Re: cabal install: mmorph dependency hell?

[John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org>]

Odd, it's trying to downgrade the version of transformers
that mmorph depends on.  I'm not sure why.  It could be that
one of the other packages it needs to install is incompatible
with the latest transformers (though I don't think that's the
case).  Or maybe one of the other pandoc dependencies that you
compiled earlier is linked against transformers-0.2.2.0.

Have you tried doing a 'cabal clean' before 'cabal install --reinstall'?

+++ Ben Bolker [Jan 04 14 15:30 ]:
>    I  have pandoc 1.11.1 installed via cabal on Ubuntu 12.04, trying to
>    update (I really want the "pause" functionality for slide shows).
>    I'm having trouble with the 'mmorph' dependency, which is reported to
>    fail when I 'cabal install pandoc' (after 'cabal update').   If I
>    'cabal install mmorph' it tells me it's already installed. If I 'cabal
>    install mmorph --reinstall' it appears to install correctly (see
>    below), but 'cabal install pandoc' still fails.
>    I only use cabal/haskell for pandoc, so I'm pretty clueless -- any help
>    would be greatly appreciated.
>    Two possible clues:
>    1. in the output below I see both
>         (mmorph reinstall): mmorph-1.0.1 (reinstall) changes:
>    transformers-0.3.0.0 -> 0.2.2.0
>    and
>       (failed mmorph install):
>        Could not find module `Control.Applicative.Backwards'
>        [...]
>        It is a member of the hidden package `transformers-0.3.0.0'.
>    Is there a dependency mismatch here somewhere?
>    2. I see from https://github.com/Gabriel439/Haskell-MMorph-Library that
>    mmorph 1.0.1 was only released 5 days ago, so maybe I'm among the first
>    to stumble on a new problem?
>      sincerely
>        Ben Bolker
>    $ cabal install pandoc
>    Resolving dependencies...
>    In order, the following will be installed:
>    mmorph-1.0.1 (reinstall) changes: transformers-0.3.0.0 -> 0.2.2.0
>    resourcet-0.4.10 (new package)
>    conduit-1.0.9.3 (new package)
>    blaze-builder-conduit-1.0.0 (new package)
>    yaml-0.8.5.2 (new package)
>    zlib-conduit-1.0.0 (new package)
>    http-conduit-1.9.6 (new package)
>    pandoc-1.12.2.1 (new package)
>    Warning: Note that reinstalls are always dangerous. Continuing
>    anyway...
>    Configuring mmorph-1.0.1...
>    Building mmorph-1.0.1...
>    Preprocessing library mmorph-1.0.1...
>    src/Control/Monad/Morph.hs:76:8:
>        Could not find module `Control.Applicative.Backwards'
>        It is a member of the hidden package `applicative-extras-0.1.8'.
>        Perhaps you need to add `applicative-extras' to the build-depends
>    in your .cabal file.
>        It is a member of the hidden package `transformers-0.3.0.0'.
>        Perhaps you need to add `transformers' to the build-depends in your
>    .cabal file.
>        Use -v to see a list of the files searched for.
>    cabal: Error: some packages failed to install:
>    blaze-builder-conduit-1.0.0 depends on mmorph-1.0.1 which failed to
>    install.
>    conduit-1.0.9.3 depends on mmorph-1.0.1 which failed to install.
>    http-conduit-1.9.6 depends on mmorph-1.0.1 which failed to install.
>    mmorph-1.0.1 failed during the building phase. The exception was:
>    ExitFailure 1
>    pandoc-1.12.2.1 depends on mmorph-1.0.1 which failed to install.
>    resourcet-0.4.10 depends on mmorph-1.0.1 which failed to install.
>    yaml-0.8.5.2 depends on mmorph-1.0.1 which failed to install.
>    zlib-conduit-1.0.0 depends on mmorph-1.0.1 which failed to install.
>     cabal install mmorph --reinstall
>    Resolving dependencies...
>    In order, the following will be installed:
>    mmorph-1.0.1 (reinstall)
>    Warning: Note that reinstalls are always dangerous. Continuing
>    anyway...
>    Configuring mmorph-1.0.1...
>    Building mmorph-1.0.1...
>    Preprocessing library mmorph-1.0.1...
>    [1 of 2] Compiling Control.Monad.Morph ( src/Control/Monad/Morph.hs,
>    dist/build/Control/Monad/Morph.o )
>    [2 of 2] Compiling Control.Monad.Trans.Compose (
>    src/Control/Monad/Trans/Compose.hs,
>    dist/build/Control/Monad/Trans/Compose.o )
>    Registering mmorph-1.0.1...
>    Installing library in /home/bolker/.cabal/lib/mmorph-1.0.1/ghc-7.4.1
>    Registering mmorph-1.0.1...
> 
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