Move some 'PyValue' instances to a separate file

Move some 'PyValue' instances to a separate file so they can be
available to other modules which need these instances but do not want
to depend on the constants module, which led to compilation
constraints.
Signed-off-by: Jose A. Lopes <jabolopes@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Makefile.am

@@ -644,6 +644,7 @@ HS_LIB_SRCS = \
 	src/Ganeti/OpParams.hs \
 	src/Ganeti/Path.hs \
 	src/Ganeti/Parsers.hs \
+	src/Ganeti/PyValueInstances.hs \
 	src/Ganeti/Query/Cluster.hs \
 	src/Ganeti/Query/Common.hs \
 	src/Ganeti/Query/Export.hs \

src/Ganeti/OpCodes.hs

@@ -52,36 +52,15 @@ import Ganeti.THH
 
 import qualified Ganeti.Hs2Py.OpDoc as OpDoc
 import Ganeti.OpParams
+import Ganeti.PyValueInstances ()
 import Ganeti.Types
 import Ganeti.Query.Language (queryTypeOpToRaw)
 
 import Data.List (intercalate)
 import Data.Map (Map)
-import qualified Data.Map as Map
-import Data.Set (Set)
-import qualified Data.Set as Set
 
 import qualified Ganeti.Constants as C
 
-instance PyValue Bool
-instance PyValue Int
-instance PyValue Double
-instance PyValue Char
-
-instance (PyValue a, PyValue b) => PyValue (a, b) where
-  showValue (x, y) = show (showValue x, showValue y)
-
-instance PyValue a => PyValue [a] where
-  showValue xs = show (map showValue xs)
-
-instance PyValue a => PyValue (Set a) where
-  showValue s = showValue (Set.toList s)
-
-instance (PyValue k, PyValue a) => PyValue (Map k a) where
-  showValue mp =
-    "{" ++ intercalate ", " (map showPair (Map.assocs mp)) ++ "}"
-    where showPair (k, x) = show k ++ ":" ++ show x
-
 instance PyValue DiskIndex where
   showValue = showValue . unDiskIndex
 

src/Ganeti/PyValueInstances.hs

+{-| PyValueInstances contains instances for the 'PyValue' typeclass.
+
+The typeclass 'PyValue' converts Haskell values to Python values.
+This module contains instances of this typeclass for several generic
+types.  These instances are used in the Haskell to Python generation
+of opcodes and constants, for example.
+
+-}
+
+{-
+
+Copyright (C) 2013 Google Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.
+
+-}
+{-# LANGUAGE FlexibleInstances, OverlappingInstances,
+             TypeSynonymInstances, IncoherentInstances #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+module Ganeti.PyValueInstances where
+
+import Data.List (intercalate)
+import Data.Map (Map)
+import qualified Data.Map as Map
+import Data.Set (Set)
+import qualified Data.Set as Set
+
+import Ganeti.THH
+
+instance PyValue Bool
+instance PyValue Int
+instance PyValue Double
+instance PyValue Char
+
+instance (PyValue a, PyValue b) => PyValue (a, b) where
+  showValue (x, y) = show (showValue x, showValue y)
+
+instance PyValue String where
+  showValue = show
+
+instance PyValue a => PyValue [a] where
+  showValue xs = show (map showValue xs)
+
+instance (PyValue k, PyValue a) => PyValue (Map k a) where
+  showValue mp =
+    "{" ++ intercalate ", " (map showPair (Map.assocs mp)) ++ "}"
+    where showPair (k, x) = show k ++ ":" ++ show x
+
+instance PyValue a => PyValue (Set a) where
+  showValue s = showValue (Set.toList s)