The JLS doesn't know what the string "module-info.class" means or what a
"JAR root" is. It only knows about Unicode input matching the
CompilationUnit production. Nothing is mandated about the filesystem
layout of files containing CompilationUnit productions that include a
PackageDeclaration. For clarity, we could extend 7.6's compiler guidance
to cover a file called module-info.java, but technically the guidance is
already broad enough to allow a compiler to "do the right thing".
Alex
On 3/14/2016 9:08 AM, Paul Benedict wrote:
Alex, you wrote: "The JLS doesn't prevent javac from rejecting a package
declaration or an import declaration in a file called module-info.java."
It seems that a package declaration, in this context, should be
prohibited syntax because module-info.class is always in the JAR root
which has no package.
Cheers,
Paul
On Wed, Mar 9, 2016 at 4:02 PM, Alex Buckley <alex.buck...@oracle.com
<mailto:alex.buck...@oracle.com>> wrote:
The JLS doesn't prevent javac from rejecting a package declaration
or an import declaration in a file called module-info.java.
In fact, since a package declaration or import declaration must be
followed by a type declaration, and since a type declaration cannot
use a hyphen, javac is free to take the optional rule from JLS 7.6
-- filename must align with type declaration -- and develop it
further: rejecting a package declaration or import declaration in
module-info.java because the filename cannot possibly align with any
type declaration.
I can't speak to what a particular EA build of javac is doing with a
particular option. javac options are irrelevant to the JLS. If a
compiler accepts the Java language circa SE 9, then a module
declaration is a valid compilation unit. What's the name of the file
containing such a compilation unit? Anything the compiler likes.
Alex
On 3/9/2016 5:14 AM, Georgiy Rakov wrote:
Hi Alex,
if I understand correctly you mean about following assertions
from JLS 7.6:
If and only if packages are stored in a file system (ยง7.2
<http://docs.oracle.com/javase/specs/jls/se8/html/jls-7.html#jls-7.2>),
the host system may choose to enforce the restriction that
it is a
compile-time error if a type is not found in a file under a
name
composed of the type name plus an extension (such as |.java|or
|.jav|) if either of the following is true:
*
The type is referred to by code in other compilation
units of
the package in which the type is declared.
*
The type is declared |public|(and therefore is potentially
accessible from code in other packages).
Literally these assertion doesn't make presented behavior
corresponding
to spec because the declared type is neither public nor being
referred
to from other sources being compiled.
Nevertheless following sources doesn't compile either despite
the fact
that no types are declared there at all.
Namely when only package is specified:
mod\module-info.java:
module mod {
exports pkg;
}
mod\pkg\module-info.java:
package pkg;
then compiling it by following command line with javac from [2]:
javac -modulesourcepath . mod\module-info.java
mod\pkg\module-info.java
causes following output:
mod\pkg\module-info.java:1: error: expected 'module
package pkg;
^
1 error
When only import statment is specified:
mod\module-info.java:
module mod {
exports pkg;
}
mod\pkg\module-info.java:
import java.util.List;
then compiling it by following command line with javac from [2]:
javac -modulesourcepath . mod\module-info.java
mod\pkg\module-info.java
causes following output:
mod\pkg\module-info.java:1: error: expected 'module'
import java.util.List;
^
1 error
Please see minimized test cases attached in tests23.zip. In order to
reproduce, please:
1. Unzip the attached archive to some dir on Windows machined, say
directory A;
2. Rename A\test2\test_bat to A\test2\test.bat and
A\test3\test_bat to
A\test3\test.bat;
3. Modify these two test.bat files by changing JDK_HOME variable to
point to your jigsaw JDK 9 installation directory;
4. Run test.bat files in turn.
BTW: javac behavior [2] currently differs depending on whether
sources
are compiled "in module" mode or not. By "module mode" I mean
specifying
modulesourcepath option. For instance without modulesourcepath
option
module declarations are not recognized as valid grammar while import
declarations contained within module-info.java compile successfully.
This can be seen by experimenting with test3 from the attached
testcases. Now javac from [2] even can throw exception in
"non-module"
mode, please see https://bugs.openjdk.java.net/browse/JDK-8150733.
Could you please tell if spec will specify somehow two modes of
processing java-sources, now it [1] doesn't.
[1] http://cr.openjdk.java.net/~mr/jigsaw/spec/lang-vm.html
[2]
http://download.java.net/java/jigsaw/archive/106/binaries/jigsaw-jdk-9-ea+106_windows-x86_bin.zip
Thanks,
Georgiy.
On 26.02.2016 21:26, Alex Buckley wrote:
On 2/26/2016 8:37 AM, Georgiy Rakov wrote:
current spec [1] now contains following assertions
related to grammar:
A compilation unit (JLS 7.3) may contain a module
declaration, in
which case the filename of the compilation unit is
typically
|module-info.java|.
CompilationUnit:
[PackageDeclaration] {ImportDeclaration}
{TypeDeclaration}
ModuleDeclaration
These assertions allows to specify any of import,
package or type
declarations in any compilation unit, for instance
module-info.java is
allowed to contain any of the mentioned declarations.
However currently
javac in the latest jigsaw build [2] reports an error on
such cases
provided they are compiled in module mode. For example
if we have
following directory structure:
mod\module-info.java:
module mod {
exports pkg;
}
mod\pkg\module-info.java:
package pkg;
class C {
}
then compiling it by following command line with javac
from [2]:
javac -modulesourcepath . mod\module-info.java
mod\pkg\module-info.java
causes following output:
mod\pkg\module-info.java:1: error: expected 'module'
package pkg;
^
1 error
javac is merely choosing to implement the rule at the end of
JLS 7.6
that a type declaration (optionally preceded by package/import
declarations) must be provided in a suitably named file.
Perhaps I should say "a variant of the rule" because 7.6 as
written
concerns a public type and your example has a package-access
type.
Still, bottom line, javac is free to require that a
compilation unit
which starts with a package declaration _must not_ be in a
file called
foo-bar.java -- the hyphen indicates a name that can't
possibly align
with the type declared in the compilation unit.
The error message for mod\pkg\module-info.java could be a
bit more
helpful, but that's a quality-of-implementation detail.
Conversely, a compilation unit that contains a module
declaration
_may_ be in a file called module-info.java, or in a file called
foo-bar.java, or in a file called mod_decl.JAV. The
"typically" in [1]
is meant to indicate that the sub-clause on filename is
non-normative.
This is akin to how a compilation unit that contains a
package-access
type declaration for class C _may_ be in a file D.java.
Alex
