java_binary: input MANIFEST file is overridden with the MANIFEST content from dependent JARs

[davido]

BUCK uses jar -cfm command to assemble the java_binary.

If the dependent JARs also contain MANIFEST.MF file then jar command mess up the content from input MANIFEST.MF and dependent JARs MANIFEST.MF files.

See that change from Gerrit project for more details:

https://gerrit-review.googlesource.com/49305

[shs96c]

I'm surprised. From the entry you link to, you say that the manifest isn't properly formed. What's the best way to repro the issue? Just run that target? Which entry in particular are you expecting to see in the manifest?

The code which generates the final jar for a java_binary can be seen here:

https://github.com/facebook/buck/blob/master/src/com/facebook/buck/java/JarDirectoryStep.java

In "createJarFile" we pass in a Manifest, which is updated (in "merge(Manifest, Manifest)") as each dependent jar is read. The final thing that happens is that we write the manifest entry to the jar. The end result is that the manifest in the generated jar should be the combined manifest.

As you can also see, the "getDescription" method takes a few liberties about how we represent this process. :)

[davido]

I created the reproducer for the issue above and detailed instructions in README file how to reproduce it:

https://github.com/davido/buck_test

[shs96c]

Ah! Now I understand. Yes, it's lame that we do that, and we should fix the behaviour.

[shs96c]

Getting a patch reviewed for this.

[davido]

Hey, cool, thanks! Can you share the patch?

[shs96c]

I've just landed it on our internal repo, and it'll be out in the next MOE push.

[shs96c]

Marking as "closed" because the code is now in a tree, and just waiting to be pushed out to Real Life.