[jira] (MCOMPILER-209) Incremental compilation doesn't work unless useIncrementalCompilation is set to 'false'

["Rade Martinovic (JIRA)" <ji...@codehaus.org>]

    [ https://jira.codehaus.org/browse/MCOMPILER-209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=342388#comment-342388 ] 

Rade Martinovic commented on MCOMPILER-209:
-------------------------------------------

This is quite unpleasant bug for me, it increases the overall time of compilation since I am forced to do {{clean compile}} each time I do the project build.

The workaround of setting {{useIncrementalCompilation}} to {{false}} seems to help.

> Incremental compilation doesn't work unless useIncrementalCompilation is set to 'false'
> ---------------------------------------------------------------------------------------
>
>                 Key: MCOMPILER-209
>                 URL: https://jira.codehaus.org/browse/MCOMPILER-209
>             Project: Maven Compiler Plugin
>          Issue Type: Bug
>    Affects Versions: 3.1
>            Reporter: Michael Ekstrand
>
> The compiler plugin has the [useIncrementalCompilation|https://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#useIncrementalCompilation] flag.  However, when this flag is set to {{true}} and using the {{javac}} compiler, the compilation is not very incremental; the compiler always at least claims it is rebuilding all source files (and compile times are consistent with this being what it is actually doing, though it is hard to tell).  If I set {{useIncrementalCompilation}} to {{false}}, then it actually does report that some modules are up-to-date, and some only need a subset of their files compiled.
> It seems that one  or more of the following is happening:
> * {{useIncrementalCompilation}} has some meaning that is very different from what a user would expect, actually controlling whether the compiler plugin uses some internal incremental compilation mechanism vs. incremental compilation support built-in to the particular compiler backend.  One would expect this flag to turn on incremental compilation vs. build-everything.
> * The log messages do not reflect what it is actually doing; that is, it seems possible that it's saying "Compiling 164 source files" when it's really handing 164 source files off to the compiler for potential compilation.  If this is the case, it is very confusing and misleading.
> * The logic of {{useIncrementalCompilation}} is just inverted.  Looking at the source code for the abstract compiler MOJO, it doesn't look like it's quite this simple, but I also don't know what all the various components at work are doing.
> * There is a bug in the implementation of {{useIncrementalCompilation}}.
> The result of all this is incremental compilation with Maven is very confusing and difficult to understand.



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