Avoid generated-sources clash with MapStruct in codegen

[famod]

Fixes #11253

This avoids recreation attempts of annotation processors like MapStruct that are writing to ${project.build.directory}/generated-sources/annotations by default.
See also: http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#generatedSourcesDirectory

The additon of ${project.build.directory}/generated-sources by CodeGenMojo seems to make MapStruct (or any other processor) see its own output a second time. This change is preventing this by introducing a disjunct subdirectory.

[famod]

FTR, there is an alternate approach: #11311

[gastaldi]

LGTM

[famod]

@michalszynkiewicz it would be great if you could have a look at this.

Btw, this PR does not change the unconditional execution of the prepare goal by the dev goal.
I suggest to rethink that. Dev mode might be fast to start in small projects, but it definitely takes its time in larger, multi-module projects which is why any overhead should be avoided, IMHO.

[famod]

formatter-maven-plugin seems a bit overzealous at times...

[gastaldi]

Not directly related, but it seems that MapStruct should also generate sources in a disjunct subdirectory, avoiding using the generated-sources directory directly

[famod]

@gastaldi It is implicitly using generated-sources/annotations (the default) which should be ok for annotation processors.

[gsmet]

Let's wait for @aloubyansky and @michalszynkiewicz 's approvals before merging this one.

[gsmet]

@famod please don't set older versions. I do it when backporting. Until then it must target master and have the triage/backport? label.

[famod]

@gsmet Ok, will do. I actually had a look at the new COMMITTERS.md and was still a bit unsure after that.

[michalszynkiewicz]

I think the proper fix may be to remove the following line instead, checking it

quarkus/devtools/maven/src/main/java/io/quarkus/maven/CodeGenMojo.java

Line 109 in bbb79f1

sourceRegistrar.accept(generatedSourcesDir);

[michalszynkiewicz]

PR for ^ #11328

[famod]

FTR, I left a comment at #11328. Summary: A dedicated subdirectory still seems like the cleanest solution, IHMO.

[famod]

With #11328 now merged, this PR has become optional. If we want to make extra sure to avoid clashes it can be merged, otherwise it should be closed.

[michalszynkiewicz]

On one hand, we are even more separate with changing generated-sources to sth else here, on the other, subdirectories of generated-sources seem to be the standard location for generated sources ;)

[michalszynkiewicz]

@aloubyansky WDYT?

[aloubyansky]

I think it makes sense. If you execute package, both test and app sources are generated, right? if they are in the same location, will all of them end up being packaged?

[michalszynkiewicz]

What we have now in master puts the "normal" generated sources in the tartget/generated-sources dir and the test ones in target/generated-test-sources

The test mojo adds stuff as test compile source root: https://github.com/quarkusio/quarkus/blob/master/devtools/maven/src/main/java/io/quarkus/maven/CodeGenTestMojo.java#L18

While the normal one adds it as a compile source root: https://github.com/quarkusio/quarkus/blob/master/devtools/maven/src/main/java/io/quarkus/maven/CodeGenMojo.java#L62

I don't think the test classes would sneak into user's app.

This PR shouldn't change this behavior

[aloubyansky]

Then it's your call @michalszynkiewicz

[michalszynkiewicz]

@famod I will close this PR, we can resurrect it if we have problems in the future.
Thanks a lot for your work on it, it sped up finding the unnecessary sources registration fixed in #11253

[famod]

Glad I could help!