mega-repo handling

[ivan-m]

General summary/comments (optional)

The current behaviour is that (from the manual):

A location key can be accompanied by a subdirs key to look for cabal files in a list of subdirectories as well in addition to the top level directory.

However, mega-repos that have a package in the top-level directory as well as in sub-directories don't seem to allow those sub-directories to depend on the top-level directory.

Example repositories: fgl (which I maintain) and servant-auth-token.

Steps to reproduce

I'm going to use the fgl repository here as an example (with both fgl and fgl-arbitrary in my build-depends).

In this commit, there is a bump both to the top-level fgl package and the fgl-arbitrary package, which I'm going to try and use:

resolver: lts-8.8
packages:
- '.'
- location:
    git: git@github.com:haskell/fgl
    commit: 12b14b3f30096c9cddc3b93dbee88a3921a3ad55
  subdirs:
    - fgl-arbitrary
  extra-dep: true

I'm going to be running stack install --only-dependencies on this.

Expected

The package in the sub-directory should depend on the package in the root directory.

Actual

$ stack install --only-dependencies

Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for fgl-arbitrary-0.2.0.3.1:
    fgl-5.5.3.1 must match >=5.5.3.1.1 && <6
needed due to my-package-0.1 -> fgl-arbitrary-0.2.0.3.1

Stack version

$ stack --version
Version 1.4.0 x86_64 hpack-0.17.0

Method of installation

• Updated/built using previous version of stack

[ivan-m]

(Note: this even occurs if I try and use fgl-arbitrary from Stackage/Hackage and just fgl from the repository, so it seems that the git-based packages aren't taken into account when constructing the build plan.)

[ivan-m]

It appears that the solution is to explicitly add '.' in to the subdirs list.