Re: [m2e-users] Using M2E metadata in Joda-Beans maven plugin

[Igor Fedorenko <igor@xxxxxxxxxxxxxx>]

Double error markers is a known limitation of the legacy "plexus"
BuildContext API that you use. I was about to suggest takari
incrementalbuild library [1] as the solution, but it does not support
in-place changes to the build input files, so won't work for Joda-Beans.

As for java recompilation, I am not sure. It does sound like a JDT
problem, so unless you want to learn how to debug Eclipse JavaBuilder,
I'd just keep the hack.

If you decide to dig deeper into this, I am happy to give some pointers,
but please use m2e-dev mailing list for further questions.

[1] http://takari.io/2014/03/25/incremental-build.html

--
Regards,
Igor

On 2014-12-31 6:24, Stephen Colebourne wrote:
> Hi all,
> I've recently added M2E metadata to the Joda-Beans maven plugin to
> better support Eclipse:
> https://github.com/JodaOrg/joda-beans-maven-plugin/commit/1fbd8eadc42c1bec70f2f5079e027289851a51ca
>
> Joda-Beans is a source code generator that takes a developer edited
> .java source file and adds autogenerated code (to the same source
> file). For example:
> https://github.com/JodaOrg/joda-beans/blob/v1.4/src/test/java/org/joda/beans/gen/UserAccount.java#L34
> I believe that Joda-Beans editing the original .java file (rather than
> creating a new .java file) is unusual in the realm of maven-plugins
> and m2e.
>
> The first change to include the m2e metadata xml file in
> joda-beans-maven-plugin (rather than each end-user pom.xml) worked
> well - good job!
>
> The second change was to use the execute/runOnIncremental=true mode to
> get Eclipse to dynamically regenerate the code when the file is
> edited. Adding basic use of BuildContext (refresh and addMessage)
> worked OK, but things got more complicated and my final solution feels
> hacky.
>
> One minor problem was that I end up with two errors in Eclipse when
> there is a problem. One error marker appears in the pom.xml file from
> the thrown MojoFailureException and one error marker appears in the
> source file from buildContext.addMessage() (as expected/desired). Is
> there any way to avoid the MojoFailureException adding an error
> marker?
> https://github.com/JodaOrg/joda-beans-maven-plugin/commit/1fbd8eadc42c1bec70f2f5079e027289851a51ca#diff-7b40ac75b969c88992c998201847ce0aR371
>
> The main problem was that calling buildContext.refresh() on the
> updated .java source file was insufficient to properly refresh the
> file. Calling buildContext.refresh() on the updated .java file caused
> Eclipse to reload the .java source file and correctly update some
> internal state. However, it did not trigger a full recompilation of
> that source file, which resulted in error markers (I think the source
> file was in some way partially recompiled). Those error markers could
> be solved by forcing a rebuild of the source file (such as adding and
> deleting a space in the .java source file, or using the Project/Clean
> menu in Eclipse).
>
> To solve this, I found a hacky solution. As well as calling
> buildContext.refresh() on the updated .java source file, I also delete
> the matching compiled .class file from target/classes. This results in
> what appears to be a "double refresh" in Eclipse - first the
> previously observed buildContext.refresh() error markers appear, and
> then Eclipse recompiles the file (because the .class file is missing)
> and the error markers disappear. Note that I tried calling
> buildContext.refresh() on the .class file but that had no effect.
> https://github.com/JodaOrg/joda-beans-maven-plugin/commit/1fbd8eadc42c1bec70f2f5079e027289851a51ca#diff-7b40ac75b969c88992c998201847ce0aR219
>
> While hacky, the plugin does now work well. Eclipse can now be setup
> such that any edit to a Joda-Bean .java source file causes the file to
> be regenerated and recompiled, without needing to learn how to write
> an Eclipse plugin.
>
> My main question is whether anyone has any suggestions on how to
> improve this hack? Why is buildContext.refresh() not enough to trigger
> a full recompilation of the .java source file?
>
> thanks
> Stephen
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