Solver takes over 10 minutes, resulting in a failed Travis build

[snoyberg]

You can see the Travis build here: https://travis-ci.org/yesodweb/yesod/jobs/199252979. Steps to reproduce:

1. Clone the repo https://github.com/yesodweb/yesod at commit 9ee3c3707441963835be04d38b14831c6d9e4b29.

2. With GHC 8.0.1 and cabal-install 1.24.0.0, run:
   cabal install --dry-run --only-dependencies --enable-tests --enable-benchmarks --force-reinstalls --ghc-options=-O0 --reorder-goals --max-backjumps=-1 yesod-bin/ yesod-websockets/ yesod-test/ yesod-core/ yesod-sitemap/ yesod-newsfeed/ yesod-persistent/ yesod/ yesod-form/ yesod-eventsource/ yesod-auth-oauth/ yesod-static/ yesod-auth/

3. I did this with an index last updated at 16:42 on 2017-02-07

Expected: the build plan can be calculated.

Actual: build plan took greater than 10 minutes, causing the Travis build to fail.

[phadej]

could you try cabal-head? it has much better solver.

[snoyberg]

Sure, I've just pushed a commit for that. Build should occur at:

https://travis-ci.org/yesodweb/yesod/jobs/199293637

EDIT Thanks for the super fast response :)

[23Skidoo]

Seems to be fixed in HEAD, that command takes 0.46 s on my machine. So closing.

[23Skidoo]

@snoyberg Do you need a fix for this issue backported to the 1.24 branch, or can you wait for the 2.0 release (which should be out at the same time as GHC 8.2)?

[snoyberg]

If it works with cabal-head, I can update the Travis job to just use that for 8.0.1, which should be fine overall. No need for this specific issue to cut a new release, but thank you. Worst case scenario, if HEAD turns out to be unstable, I'll just add this to an expected-failures case and leave the 8.0.1 testing to Stack.