Thanks Oleg

my first guess is that: when working on the unsaturated type families paper, you did `cabal install --lib report`; or something similar. `report` is probably some internal library to that paper / project.

I am confident I did nothing like that.  But there is a file called report.cabal in the directory where I did the ‘cabal install lhs2tex’ command.

To confirm, check what is in your ~/.ghc/x86_64-linux-8.6.5/environments/default (or similar), is some `package-id report-0.1.0.0-hexhash` line there?

There is no such file:

bash$ ls ~/.ghc

ghci_history        x86_64-linux-8.9.0.20190414  x86_64-linux-8.9.0.20190508

x86_64-linux-8.6.4  x86_64-linux-8.9.0.20190430  x86_64-linux-8.9.0.20190527

bash$ ls ~/.ghc/x86_64-linux-8.6.4/

package.conf.d

Simon

From: Oleg Grenrus <oleg.grenrus@iki.fi>
Sent: 30 May 2019 20:19
To: Simon Peyton Jones <simonpj@microsoft.com>; cabal-devel@haskell.org
Subject: Re: Cabal install

Hi Simon,

my first guess is that: when working on the unsaturated type families paper, you did `cabal install --lib report`; or something similar. `report` is probably some internal library to that paper / project.

In that case, you are hitting the unfortunate cabal bug [1].

To confirm, check what is in your ~/.ghc/x86_64-linux-8.6.5/environments/default (or similar), is some `package-id report-0.1.0.0-hexhash` line there? If so, the simplest fix is to remove that environment file.

- [1] https://github.com/haskell/cabal/issues/5888 https://github.com/haskell/cabal/issues/5559

Cheers,
Oleg

On 30.5.2019 16.50, Simon Peyton Jones wrote:

Dear friendly Cabal folk

Here’s what happened to me today

bash$ cabal install lhs2tex

cabal: Could not resolve dependencies:

[__0] next goal: report (user goal)

[__0] rejecting: report-0.1.0.0 (conflict: requires UnsaturatedTypeFamilies)

[__0] fail (backjumping, conflict set: report)

After searching the rest of the dependency tree exhaustively, these were the

goals I've had most trouble fulfilling: report

Crumbs.  What is ‘report’?  Why does it need UnsaturatedTypeFamilies?   I’m totally lost.

Then, in an inspired moment, I thought to change to a different directory, ~/tmp. 

Then quite different things happened – it downloaded and built relevant libraries.

I think that there just happened to be a .cabal file in the original directory I was in at the time.  That appears to affect what ‘cabal install’ does in a truly radical way.

My point is this: this is terribly confusing for the user (at least for this on).   I’d be shocked if ‘apt install blah’ behaved utterly differently in different directories.  I’m going to make a little empty directory somewhere, and cd to it before invoking cabal in future.  But that just feels like a workaround, not a solution.

I’m not saying it’s wrong – just giving you a data point that it had one user completely stumped

Simon

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