Fwd: Re: Modules with packages duplication

[Georgiy Rakov]

Hello Jon,

we've encountered situation when class files resulted from successful 
compilation cause runtime error; the sources are compiled by single 
javac invocation. This looks like incorrect javac behavior, namely it 
seems that javac should produce compile-time error if one tries to 
compile sources which will cause error at runtime. Could you please 
confirm if it's really is.

More details are provided in the forwarded message below. I have also 
attached an archive with minimized testcase and scripts to run it. In 
order to run it please:

1. Unzip attached archive to some machine (Windows or Unix);

2. If it's Windows rename test18/test_bat to test18/test.bat.

3. Modify JDK_HOME variable inside test18/test.bat (or test18/test.sh) 
to point to your JDK installation.

4. Run test18/test.bat (or test18/test.sh).

Thank you,

Georgiy.



-------- Forwarded Message --------
Subject: 	Re: Modules with packages duplication
Date: 	Thu, 05 May 2016 18:21:20 +0300
From: 	Konstantin Barzilovich <konstantin.barzilovich at oracle.com>
Organization: 	Oracle Corporation
To: 	ML OpenJDK Jigsaw Developers <jigsaw-dev at openjdk.java.net>, Alan 
Bateman <Alan.Bateman at oracle.com>



Hello Alan,

Thank you for the answer.

I have one more question connected with duplication of packages.
Now we can compile two modules with the duplicated package without compile-time error if there is no module which can access both of them.
But in case of these two modules are readable by third module, in runtime it will result in error of boot Layer, as you said.
Is it okey, that compiler allow us to compile code, that will cause runtime failure?

Here is minimal test case:
------------------------------
module1/module-info.java
module module1 {
      exports pack;
}

module1/pack/A.java:
package pack;
public class A{}

module2/module-info.java
module module2 {
}

module2/pack/A.java:
package pack;
public class A{}

module3/module-info.java:
module module3{
      requires module1;
      requires module2;
}

Thanks,
Konstantin.

>
> On 04/05/2016 14:18, Konstantin Barzilovich wrote:
>> Hello,
>>
>> I can see that RI checks if there are packages with the same names in >> different modules (named or unnamed).
>> This check fails even if there is no clash (no module can read both >> packages).
>> Will it be the same in final version of JDK9 or it can be changed soon?
>>
> I think you are asking about modules on the application module path > (`java -modulepath ...`) that are resolved at startup. These are defined > to the application class loader so they cannot have overlapping > packages. It's trivial to do things like map each module in its own > class loader but that messes with visibility with lots of implications > (particularly when running with both a class path and module path or > where you bringing automatic modules into the picture). So what you are > seeing is specific to the boot Layer and no specific short term plans to > change this.
>
> -Alan