[Dune-devel] hacking guidance request...

[kris]

hi
when dune decides on a DAG for re-compilations stemming from a changed .ml file
(amongst a set with no .mli interfaces)
(hypothetical question) is there any provision for detecting when one
of the dependent re-compilations generates exactly the same cmi as
previously?
because I imagine, if found, that would be reason enough to terminate
further re-compilations along a particular chain of dependencies.
but this cannot happen of course because of the propagation of new CRC digests.

however, if this were a possibility (I'm working on an alternative to
the CRC digest regime and hacking in [src/dune/build_system.ml] to
switch off hygiene to allow the compiler to determine whether a
re-compilation is really needed at all) what in particular might I
look at in order to have Dune notice unchanged build artefacts and
deciding on whether to continue with a sequence of rule execution?
my hope was that the code is only trivially far away from being able
to implement this,
but I'm having difficulty following the code.
I would really appreciate some guidance as I'm stuck!