package-info

[jonathan.gibbons]

Currently, javac does not generate package-info.class when
package-info.java contains no annotations.

This can cause issues for build systems that assume that for every
*.java file, the compiler ought to generate a corresponding *.class file.

It appears that Ant 1.8 has apparently taken it upon itself to "work
around" this issue, by generating package-info.class if javac does not.
Does anyone have any opinions as to whether this is a good or bad idea?
Is this something that should really be fixed in javac, perhaps as an
optional behavior?

-- Jon

[gnu_andrew]

2009/11/3 Jonathan Gibbons <Jonathan.Gibbons@...>:

> Currently, javac does not generate package-info.class when package-info.java
> contains no annotations.
>
> This can cause issues for build systems that assume that for every *.java
> file, the compiler ought to generate a corresponding *.class file.
>
> It appears that Ant 1.8 has apparently taken it upon itself to "work around"
> this issue, by generating package-info.class if javac does not. Does anyone
> have any opinions as to whether this is a good or bad idea? Is this
> something that should really be fixed in javac, perhaps as an optional
> behavior?
>
> -- Jon
>
>
>

What would such a class contain? Presumably it would be just an empty
shell, with just a single no-argument constructor?

The package-info.java (and module-info.java) are a bit of a hack as
pseudo-Java classes to begin with, so it doesn't surprise me all that
much that another hack is needed to make them indistinguishable from
normal classes.
--
Andrew :-)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

Support Free Java!
Contribute to GNU Classpath and the OpenJDK
http://www.gnu.org/software/classpath
http://openjdk.java.net

PGP Key: 94EFD9D8 (http://subkeys.pgp.net)
Fingerprint: F8EF F1EA 401E 2E60 15FA  7927 142C 2591 94EF D9D8

[jonathan.gibbons]

Andrew John Hughes wrote:

2009/11/3 Jonathan Gibbons Jonathan.Gibbons@...:
  

Currently, javac does not generate package-info.class when package-info.java
contains no annotations.

This can cause issues for build systems that assume that for every *.java
file, the compiler ought to generate a corresponding *.class file.

It appears that Ant 1.8 has apparently taken it upon itself to "work around"
this issue, by generating package-info.class if javac does not. Does anyone
have any opinions as to whether this is a good or bad idea? Is this
something that should really be fixed in javac, perhaps as an optional
behavior?

-- Jon



    

What would such a class contain? Presumably it would be just an empty
shell, with just a single no-argument constructor?

The package-info.java (and module-info.java) are a bit of a hack as
pseudo-Java classes to begin with, so it doesn't surprise me all that
much that another hack is needed to make them indistinguishable from
normal classes.
  

Yes, it would presumably be an empty shell class.

-- Jon

[Joseph D. Darcy]

On 11/03/09 02:35 PM, Jonathan Gibbons wrote:

Andrew John Hughes wrote:

2009/11/3 Jonathan Gibbons Jonathan.Gibbons@...:
  

Currently, javac does not generate package-info.class when package-info.java
contains no annotations.

This can cause issues for build systems that assume that for every *.java
file, the compiler ought to generate a corresponding *.class file.

It appears that Ant 1.8 has apparently taken it upon itself to "work around"
this issue, by generating package-info.class if javac does not. Does anyone
have any opinions as to whether this is a good or bad idea? Is this
something that should really be fixed in javac, perhaps as an optional
behavior?

-- Jon



    

What would such a class contain? Presumably it would be just an empty
shell, with just a single no-argument constructor?

The package-info.java (and module-info.java) are a bit of a hack as
pseudo-Java classes to begin with, so it doesn't surprise me all that
much that another hack is needed to make them indistinguishable from
normal classes.
  

Yes, it would presumably be an empty shell class.

-- Jon

Yes, no constructor need be present; here is the verbose javap output from a package-info file with an annotation:

javap -verbose package-info.class
Classfile /home/darcy/Scratch/package-info.class
  Last modified Nov 3, 2009; size 109 bytes
  MD5 checksum dfc45af5b7a94a2f4bdf5c42ba29eafc
  Compiled from "package-info.java"
interface foo.package-info
  SourceFile: "package-info.java"
  minor version: 0
  major version: 51
  flags: ACC_INTERFACE, ACC_ABSTRACT, ACC_SYNTHETIC
Constant pool:
  #1 = Class              #5              //  "foo/package-info"
  #2 = Class              #6              //  java/lang/Object
  #3 = Utf8               SourceFile
  #4 = Utf8               package-info.java
  #5 = Utf8               foo/package-info
  #6 = Utf8               java/lang/Object
{
}

-Joe