Wrong "cabal: Encountered missing or private dependencies" error on sublibraries that start with "z"

[Mikolaj]

Describe the bug

As described under "Edit" at #5782 (comment)

Basically, the example should compile fine, just as the version listed before it that differs only in that the main library is changed to private library z, but instead it bugs out with "cabal: Encountered missing or private dependencies".

[fgaz]

Looks like a regression: #6038

But we have a test for this (#6842), why didn't it fail?

[Mikolaj]

This may be a different bug. In particular, adding an empty main (and so public) library doesn't fix compilation, unlike with the test you mention. Perhaps it's similar, but errors out not when public libraries are absent in the .cabal file, but when they are absent in the build-depends stanza (some private libraries present, but not a single public library from the same package present).

[fgaz]

looks like Setup.hs does not have this problem. only cabal-install fails.

I made a (more) minimal reproducer:

cabal-version: 2.2
name: issue5782
version: 0.1
build-type: Simple

library a
  hs-source-dirs: .
  build-depends: base
  default-language: Haskell2010

library z
  hs-source-dirs: .
  build-depends: a, base
  default-language: Haskell2010

library c
  hs-source-dirs: .
  build-depends: z, base
  default-language: Haskell2010

The weird thing is, if you rename "z" into "b"... it works.

Do stanzas have to be lexicographically ordered now?? Something must be very wrong for this to happen

[fgaz]

z

of course it's the munged package name...

workaround: don't start the name of your sublibrary with (an arbitrary number of) "z" (unless followed by something other than "z" or "-")