cannot include 5.0.1 in stack project

[ndwarshuis]

I might be missing something very basic about how cabal works, but I cannot use 5.0.1 in a stack project without getting this error:

Error: While constructing the build plan, the following exceptions were encountered:                                                                                                           
                                                                                                                                                                                               
In the dependencies for mybin-0.1.0.0:                                                                                                                                                        
    persistent-mtl is a library dependency, but the package provides no library                                                                                                                
needed since budget is a build target.                                                                                                                                                         

stack file:

resolver: lts-20.9

extra-deps:
- persistent-mtl-0.5.0.1@sha256:44e14fdf2906676e8d40262ab1a4da6d22f766d4b6140be7321f662c05fb0ae2,3011
# other stuff...

package.yaml

name: mybin
# version/repo stuff...

dependencies:
- persistent-mtl >= 0.5.0.1
# other deps

library:
  source-dirs: lib/
  ghc-options:
  - -Wall
  - -Wcompat
  - -Widentities
  - -Wincomplete-record-updates
  - -Wincomplete-uni-patterns
  - -Wredundant-constraints
  - -Wpartial-fields
  - -Werror
  - -O2

executables:
  mybin:
    main:                Main.hs
    source-dirs:         app
    ghc-options:
    - -Wall
    - -Wcompat
    - -Widentities
    - -Wincomplete-record-updates
    - -Wincomplete-uni-patterns
    - -Wredundant-constraints
    - -Wpartial-fields
    - -Werror
    - -O2
    - -threaded
    dependencies:
    - mybin

Downgrading to 5.0.0 works, which makes me wonder if it has to do with the buildable: False directive in the persistent-mtl .cabel file.

[brandonchinn178]

Yes, GHC 9.2 has a bug that breaks persistent-mtl: #45

5.0 might build, but it'll probably fail at runtime

[ndwarshuis]

thanks for clarifying, does this just affect 5.0.1 or all of 5.0.x? (eg do I need to drop down further to 4.x if I want to stick with ghc 9.2?)

[brandonchinn178]

Unfortunately, the MonadSqlQuery (TransactionM m) constraint is the thing causing issues, which was added in 4.0. So you'd need to drop to 3.0. I guess theoretically we could avoid adding the constraint in GHC 9.2, which would allow general use of the library to work with GHC 9.2, but using functions polymorphically wouldn't typecheck.

If you want to tinker around and put up a PR, I could merge it! I won't be able to try anything this weekend.