Hi everyone,
I wanted to start another discussion having to do with POM interpolation
in the upcoming Maven 2.0.10 release. If you recall, I previously sent
out a proposal for retaining dynamic expressions in the build section of
the POM, to allow updates to that section that take place via plugin
execution to be reflected in subsequent executions.
This proposal is somewhat different, and is mostly orthogonal to that
previous discussion. This proposal is less about _when_ we interpolate
different parts of the POM, and more about _how_ we do it. Since before
its original release, Maven has used a single-class implementation of
the ModelInterpolator used to resolve expressions in the POM. As we
learned more about what we needed to support in POM expressions - and,
what the order of operations was for interpolating - this single class
quickly grew into quite a beast of tangled conditional logic and loops.
Even the interface and the code surrounding the call to that interface
were abused more than a little, as we tried to trick the interpolator
into making exceptions of certain parts of the POM, and prioritizing
certain sources of expression values over others.
The full proposal is here:
http://docs.codehaus.org/display/MAVEN/POM+Interpolation+Refactor
As a brief synopsis:
For anyone who has tried to improve the interpolator ahead of a 2.0.x
release, you already know what I'm talking about; the interpolator has
been limping along for some time now. For anyone who hasn't spent much
time on this functionality, a quick scan of JIRA for any given release
will show you how persistent and varied the interpolation problems have
been. It has reached the point where solving these problems within the
current implementation often requires threading your way through rules
that seem diametrically opposed to one another.
At the same time, I've been working on the interpolation code in
plexus-utils for use in the Assembly plugin (and though I'm not sure who
you are, I know others are using plexus-utils for interpolation as
well). I believe this code has reached a level of maturity and
sophistication that will allow us to replace the original interpolator
in maven-project with a less-complex solution implemented around this
plexus-utils code. However, because of the historic problems with
plexus-utils in Maven, and because plexus-utils contains several other
hotspots of variability like the CLI code used to fork child processes,
I split this interpolation code out into a new library called
plexus-interpolation. The old plexus-utils classes now depend on
plexus-interpolation, which is shaded into plexus-utils until those
deprecated classes can be removed.
Additionally, I've implemented this refactor on a feature branch, so you
can take a look at:
https://svn.apache.org/repos/asf/maven/components/branches/john-2.0.x-plxInterpolation
to see the actual implementation.
Please take a look and tell me what you think.
Thanks,
-john
--
John Casey
Developer, PMC Member - Apache Maven (http://maven.apache.org)
Blog: http://www.ejlife.net/blogs/buildchimp/
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
