Outputting generated .di files to correct module structure

[Rene Zwanenburg]

The project I'm currently working on is becoming quite large, and 
is being compiled to a few different lib files. This is useful, 
so the application and tools only have to link to the libraries 
they need.

We use DMD's interface generation option to create the header 
files, which is an awesome feature, but the problem is that it 
doesn't output interface files in the package hierarchy. For 
example, if there are two modules 
'basepackage/package1/module1.d' and 
'basepackage/package2/module2.d', the interfaces end up as 
'headers/module1.di' and 'headers/module2.di'.

Now, when we add the 'headers' directory to the include path, the 
compiler won't be able to find module1 when importing 
'basepackage/package1/module1'. It works when I simply import 
'module1', which surprises me since the interface retains the 
original module declaration.

Anyway, DMD not outputting interfaces in the package hierarchy 
makes the feature pretty much useless for large projects. Is 
there a reason for this behavior, or was this simply never 
considered? I'm willing to try and add a new switch to the 
compiler so it creates the hierarchy, but I've never touched 
DMD's source so I'm not sure if I'm the right person for the job.