Package, import and type declarations are allowed now in module-info.java by spec

[Georgiy Rakov]

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 (§7.2
    <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