Compiling on Ubuntu fails as a the GHC is too old to compile the latest pandoc-crossref

[tarleb]

There are three possible paths:

• Wait for upstream to release a patched version that allows compilation with older GHC versions.
• Switch to ghcup to install the compiler so we are not limited by what Ubuntu ships.
• Stop shipping pandoc-crossref as part of core and all addon images.

[cagix]

Switch to ghcup to install the compiler so we are not limited by what Ubuntu ships.

that seems like a sensible choice to me, because it allows you to use the same ghc version that pandoc itself uses, and makes you independent of the ubuntu packages.

pandoc-crossref appears to be a frequently used filter, so it would be unfortunate if it were no longer included in pandoc/extra.

[tarleb]

I agree, manually installing GHC is probably the way to go. I'm working on it.

One option would be to install GHC and cabal directly, with the other option being to install ghcup first and to proceed from there. Not sure yet which method is better in terms of simplicity, flexibility, and security.

[tarleb]

For the record: The pandoc-crossref dev stated that he won't support older GHC versions, so option (1) is out.

[cagix]

@tarleb would it be an option to build the alpine image also in arm64?

[tarleb]

Just for the record: jgm/pandoc#11155 has the discussion about alpine images on arm64.

[tarleb]

It seems there are no cabal-install packages for Ubuntu on aarch64. https://downloads.haskell.org/~cabal/cabal-install-3.16.0.0/

[tarleb]

We could simply download the pandoc-crossref binaries instead of compiling ourselves, but that's a bit of a hassle, too. It would also mean that we no longer compile against the exact pandoc version in the container, which can lead to subtle differences and bugs not being fixed.

I'm very tempted right now to remove it, but I'll give it a bit more thought.

[cagix]

would it be feasible to just use the pre-compiled pandoc binaries for the docker image instead of recompiling it? (this could also save quite a lot of ci quota?)

[tarleb]

No, because the pre-compiled pandoc binaries are statically compiled, so it's not possible to load and use Lua libraries implemented in C. Being able to install and use any Lua library is one of the main features of the Docker images. E.g., using the libyaml parser directly is as simple as running apk add lua5.4-yaml in the container, after which it can be loaded with require 'yaml'. That's all but impossible when using one of the official pandoc binaries for Linux.

[tarleb]

It wouldn't even be enough to use the latest Ubuntu instead of the LTS version that we're using right now, because even then we'd get only GHC v9.6.6. The latest pandoc-crossref needs at least GHC 9.8.1 to compile.

[tarleb]

Another option: we could stop using Ubuntu and switch to Debian.

Pros:

• Would allow us to use the official Haskell Docker images for building.
• Easy to pick a specific compiler version.

Cons:

• Very disruptive change.

[cagix]

Another option: we could stop using Ubuntu and switch to Debian.

as long as the observable behaviour does not change it should probably be fine from a user's perspective.

edit: well, for a given value of "fine". people who use this image as base image would certainly notice this chance. on the other hand, i would imagine most people just use the image as is. but who knows?

edit: so, the choices are to switch to debian to provide an arm64 image with all extras or to keep ubuntu and kick pandoc-crossref out for the foreseeable future (i.e. until the ghc version matches again)?