hpack on wrong version yet `stack build` does not fail

[xave]

General summary/comments (optional)

Steps to reproduce

For example:

1. hpack on wrong version
2. run stack build ... --file-watch
3. get message stating

foo.cabal was generated with a newer version of hpack,
please upgrade and try again.

Success! Waiting for next file change

For reference, the code to be compiled included an obviously malformed line that should have triggered an error, yet a Success! was output:

qehww = ::

Expected

Stack build fails if hpack is not correct

Actual

Stack version

stack --version
Version 2.9.1, Git revision 13c9c8772a6dce093dbeacc08bb5877bdb6cfc2e (dirty) (155 commits) aarch64

Method of installation

• Via GHCup

Platform

macOS M1 v 12.6.3

[mpilgrem]

@xave, thanks for reporting. Hpack does not over-write an existing Cabal file, if it was generated by a more recent version of Hpack. Pantry (on which Stack depends), when it is using its built-in version of Hpack, warns when this occurs but does not consider it fatal - it will go on to use the existing Cabal file that was not over-written.

I assume that, in this case, the Haskell error (qehww = ::) was in a Haskell source file not built given the package description in the existing Cabal file.

If you want to prefer the package.yaml package description over the existing Cabal file, you need to delete the existing Cabal file.

[xave]

I think the message would be more helpful if it said to delete the file based on one's preference. It is not intuitive that the tools says a build is successful when there is an obvious error in a file.

[xave]

I eventually realized to delete the file.

[xave]

Thanks!

[pbrisbin]

@mpilgrem we just ran into this again, so I'd like to re-iterate the feature request: I would very much like a way (if not the default) to make this a fatal error.

Hpack does not over-write an existing Cabal file, if it was generated by a more recent version of Hpack. Pantry (on which Stack depends), when it is using its built-in version of Hpack, warns when this occurs but does not consider it fatal - it will go on to use the existing Cabal file that was not over-written

Are you implying we should report this on Pantry and not Stack?

For context, we have release automation that runs stack build --dry-run on CI. Because CI and local developer versions may differ, there's a risk of this scenario happening. And if it does, we would silently ship an out of date .cabal file. We'd very much like it to fail the release instead.

[chris-martin]

A way to disable the hpack version check altogether would also suffice. I have no idea why I would ever care what version of hpack was previously used to generate the existing cabal file, since the new execution of hpack is going to entirely overwrite its contents anyway.

[mpilgrem]

@chris-martin, I think you are seeking Stack's existing --hpack-force flag, see:

• https://docs.haskellstack.org/en/stable/configure/global_flags/#-no-hpack-force-flag