Regression from 1.6 to 1.7 for libraries with archives in subdirectories

[jberdine]

I'm seeing build failures with 1.7.* that work well with 1.6.3, in particular due to bec9fbb from #1329.

I don't have a self-contained repro yet, but figured I'd open an issue in case there are any quick comments. The symptom is warnings (that a later commit makes into errors) such as:

File unavailable: /Users/jjb/.opam/sledge/lib/llvm/llvm_analysis.cmxa

This come from building a library with (libraries llvm.analysis ...) in its dune. Note that the llvm_analysis.cmxa file is actually present as /Users/jjb/.opam/sledge/lib/llvm/static/llvm_analysis.cmxa. Note the added static directory. This comes from the META.llvm file, which declares packages with archives in the static subdirectory:

name = "llvm"
version = "7.0.0svn"
description = "LLVM OCaml bindings"
archive(byte) = "static/llvm.cma"
archive(native) = "static/llvm.cmxa"
directory = "llvm"

package "analysis" (
    requires = "llvm"
    version = "7.0.0svn"
    description = "Intermediate representation analysis for LLVM"
    archive(byte) = "static/llvm_analysis.cma"
    archive(native) = "static/llvm_analysis.cmxa"
)

I don't know if META files are not supposed to do that, but it worked with dune 1.6.

FWIW, looking at the patch, the use of basename here looked suspicious to me.

[ghost]

That's definitely a bug in Dune. The basename you pointed is indeed the culprit: the same make function is used to construct Lib.t` values for both internal and external libraries and it is wrong in the case of external libraries. Thanks for debugging this.