[jira] [Created] (HADOOP-12761) incremental maven build is not really incremental

["Sangjin Lee (JIRA)" <ji...@apache.org>]

Sangjin Lee created HADOOP-12761:
------------------------------------

             Summary: incremental maven build is not really incremental
                 Key: HADOOP-12761
                 URL: https://issues.apache.org/jira/browse/HADOOP-12761
             Project: Hadoop Common
          Issue Type: Bug
          Components: build
    Affects Versions: 2.7.2
            Reporter: Sangjin Lee
            Assignee: Sangjin Lee
            Priority: Minor


For any version that uses v.3.1 of the maven-compiler-plugin, the incremental maven build is basically broken. For most of the modules, an incremental build ({{mvn install -DskipTests}} on an already built directory for example) rebuilds the whole module again:

{noformat}
[INFO] ------------------------------------------------------------------------
[INFO] Building Apache Hadoop Common 3.0.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-antrun-plugin:1.7:run (create-testdirs) @ hadoop-common ---
[INFO] Executing tasks

main:
[INFO] Executed tasks
[INFO] 
[INFO] --- hadoop-maven-plugins:3.0.0-SNAPSHOT:protoc (compile-protoc) @ hadoop-common ---
[INFO] No changes detected in protoc files, skipping generation.
[INFO] 
[INFO] --- hadoop-maven-plugins:3.0.0-SNAPSHOT:version-info (version-info) @ hadoop-common ---
[WARNING] [svn, info] failed with error code 1
[INFO] SCM: GIT
[INFO] Computed MD5: c8e92ce138fcd723204649e4d7c6ddd
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ hadoop-common ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 7 resources
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ hadoop-common ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 871 source files to /Users/foo/hadoop/hadoop-common-project/hadoop-common/target/classes
{noformat}

It turns out that the incremental build feature of the maven compiler plugin is basically broken at v3.1 (see http://stackoverflow.com/questions/17944108/maven-compiler-plugin-always-detecting-a-set-of-sources-as-stale and MCOMPILER-209). Ironically, this can be fixed by turning off the "incremental build" configuration of the plugin.



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