"active-repositories: none" reportedly broken

[gbaz]

It is reported on #8944 that this broke active-repositories: none. If so, that's very bad and we should fix it!

[ulysses4ever]

I understand MercuryTechnologies@ec242b1 fixes the problem. Should we cherry pick it?

[gbaz]

Note that this issue occurs only if there is no exising ~/.cache/cabal/packages/hackage.haskell.org -- making this less severe, because it happens on a system where no cabal update has ever been run. Once it has, then the active-repositories flag works as intended...

[geekosaur]

But that gets us back to the question of why it even matters if active-repositories: none?

[gbaz]

Indeed, the error occurs with or without active-repositories passed. Its simply that with active-repositories passed, we might hope it would disable the error.

what appears to be happening is we don't take into account active-repos when reading and validating the repo-index state.

rather, we always fetch from all the available repos. active-repos says, out of all the repos, which are "active" for solving our package set.

i'm much less certain about how bad this behavior is now, and also less certain how far we might want to go to fix it. that said, one solution would be to just turn this one specific error back into a warnning, as it is a different error than the bad index state error. rather, it reads: The package list for 'hackage.haskell.org' does not exist. Run 'cabal update' to download it.

The reason I'm ok with this being turned into a warning is if the user needed that package list to proceed (i.e. for the solver), then subsequent steps would fail anyway -- so all we've done is make the failure mode slightly faster at hte cost of making it overly general.

[gbaz]

Hrm, in fact, that's what the proposed patch PR does. It still throws in every other case -- only in the doesNotExist case does it throw MissingPackageList either as a warning or exception. So now I've come around to seeing this as the correct fix, nice.

[pwm]

It would be great to turn those errors back to warnings.

Also, if active-repositories: none is not the correct flag to instruct Cabal "don't manage my packages", then which, if any flag, is? The comment above active-repositories: none in the official docs says "Offline mode", which I always understood to be that. If we must run cabal update then, afaict, it's not offline mode.

[geekosaur]

We may have a definition problem, which that comment exacedrbates: cabal has an offline mode, but it disables all network access, it doesn't do anything to what repositories are available or how cabal uses them. (Meaning, you must update your repositories and download any dependencies before going offline, which is what most things mean by offline mode.)