dune build @check, but only for a specific target

[ELLIOTTCABLE]

At the moment, there doesn't seem to be an idiomatic/beautiful way to build just the cmt{,i}s for a specific target.

For example, if one usually builds dune build src/api.bc for a given subproject instead of the full dune build or dune build src, I can't figure out an equivalent to dune build @src/api.bc/check or what-have-you.

I can emulate the behaviour to some extent with something like dune build src/.api.eobjs/byte/dune__exe__Api.cm{i,t,ti}, but

1. there's no variables for .cmt{,i}, so it's pretty ugly, fragile, and tied to Dune's implementation; and

2. and it doesn't seem like those can be generated for executable artifacts anyway, unless I'm mis-using them?

   opam exec --sw=../../ -- dune build '%{cmi:src/api.bc}'
   Entering directory '/home/me/code/monorepo'
   File "command line", line 1, characters 0-17:
   Error: Module Api.bc does not exist.
   make: *** [Makefile:39: check] Error 1
   

Is there a blessed path towards something like this? "Just typecheck the things that would be necessary to build ?"

[Alizter]

What you can do is define a (rule ...) which has an (alias foo) that depends on the specific file in question. That way you can write %{cmi:...} in the deps. Afterwards you can just do dune build @foo.

[emillon]

Aliases are scoped by directories, so you can do dune build @src/check and will build only the @check targets for what's in src/.

[ELLIOTTCABLE]

Unfortunately, our gigantic monorepo often has lots of fiddly, precise build-targets that share directories. 😩

[rgrinberg]

I think this should work if you use a module name: dune build '%{cmi:src/api.bc}'

So for example: dune build %{cmi:src/foo}

Although note that this doesn't type check Foo. To do that, you would need to build dune build %{cmo:src/foo}