull/1147
> >> > [3]
> >> https://cwiki.apache.org/confluence/display/MAVEN/Build+vs+Consumer+POM
> >>
> >>
> >>
> >>
> >>
> >> ---------------------------------------------------------------------
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> >>
> >>
> >
> > --
> > ------------------------
> > Guillaume Nodet
> >
> >
>
> --
> ------------------------
> Guillaume Nodet
>
