`cabal update` is not run?

[ulysses4ever]

• Here's a failing run (and related branch is ihere: CI: add GHC 9.6.1 cabal#8840)

Not sure if it is related to the recent events like

• Fix #29: new input cabal-update: false to skip 'cabal update' #146
• Investigate why 'cabal update' hasn't run properly when setting up GHC 8.2 and cabal 2.4 #158?

The reason may be that we first haskell/setup (which does cabal update, which for cabal-3.10 uses XDG directories for storing config, store, etc.) and then restore cache with the legacy directory structure (under ~/.cabal). This confuses cabal.

Workaround: do cache-restore before haskell/setup. maybe not: to restore, you need to know the path that we usually got as an output of the action. So, pending more investigation.

[andreasabel]

It looks like cabal update did run: https://github.com/haskell/cabal/actions/runs/4400882899/jobs/7706599146#step:4:129
Not sure what the problem is, then. Maybe two cabals installed in different locations using different homes for storing the package index?
Can you maybe equip your workflow with extra debug printing, like which cabal and the like?

[ulysses4ever]

Good idea, thank you: I'll try it. Meanwhile, Mikolaj speculated on IRC that it may be due to the XDG directory switch that cabal is making. Anyway, my experiments so far live here: haskell/cabal#8840

[Mikolaj]

I copied the speculation here: #202 (comment)

[ulysses4ever]

It looks like the suggestion to restore cached ~/.cabal before applying the haskell/setup action fixed it, so I'm closing it. Thanks all!

[Mikolaj]

Just to be certain: is the safer order of cache restore (first) vs haskell/setup/cabal update (second) the default in CI scripts generated by haskell-ci? It seems so, but perhaps there are variations or perhaps I added the cache stanza myself in my scripts I'm looking at?

[andreasabel]

@Mikolaj: Haskell CI currently does things in this order:

1. Install cabal & ghc (via ghcup or apt).
2. Write the ~/.cabal/config manually (not invoking cabal).
3. cabal update.
4. Restore ~/.cabal/store.

But then, it does not generate a CI for Windows, so might not be affected by the XDG.

I am not sure, but I thought that cabal update would only affect ~/.cabal/packages and thus be independent of ~/.cabal/store.
One would have to be more careful though if one cached the whole ~/.cabal, which I would not dare to do with my current superficial knowledge of the ~/.cabal directory structure.

[Mikolaj]

This is good news. Creating ~/.cabal early turns on our XDG backward compat mode so there's no risk of mixing up the two locations of cabal index. Thank you.

[andreasabel]

Right. Of course, ghcup might be doing something concerning the .cabal directories in step 1. there...