hpodder compile problem (HaXml)

[Martin Møller Skarbiniks Pedersen]

Hi,

I am writing because I want to install a program called hpodder
which is written in Haskell.
  I am using Fedora 19 beta with these Haskell packages installed:
$ rpm -qa | grep haskell
ghc-haskell98-2.0.0.1-11.fc19.x86_64
ghc-haskell-platform-devel-2012.4.0.0-22.fc19.x86_64
ghc-template-haskell-2.7.0.0-11.fc19.x86_64
ghc-haskell2010-devel-1.1.0.1-11.fc19.x86_64
ghc-haskell-src-devel-1.0.1.5-22.fc19.x86_64
ghc-haskell98-devel-2.0.0.1-11.fc19.x86_64
ghc-template-haskell-devel-2.7.0.0-11.fc19.x86_64
haskell-platform-2012.4.0.0-22.fc19.x86_64
ghc-haskell2010-1.1.0.1-11.fc19.x86_64
ghc-haskell-src-1.0.1.5-22.fc19.x86_64

My attempts to compile this program fails and my Haskell skills are
quite limited.

To reproduce:

1.  git clone https://github.com/jgoerzen/hpodder.git
  2.  cd hpodder
  3.  cabal install
Resolving dependencies...
Configuring HaXml-1.20.2...
Building HaXml-1.20.2...
Preprocessing library HaXml-1.20.2...

src/Text/XML/HaXml.hs:1:1:
    Ambiguous module name `Prelude':
      it was found in multiple packages: base haskell98-2.0.0.1
cabal: Error: some packages failed to install:
HaXml-1.20.2 failed during the building phase. The exception was:
ExitFailure 1

4. ./setup configure
Configuring hpodder-1.1.6...
setup: At least the following dependencies are missing:
ConfigFile -any,
HDBC >=1.1.0,
HDBC-sqlite3 >=1.1.0,
HaXml ==1.20.*,
MissingH >=1.0.0,
hslogger -any
make: *** [all] Error 1

Regards
Martin
Bevar misundelsesafgifterne og cafepengene!
Hurra for ældrebyrden!

[Jens-Ulrik Petersen]

Hi Martin,
> Resolving dependencies...
> Configuring HaXml-1.20.2...
> Building HaXml-1.20.2...
> Preprocessing library HaXml-1.20.2...
>
> src/Text/XML/HaXml.hs:1:1:
>     Ambiguous module name `Prelude':
>       it was found in multiple packages: base haskell98-2.0.0.1
> cabal: Error: some packages failed to install:
> HaXml-1.20.2 failed during the building phase. The exception was:
> ExitFailure 1

You will probably have more luck building it with ghc-7.0...

I see the same here on F19.

I think best to contact the hpodder author for help on fixing this
(ie with getting it to build with ghc-7.4).
Newer (latest) HaXml seems to build ok with ghc-7.4 (f19),
but current hpodder does not seem happy with it:

Commands/Ls.hs:86:11:
    Could not deduce (PrintfType (m a0))
      arising from the ambiguity check for `printep'
    from the context (Monad m, PrintfType (m ()), PrintfType (m a))
      bound by the inferred type for `printep':
                 (Monad m, PrintfType (m ()), PrintfType (m a)) => Episode -> m ()
      at Commands/Ls.hs:(86,11)-(90,69)
    Possible fix: add an instance declaration for (PrintfType (m a0))
    When checking that `printep'
      has the inferred type `forall (m :: * -> *) a.
                             (Monad m, PrintfType (m ()), PrintfType (m a)) =>
                             Episode -> m ()'
    Probable cause: the inferred type is ambiguous
    In an equation for `lsepisodes_worker':
        lsepisodes_worker gi (opts, casts)
          = do { pc <- getSelectedPodcasts (gdbh gi) casts;
                 printf
                   "%-5s %-5s %-4s %-60.60s" "CstId" "EpId" "Stts" "Episode Title";
                 when (islong) (printf "            Episode URL");
                 .... }
          where
              printep ep
                = do { printf
                         "%-5d %-5d %-4s %-60.60s"
                         (castid (podcast ep))
                         (epid ep)
                         (take 4 . show $ epstatus ep)
                         (eptitle ep);
                       .... }
              islong = lookup "l" opts == Just ""

(above error is not related to the HaXml version).

Jens

ps For posterity I attached a patch to make HaXml-1.20 library build with ghc-7.4
but that does not fix the above problem with compiling hpodder
(ie hpodder /might/ perhaps build okay with latest HaXml).

[Jens-Ulrik Petersen]

> I think best to contact the hpodder author for help on fixing this
> (ie with getting it to build with ghc-7.4).
> Newer (latest) HaXml seems to build ok with ghc-7.4 (f19),
> but current hpodder does not seem happy with it:
>
> Commands/Ls.hs:86:11:
>     Could not deduce (PrintfType (m a0))
>       arising from the ambiguity check for `printep'
>     from the context (Monad m, PrintfType (m ()), PrintfType (m a))

Ah I think someone has probably already done the work:
see https://github.com/jgoerzen/hpodder/pull/10