Cabal issue when compiling snaplet-mongodb-minimalistic

Question

Can anyone help me solve this. I am trying to compile Example 1 from the snaplet-mongodb-minimalistic package, but I get the following error:

$ cabal install
Resolving dependencies...
cabal.exe: Could not resolve dependencies:
trying: snaplet-mongodb-minimalistic-example1-0.0.1 (user goal)
trying: mongoDB-1.3.0/installed-137... (dependency of
snaplet-mongodb-minimalistic-example1-0.0.1)
trying: transformers-base-0.4.1/installed-9d4... (dependency of
mongoDB-1.3.0/installed-137...)
next goal: snap-server (dependency of
snaplet-mongodb-minimalistic-example1-0.0.1)
rejecting: snap-server-0.9.0/installed-5b0..., 0.9.0, 0.8.1.1, 0.8.1, 0.8.0.1,
0.8.0 (conflict: snaplet-mongodb-minimalistic-example1 => snap-server==0.7.)
rejecting: snap-server-0.7.0.1 (conflict: transformers-base =>
transformers==0.3.0.0/installed-e82..., snap-server => transformers>=0.2 &&
rejecting: snap-server-0.7 (conflict: mongoDB =>
array==0.4.0.0/installed-3cf..., snap-server => array>=0.2 && rejecting: snap-server-0.6.0.1, 0.6.0, 0.5.5, 0.5.4, 0.5.3.1, 0.5.3, 0.5.2,
0.5.1.4, 0.5.1.3, 0.5.1.2, 0.5.1.1, 0.5.1, 0.5.0, 0.4.3, 0.4.2, 0.4.1,
0.4.0.2, 0.4.0.1, 0.4.0, 0.3.1.1, 0.3.1, 0.3.0, 0.2.16.2, 0.2.16.1, 0.2.16,
0.2.15.1, 0.2.15, 0.2.14.1, 0.2.14, 0.2.13.3, 0.2.13.2, 0.2.13.1, 0.2.13,
0.2.12, 0.2.11, 0.2.10.2, 0.2.10.1, 0.2.10, 0.2.9, 0.2.8.1, 0.2.8, 0.2.7.2,
0.2.7.1, 0.2.7, 0.2.6, 0.2.5, 0.2.4, 0.2.2, 0.2.1, 0.1.4, 0.1.3, 0.1.2, 0.1.1
(conflict: snaplet-mongodb-minimalistic-example1 => snap-server==0.7.)

I've filed an issue with the author, but he seems to be busy. If I can fix this, I'll submit a fix.

Answer 1

snaplet-mongodb-minimalistic depends on snap-core == 0.9.* while example-1 depends on snap-core == 0.7.* (and snap-server). The result is the wonderful cascade of dependency failures you're seeing. You have to go over dependencies of example-1 and make sure there are no version conflicts anywhere.