Cabal install

[Oleg Grenrus]

Hi Simon,

I see, you triggered another feature/bug of cabal install, namely when 
you are in a project directory, project settings affect solving process. 
And when there's a .cabal file, it's a project.
So cabal tried to find an install plan containing local packages (that 
makes sense, if you try to install local lhs2tex for example!)

Solution is to change directory (cd) somewhere else and try again. 
(There's also cabal install -z flag feature request, -z to ignore local 
project; but it's not yet merged).

- Oleg

On 31.5.2019 11.02, Simon Peyton Jones wrote:
>
> 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 at iki.fi>
> *Sent:* 30 May 2019 20:19
> *To:* Simon Peyton Jones <simonpj at microsoft.com>; cabal-devel at 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://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fhaskell%2Fcabal%2Fissues%2F5888&data=02%7C01%7Csimonpj%40microsoft.com%7C5a4d4dc3dc214b29d8f408d6e533b91b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636948407671672464&sdata=OH3R%2Fl9xP6d2w8OUQ8V%2FUa%2Bp%2FEpDeqyy%2FWWBxTJ7Q%2BQ%3D&reserved=0>https://github.com/haskell/cabal/issues/5559
> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fhaskell%2Fcabal%2Fissues%2F5559&data=02%7C01%7Csimonpj%40microsoft.com%7C5a4d4dc3dc214b29d8f408d6e533b91b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636948407671682461&sdata=%2Fo%2FL6ZWU%2Bt2fA1CDGqjHL7RU1FFHGbIJacPzLNctZyE%3D&reserved=0>
>
> 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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