Compile time vs. runtime deps

[David Holmes]

On 11/07/2012 11:24 PM, Jaroslav Tulach wrote:
> Dne St 11. července 2012 18:33:41, David Holmes napsal(a):
>> On 11/07/2012 5:22 PM, Jaroslav Tulach wrote:
>>> Dne St 11. července 2012 08:59:20, Paul Sandoz napsal(a):
>>>> On Jul 11, 2012, at 8:28 AM, David Holmes wrote:
>>
>>> I believe both cases are possible. I can have optional dependency I need
>>> to
>>> compile against and I can as well have another optional dependency I don't
>>> need to compile against.
>>>
>>> There needs to be a way to express that properly to Jigsaw runtime as well
>>> as Javac.
>>
>> I don't see why I need to make the distinction to the compiler. I
>> declare an optional dependency and at compile-time it is, or isn't
>> found.
>
> That could produce different result during the compilation. The compilation
> could either succeed or fail. Javac and IDEs need to know whether the optional
> (in runtime) library should or should not be on the compilation "classpath".

You mean the tools are going to dynamically examine my 
module-info.java/class and use it to determine what they should set 
modulepath/classpath to ???

That is not something I would have expected at all. If I build a project 
and the optional, but needed at compile-time, module is not present then 
I get a compilation error: type XXX not found. It is then up to me to 
realize that I am missing the module that exports XXX and either install 
it to the main library or add the library it is in to the appropriate 
path. (Just as I would have to add the jar file today.)

>> During compilation I reference a type and a module for that type
>> is, or isn't, found. Whether the module was omitted or was optional it
>> is simply a compile-time error if the type is not found. (I don't expect
>> javac to know or determine that the not-found type would have been found
>> in the missing optional module - how could it?)
>
> The Javac and IDEs have to know. My proposal was to introduce some way of
> telling the system that there is a compile time only dependency. Thus for the
> case when you want a fully optional dependency you could say:
>
> requires optional m at 1.0;
>
> which would mean "m at 1.0" should not be present while compiling. Or one could
> use
>
> requires compile optional m at 1.0;
>
> which would make the "m at 1.0" optional during execution, but Javac and other
> source processing tools would know that it has to be present.

Seems like an unnecessary complication to the module system to me.

Cheers,
David



> -jt
>
>>> This is another example when runtime and compile time dependencies may
>>> differ. The first one I know is the list of annotation processor providing
>>> modules to be present when compiling, but not during execution.
>>>
>>> Time to introduce "requires compile m at 1.0"?
>>> -jt