[SPARK-21592][BUILD] Skip maven-compiler-plugin main and test compilations in Maven build

[gslowikowski]

scala-maven-plugin in incremental mode compiles Scala and Java classes. There is no need to execute maven-compiler-plugin goals to compile (in fact recompile) Java.

This change reduces compilation time (over 10% on my machine).

[srowen]

I think you may be right. However if so you can remove the configuration of maven-compiler-plugin in the two submodules that further refine the config.

[gslowikowski]

Yes, I forgot about it.

[srowen]

Why is this necessary/OK?

[gslowikowski]

Changing phase to one before compile is very old trick, used when scala-maven-plugin compiles only Scala classes and this compilation must be performed before Java classes compilation (by maven-compiler-plugin) because Java classes depend on Scala classes.
In incremental compilation mode SBT compiler is used internally and it compiles everything. Because maven-compiler-plugin is disabled (compilations are skipped), there is no need to change default phase.

[gslowikowski]

Do you want me to update pull?

[srowen]

Yeah then I can run tests

[gslowikowski]

Updated.

BTW Travis build fails on the last phase - dev/lint-java script.

[srowen]

Likewise @vanzin any thoughts on this one? because it touches the compilation and build

[srowen]

This will need a JIRA @gslowikowski , by the way

[SparkQA]

Test build #3861 has finished for PR 18750 at commit d9dfe3a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

@gslowikowski I'll merge this if you'll make a JIRA and link it here via the title

[gslowikowski]

Created https://issues.apache.org/jira/browse/SPARK-21592

[srowen]

Looks good @gslowikowski , just put [SPARK-21592] at the start of the title to link them.

[srowen]

Merged to master. I'll watch the builds to make sure it's really happy with this change.