Ambiguous TargetSelector crash

[lukel97]

Describe the bug
In the project haskell-language-server, calling cabal repl exe/Arguments.hs from the root directory will give this error:

$ cabal repl exe/Arguments.hs 
TargetSelector: internal error: NoMatch
CallStack (from HasCallStack):
  error, called at ./Distribution/Client/TargetSelector.hs:669:3 in main:Distribution.Client.TargetSelector

This is because a subproject ghcide which is included in the packages field of cabal.project also has a module in a folder ghcide/exe/Arguments.hs.
This doesn't happen when calling cabal repl exe/Arguments.hs from inside ghcide.

Steps to reproduce
Working on getting a minimal test case

Expected behavior
Presumably in this scenario, cabal repl src/Arguments.hs should resolve to the src/Arguments.hs in the root project.

System information

• cabal HEAD

[lukel97]

Turns out this is actually caused because there are two executables that build the same module, which in this case is indeed actually ambiguous. However it looks like the error is getting mangled and an internal one is thrown instead whenever the modules are located within a hs-source-dirs.

$ tree
.
├── cabal-ambig-sel.cabal
└── src
    └── F.hs

1 directory, 2 files
$ cat cabal-ambig-sel.cabal 
cabal-version:       >=1.10
-- Initial package description 'cabal-ambig-sel.cabal' generated by 'cabal
-- init'.  For further documentation, see
name:                cabal-ambig-sel
version:             0.1.0.0

executable A
  main-is: Main.hs
  hs-source-dirs: src
  other-modules: F

executable B
  main-is: Main.hs
  hs-source-dirs: src
  other-modules: F

In this test case, removing the hs-source-dirs and placing F.hs in the root produces the proper error

$ cabal repl F.hs
cabal: Ambiguous target 'F.hs'. It could be:
:pkg:cabal-ambig-sel:exe:A:file:F (file)
:pkg:cabal-ambig-sel:exe:B:file:F (file)

cabal-ambig-sel.tar.gz

[phadej]

Have you tried with current master. There were patches improving how target selection for files behave.

[lukel97]

Yeah this is happening with 07c1a43
I've been poking through TargetSelector.hs and I'm still trying to wrap my head around what is making this an internal error, rather than a genuine ambiguous selector error

[phadej]

Write a test case :)

[lukel97]

PR created for fix. The reason why this was working with the case where there was no hs-source-dir was by coincidence --- since files Foo.hs are rendered as Foo, this just happened to match the module syntax.