`stack8.10.yaml`, build failure `NonEmpty` does not export `singleton`

[philderbeast]

When checking the builds with each of the stack projects, with each stack*.yaml, I see that one of them doesn't build:

$ stack build --test --no-run-tests --bench --no-run-benchmarks --stack-yaml=stack8.10.yaml
         
hledger-lib> Test running disabled by --no-run-tests flag.
hledger    > configure (lib + exe + test)
hledger    > Configuring hledger-1.33.99...
hledger    > build (lib + exe + test) with ghc-8.10.7
hledger    > Preprocessing library for hledger-1.33.99..
hledger    > Building library for hledger-1.33.99..
hledger    > [ 4 of 38] Compiling Hledger.Cli.CliOptions
hledger    >         
hledger    > /home/philderbeast/dev/src/updo/hledger-upstream/hledger/Hledger/Cli/CliOptions.hs:85:80: error:
hledger    >     Module ‘Data.List.NonEmpty’ does not export ‘singleton’
hledger    >    |    
hledger    > 85 | import qualified Data.List.NonEmpty as NE (NonEmpty, fromList, head, nonEmpty, singleton)
hledger    >    |                                                                                ^^^^^^^^^
hledger    >         
Progress 2/6         

Error: [S-7282]
       Stack failed to execute the build plan.
       
       While executing the build plan, Stack encountered the error:
       
       [S-7011]
       While building package hledger-1.33.99 (scroll up to its section to see the error) using:
       ~/.stack/setup-exe-cache/x86_64-linux/Cabal-simple_6HauvNHV_3.2.1.0_ghc-8.10.7 --verbose=1 --builddir=.stack-work/dist/x86_64-linux/ghc-8.10.7 build lib:hledger exe:hledger test:unittest --ghc-options " -fdiagnostics-color=always"
       Process exited with code: ExitFailure 1

$ git rev-parse HEAD
176a45b12a6c2c165b9f51ff8ab883d47a546a21

$ stack --version
Version 2.15.5, Git revision 5649cc6b2522f51f0fc5543154b0fff868f9af31 x86_64 hpack-0.36.0

[simonmichael]

Thanks for the report!

I see Data.List.NonEmpty.singleton was added in ghc 9.0. The cheapest fix would be to drop support for ghc 8.10. How would you feel about that ?

[simonmichael]

I have fixed it, and set up a github workflow to test with our oldest supported GHC version when needed.

[simonmichael]

Fixed it in master, that is. Preventing compilation failure for people installing hledger 1.33 from Hackage with cabal and ghc 8.10, requires a bugfix release, or waiting for the major release due next month, or adding a hackage revision on the 1.33 packages disallowing ghc 8.10 temporarily. I did the latter.