Yesod and cabal hell | Mathematics and Machines

haskell cabal

Today I decided to have a go at installing Yesod for the first time. I already had the Haskell Platform installed, so according to the tutorial I was supposed to run

cabal update
cabal install yesod yesod-bin cabal-dev

and be on my merry way. Unfortunately, instead of having a functional Yesod installation I had instant Cabal hell. Doing yesod init set up the scaffolding fine, and it recommended a cabal sandbox init so I did that, but then yesod devel fed back messages like these:

Configuring yesod-test-0.0.0...
cabal: At least the following dependencies are missing:
conduit >=1.0 && <2.0,
data-default -any,
fast-logger >=2.1.4 && <2.2,
hjsmin ==0.1.*,
http-conduit ==2.1.*,
monad-control ==0.3.*,
monad-logger ==0.3.*,
persistent ==1.3.*,
persistent-sqlite ==1.3.*,
persistent-template ==1.3.*,
shakespeare ==2.0.*,
wai-extra ==2.1.*,
wai-logger ==2.1.*,
warp ==2.1.*,
yaml ==0.8.*,
yesod >=1.2.5 && <1.3,
yesod-auth ==1.3.*,
yesod-core >=1.2.12 && <1.3,
yesod-form ==1.3.*,
yesod-static ==1.2.*

Wha? I thought I just installed yesod, so why is it asking me to do it again? I can understand that it’s a sandbox so I suppose there is no look-through to the global package db. Makes some sense.

Anyway, trying to cabal install these manually in the sandbox ran me into a wall with network-2.5.0.0, which refused to compile in the sandbox but compiled fine outside it (wtf?). Okay, deleting the sandboxed cabal file and installing network-2.5.0.0 in the global package db seemed to work. At this point I was about 5 hours into getting this stuff to work after multiple reinstalls of Haskell Platform, blowing away ~/.ghc, upgrading cabal versions, etc. Getting tired of waiting for my machine to compile several hundred dependencies… this is why I stopped using Gentoo Linux - just give me stuff that works, please.

Okay, so now I remembered yesod-platform. Will try it first with a sandbox, then without. No dice with sandboxed version after about 30 minutes (tons of install failures having to do with network-2.5.0.0 again - clearly a real issue). Dropped sandbox and now running canonical command:

cabal install yesod-platform yesod-bin --max-backjumps=-1 --reorder-goals

Well, it finished the install without errors this time. Running yesod init gives me the message

Start your project:

   cd yesod-test && cabal sandbox init && cabal install --enable-tests .
   yesod-platform yesod-bin --max-backjumps=-1 --reorder-goals && yesod
   devel

but I’ve learned that this command leads back to perdition… so skipping ahead to the yesod devel part:

cabal: At least the following dependencies are missing:
persistent-postgresql ==1.3.*, wai-extra ==2.1.*, warp ==2.1.*

I chose to use postgresql, so I’m not that surprised by that one, but missing warp too? Seems odd since yesod usually runs on Warp, but whatever. Trying to install these manually yields… okay, persistent-postgresql was not a problem, but yesod wants older versions of wai-extra and warp. Looking up on hackage for anything in warp’s 2.1.* family led me to:

cabal install warp-2.1.5.2

Now I’m left with wai-extra. Hackage tells me that the latest is 3.0.0; not so lucky with installing 2.1.*:

$ cabal install wai-extra-2.1.1.2
Resolving dependencies...
In order, the following would be installed:
wai-logger-2.1.1 (reinstall) changes: wai-3.0.0 -> 2.1.0.3
zlib-conduit-1.1.0 (new package)
wai-extra-2.1.1.2 (latest: 3.0.0) (new version)
cabal: The following packages are likely to be broken by the reinstalls:
yesod-platform-1.2.12
yesod-core-1.2.16
yesod-test-1.2.3
...
Use --force-reinstalls if you want to install anyway.

So it’s telling me that if I want wai-extra I have to break Yesod, or I could force-reinstalls and risk breaking everything. Hmm… well, nothing to lose at this point.

cabal install wai-extra-2.1.1.2 --force-reinstalls

and… success? Now I have to check that I didn’t break anything, and I did (yesod devel is complaining about broken dependencies now). Then I attempt to --reinstall and --force-reinstalls on some packages as a last-ditch fix, but that seems to be going nowhere.

Well, that was one full workday attempting to install Yesod. I think that’s enough time invested for the next year or so. Perhaps by then the install issues will be smoothed out. It’s a shame because I thought the platform was otherwise really attractive. I hope that by spelling things out a bit here it can show how difficult/frustrating the process can be.