[jsr294-modularity-eg] 294 EG conf call, 2009-04-08

[Alex Buckley]

Bryan Atsatt wrote:
>> javac will enforce a match between the immediate child of ModulePath 
>> and its enclosed module-info.java/class. It is checked when compiling 
>> module-info.java and when reading module-info.class. It extends the 
>> current practice of enforcing a match between the location at which a 
>> class is found on the SourcePath/ClassPath and the fully-qualified 
>> name of that class.
> Then doesn't it follow that the version number should be "required" in 
> the directory name as well?

When multiple modules of the same name are on the filesystem at once, 
sure. When only one version of a module is present, I'm not sure 
requiring a version literal is helpful. (Maybe a version isn't just a 
number :-) Certainly it should not be mandatory to give a version when 
declaring a module in the language.

That said, let Jon and I discuss this some more.

>>> IOW, is there some lookup logic assumed here, allowing the compiler 
>>> to search for the module-info for "com.bar.app" without cracking open 
>>> the module-info files?
>>
>> In all cases I can think of, if the compiler needs the module-info for 
>> com.bar.app, then it needs to open com.bar.app/module-info. The check 
>> is somewhat auxiliary.
> Right, so the compiler can simply check all of the -modulepath entries 
> for a child directory called "com.bar.app", then expect module-info 
> under that.

Yes. I should have said that javac's regular enforcement does make this 
expectation reasonable.

> What if a user really wants to keep their existing source directory 
> structure, *and* use module-info? More compiler options (e.g. pointing 
> directly to module-info files), or "sorry"?

Oh, then you're on slide 3. Just set SourcePath/ClassPath as today and 
make sure module-info is in the root. The limitation is that you can't 
compile multiple modules in a single javac invocation. This is basically 
slides 6 and 7. To overcome that limitation, javac would have to find 
the right module-info on the SourcePath/ClassPath by either having 
module name in source or realizing which SourcePath entry (src/classes1 
v. src/classes2) encloses the file being compiled. javac would also have 
to redefine -d to allow multiple output directories, and slide 7 shows 
why that's undesirable.

Alex