Mysterious user goal dependency added

[JosephLucas]

On NixOS, running cabal build tries to resolve a mysterious dependency (user goal) from a previous project.

To Reproduce

(with probably a local state somewhere : not ~/.{ghc,cabal,ghci}

mkdir new-project
cd new-project
cabal init
cabal build

I get

Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: B-0.0.0 (user goal)
[__1] unknown package: p1 (dependency of B)
[__1] fail (backjumping, conflict set: B, p1)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: B, p1

B and p1 are previous package/libraries that I built successfully in another multi-project

Expected behavior
I do not expect B and p1 here, since they are not in the current project dependencies.

System information

• NixOS
• cabal version 3.4.0.0, ghc ersion 8.8.4

---

FIX:

Adding a cabal.project file with

optional-packages:
  *
write-ghc-environment-files: never

Fixes the issue. The issue may thus be caused by ghc-environment-files written by cabal run.

[fgaz]

Could there be a cabal.project or cabal.project.* file in an upper directory? The environment file shouldn't have an effect