Convenience in the Haskell ecosystem

158

I did a big collection of those somewhere on r/haskell a year ago or so, got some karma, but the trail of tears went on anyway.

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159

And this is exactly why cabal install delenda* est.

We can put it back when its handling is fixed. Before that - let it be known that we made a big screw up here and keep people away. “Crime scene, do not cross.”

* By replacing its handler with the notice herding users to a good project management tutorial.

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160

I noticed the new Learn Physics with FP (Haskell) (Walck, December 2022) liberally suggests cabal install and cabal install --lib. And, I thought: ‘oh, maybe that’s ok now, or at least with this.’

Spoiler? It’s not.

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161

Out of curiosity, how did cabal install / cabal install --lib blow up with LPWFP?

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162

I just want to chip in because I ran into 1 more example.

I find that I spend more time fighting certain things which I’ve never had to think much about in other language ecosystems.

Specifically how to run a specific test. I leave a codebase for a few months, and I have to remember this again, which usually means googling around, and some old stackover pages.

But I think things like running a test and running a specific test should not be something you spend considerable time figuring out.

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163

Yeah this can be improved. For instance, if I pass --help to my tasty test suite with

cabal test --test-options='--help'

I get no help. Now, it is in the log file that for printed. Because --help prints to stdout.

The help itself answers the question of how to run specific tests at least.

This is technically cabal’s fault, but at the same time, suppressing stdout for tests that exit 0 is a sensible default. Maybe it’s on tasty to output help to stderr and defy convention? I’m not sure.

164

You can

cabal run tests -- --help

and it works fine.

165

So, it’s 100% possible I’m doing something to screw this up, and if so: my apologies, and hurray for learning something new.

The following is the process outlined in the appendix. He first offers global lib instructions, then this for local. Similar sort of thing, really, just changes where the config file gets stored. He recommends renaming the config file and installing all the libraries you’re interested in at once if you want more than one. The example he gives for that is: cabal install --lib gnuplot gloss cyclotomic --package-env . for local, cabal install --lib gnuplot gloss cyclotomic for global. (See page 585 of the print edition.)

andrew@ajf-mbp temp % ghci
GHCi, version 9.6.3: https://www.haskell.org/ghc/  :? for help
ghci> 2 + 2
4
ghci> :q
Leaving GHCi.
andrew@ajf-mbp temp % cabal install --lib gnuplot --package-env .
Resolving dependencies...
andrew@ajf-mbp temp % ghci
Loaded package environment from /Users/andrew/dev/temp/.ghc.environment.aarch64-darwin-9.6.3
GHCi, version 9.6.3: https://www.haskell.org/ghc/  :? for help
ghci> :m Graphics.Gnuplot.Simple
ghci> :t plotFunc
plotFunc
  :: (Graphics.Gnuplot.Value.Atom.C a,
      Graphics.Gnuplot.Value.Tuple.C a) =>
     [Attribute] -> [a] -> (a -> a) -> ghc-prim:GHC.Types.IO ()
ghci> 2 + 2

<interactive>:3:3: error: [GHC-88464]
    Variable not in scope: (+) :: t0 -> t1 -> t
ghci> :q
Leaving GHCi.
andrew@ajf-mbp temp % cat .ghc.environment.aarch64-darwin-9.6.3
clear-package-db
global-package-db
package-db /Users/andrew/.cabal/store/ghc-9.6.3/package.db
package-id gnplt-0.5.7-1f7a223d

So, base doesn’t get loaded, which is easy enough to fix. But, I feel like that’s something you don’t really want to expose a complete beginner to. I’m a bit puzzled as to what the author thought ought to happen here, which is why I’m assuming I’m doing something dumb myself. :slight_smile:

-e- It was the very first post in this thread that prompted me to go look up what LPWFP suggested.

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166

This is a very important common use case that i added to [Initiative] Improve Cabal documentation structure to become more beginner-friendly · Issue #9214 · haskell/cabal · GitHub to write a Cabal guide for (testing setup and running in general).

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167

This was a bug in the last version of cabal which is going to be fixed with the coming release.

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168

Really? That’s good to know. Thanks. Although, I would have sworn this was what happened the last time I ventured into install --lib territory over a year ago.

Cool, ta!

169

Challenge accepted :slight_smile: I spent in total 2.5 hours this evening writing GitHub - Bodigrim/cabal-add: Extend Cabal build-depends from the command line. Would you like to try and break it?

$ cabal-add --help
Usage: cabal-add [-f|--cabal-file FILE] [-c|--component ARG] DEP

  Extend build-depends from the command line

Available options:
  -f,--cabal-file FILE     Cabal file to edit in place (.cabal file in the
                           current folder, if omitted)
  -c,--component ARG       Package component to update (the main library, if
                           omitted)
  DEP                      Package to add to build-depends section
  -h,--help                Show this help text
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170

Thanks very much! When I have time, I will try my best to do so…

(That being said, I’m very busy writing my thesis right now, so I might not get to it soon. This is also why the templating tool I promised earlier isn’t ready yet.)

171

Ah this is amazing! I will try this out tomorrow and report any issues if I find anything. Thanks Bodigrim!

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