Marquis Wang created MCOMPILER-532:
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Summary: compile doesn't work without first clean with Dagger
annotation processor
Key: MCOMPILER-532
URL: https://issues.apache.org/jira/browse/MCOMPILER-532
Project: Maven Compiler Plugin
Issue Type: Bug
Reporter: Marquis Wang
I have a reproducing example here:
https://github.com/marquiswang/incremental-compile-dagger-test. The README
there shows how it goes wrong.
Long story short, if you use mvn compile on a project with Dagger, touch the
@Injected files, then do mvn compile again, then it will not correctly compile
the Dagger-generated factory methods. You need to do a mvn clean compile.
I am pretty sure that this is because of how maven-compiler-plugin and javac
interact with Dagger.
maven-compiler-plugin will, if it detects that a file has changed, delete
compiled class files and recompile every class in the module. However, it does
not delete target/generated-sources/annotations/. It calls javac on the
Foo.java.
Dagger chooses not to re-generate the Foo_Factory.java file, presumably because
it already exists.
javac detects that no new files were created by annotation processing, so it
doesn't compile anything. According to
https://docs.oracle.com/en/java/javase/17/docs/specs/man/javac.html#annotation-processing
, javac only compiles "newly generated source files", so it doesn't compile
the existing Foo_Factory.java.
I think the solution is, when maven-compiler-plugin detects that sources have
changed it and it needs to re-compile, it should delete
target/generated-sources/annotations as well as target/classes before compiling.
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