Can't install snap

[jamnut]

$ cabal install snap
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: snap-0.13.2.5 (user goal)
trying: snap-0.13.2.5:-old-base
trying: lens-4.1.2.1 (dependency of snap-0.13.2.5:-old-base)
trying: transformers-compat-0.3 (dependency of lens-4.1.2.1)
trying: transformers-compat-0.3:-transformers2
next goal: transformers (dependency of snap-0.13.2.5)
rejecting: transformers-0.3.0.0/installed-ff2... (conflict:
transformers-compat-0.3:transformers2 => transformers>=0.4 && <0.5)
rejecting: transformers-0.4.1.0 (conflict: snap => transformers>=0.2 && <0.4)
rejecting: transformers-0.3.0.0, 0.2.2.1, 0.2.2.0, 0.2.1.0, 0.2.0.0 (conflict:
transformers-compat-0.3:transformers2 => transformers>=0.4 && <0.5)
rejecting: transformers-0.1.4.0, 0.1.3.0, 0.1.1.0, 0.1.0.1, 0.1.0.0, 0.0.1.0,
0.0.0.0, 0.4.0.0 (conflict: snap => transformers>=0.2 && <0.4)
Backjump limit reached (change with --max-backjumps).

$ cabal --version
cabal-install version 1.20.0.1
using version 1.20.0.0 of the Cabal library 

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.6.3

[dbp]

I had a similar problem and was able to resolve it with --reorder-goals - maybe that will work? Seems to (maybe) be an upstream issue haskell/cabal#1855

[jamnut]

Works great. Thanks!

[bergmark]

Also, like the output says you can try e.g. --max-backjumps=4000 (or -1 for unlimited). The default is very low (100 or so) and has been increased on Cabal's master branch. Edit: Read the cabal issue, --max-backjumps should help, but may not here it looks like.

[dbp]

@bergmark Yeah in my case (and @snoyberg 's), it was having that issue even after an exhaustive search with --max-backjumps=-1 (hence it most likely being a bug, as that shouldn't be possible).

[kosmikus]

Yes, it definitely is a bug. That it can be worked around with --reorder-goals in this case is just a fortunate coincidence. Please see haskell/cabal#1855 and haskell/cabal#1878 for updates.

[victoredwardocallaghan]

I hit this too

[lsmag]

Hi guys, I just installed Cabal and I'm still having this issue, even with --reorder-goals and/or --max-backjumps=-1.

These are my GHC & Cabal versions:

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.4

$ cabal --version
cabal-install version 1.22.0.0
using version 1.22.0.0 of the Cabal library 

Anytime I run cabal clean; cabal install -fdevelopment, I get that "Backjump limit reached" error. Trying just --reorder-goals will still going to fail sooner or later, but when using --max-backjumps=-1 the process ends consuming 80% of my RAM and half my CPI until I decide to end it.

I'm already aware that this might be a cabal bug (I'm subscribed to haskell/cabal#1855), but is there any other quickfix I can use to continue my development?

[mightybyte]

Try using cabal 1.20. I've had issues with 1.22, so I have stayed on
1.20. No guarantees this will solve the problem, but it's worth a try. To
help any more I'll need a lot more information. It might be easier to sort
this out on the #snapframework IRC channel.

On Fri, Mar 6, 2015 at 10:42 PM, lsmag [email protected] wrote:

Hi guys, I just installed Cabal and I'm still having this issue, even with
--reorder-goals and/or --max-backjumps=-1.

These are my GHC & Cabal versions:

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.4

$ cabal --version
cabal-install version 1.22.0.0
using version 1.22.0.0 of the Cabal library

Anytime I run cabal clean; cabal install -fdevelopment, I get that "Backjump
limit reached" error. Trying just --reorder-goals will still going to
fail sooner or later, but when using --max-backjumps=-1 the process ends
consuming 80% of my RAM and half my CPI until I decide to end it.

I'm already aware that this might be a cabal bug (I'm subscribed to
haskell/cabal#1855 haskell/cabal#1855), but
is there any other quickfix I can use to continue my development?

—
Reply to this email directly or view it on GitHub
#195 (comment)
.

[cartazio]

for people who hit issues that mention transformers, my recommended directions are

1. add constraint: transformers installed to your ~/.cabal/config
2. rm -rf ~/.ghc
3. get back to work :)

[mightybyte]

Just to follow up, the solution @cartazio recommended seems to work. If you don't want to put that constraint in your global config you can add the flag --constraint='transformers installed' to your cabal install command. Also, regarding my above advice against 1.22, it looks like cabal-install-1.22.4.0 may have fixed some of the problems I was seeing with earlier 1.22 versions.

The "transformers installed" constraint seems to be working for everyone I've talked to, so I'm going to close this issue.

[kosmikus]

Should it be the case that there are still problems occurring with transformers in current cabal-install releases, I'd like to know about it.

[jenyckee]

~/sandbox/snap master*λ cabal --version
cabal-install version 1.24.0.0
compiled using version 1.24.0.0 of the Cabal library 
~/sandbox/snap master*λ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.0.1
~/sandbox/snap master*λ cabal install snap --constraint='transformers installed'
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: snap-0.14.0.7 (user goal)
trying: base-4.9.0.0/installed-4.9... (dependency of snap-0.14.0.7)
next goal: template-haskell (dependency of snap-0.14.0.7)
rejecting: template-haskell-2.11.0.0/installed-2.1...,
template-haskell-2.11.0.0 (conflict: snap => template-haskell>=2.2 && <2.11)
rejecting: template-haskell-2.10.0.0 (conflict:
base==4.9.0.0/installed-4.9..., template-haskell => base==4.8.*)
rejecting: template-haskell-2.9.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.7.*)
rejecting: template-haskell-2.8.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.6.*)
rejecting: template-haskell-2.7.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.5.*)
rejecting: template-haskell-2.6.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.4.*)
rejecting: template-haskell-2.5.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.3.*)
rejecting: template-haskell-2.4.0.1 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base==4.2.*)
rejecting: template-haskell-2.4.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base>=3 && <4.3)
rejecting: template-haskell-2.3.0.1, template-haskell-2.3.0.0,
template-haskell-2.2.0.0 (conflict: base==4.9.0.0/installed-4.9...,
template-haskell => base<4.3)
Dependency tree exhaustively searched.
~/sandbox/snap master*λ 

Still having this

[mightybyte]

Snap 0.14 doesn't support GHC 8. Try building against the most recent code in the github master branch.