RFE simplify usage of patched module [by Robert Scholte, from jdk-dev]

[Alex Buckley]

On 2/25/2020 10:48 AM, Robert Scholte wrote:
> For the test sources it is unclear.
> One reason to not provide a module descriptor is because it will never 
> be a requirement for other modules.
> And what about its name, as it is actually a required module and at the 
> same also the same module.
> 
> One reason to provide a module descriptor is for the build tool to know 
> which modules are required, so it can provide the right set of modules.
> But how would such descriptor for test sources look like? Well, in the 
> end it must contain everything from the main module descriptor + the 
> test requirements.
> I assume that copy/pasting the main module descriptor for a new test 
> module descriptor + adding the extra requirements is not the preferred 
> solution.

Correct, that is no-one's preferred solution. My preferred solution (and 
I think Christian's) is for the test module's descriptor to stay 
physically independent of the main module's descriptor. Then, the build 
tool (i) FINDS the test module's descriptor and (ii) MERGES it logically 
with the main module's descriptor. Suppose the merged descriptor says 
that the main module requires org.junit -- the build tool turns that 
into an --add-modules command when compiling and running tests. Maven 
could be doing this today, helping users to focus on their white-box 
test modules rather than asking users to type obscure --add-* commands 
in the POM.

Furthermore, from what Christian has posted, the effect of merging is 
always the same anyway -- require some JUnit modules, and open the main 
module. So, in the common case, people don't even need to write a test 
module descriptor; they just need the Maven test scope to inject the 
customary --add-* commands when compiling and running code in the main 
module.

Alex