fix for Trac #164: better error reporting for undefined flags

Distribution/Configuration.hs

@@ -47,7 +47,7 @@ module Distribution.Configuration (
     Flag(..),
     ConfVar(..),
     Condition(..), parseCondition, simplifyCondition,
-    CondTree(..), ppCondTree, mapTreeData,
+    CondTree(..), ppCondTree, mapTreeData, freeVars,
     --satisfyFlags, 
     resolveWithFlags, ignoreConditions,
     DepTestRslt(..)
@@ -382,6 +382,18 @@ ignoreConditions (CondNode a c ifs) = (a, c) `mappend` mconcat (concatMap f ifs)
   where f (_, t, me) = ignoreConditions t 
                        : maybeToList (fmap ignoreConditions me)
 
+freeVars :: CondTree ConfVar c a  -> [String]
+freeVars t = [ s | Flag (ConfFlag s) <- freeVars' t ]
+  where
+    freeVars' (CondNode _ _ ifs) = concatMap compfv ifs
+    compfv (c, ct, mct) = condfv c ++ freeVars' ct ++ maybe [] freeVars' mct
+    condfv c = case c of
+      Var v      -> [v]
+      Lit _      -> []
+      CNot c'    -> condfv c'
+      COr c1 c2  -> condfv c1 ++ condfv c2
+      CAnd c1 c2 -> condfv c1 ++ condfv c2
+
 ------------------------------------------------------------------------------
 -- Testing
 

Distribution/PackageDescription.hs

@@ -109,7 +109,7 @@ module Distribution.PackageDescription (
 import Control.Monad(liftM, foldM, when)
 import Data.Char
 import Data.Maybe(isNothing, isJust, catMaybes, listToMaybe, maybeToList)
-import Data.List (nub, maximumBy, unfoldr, partition)
+import Data.List (nub, maximumBy, unfoldr, partition, (\\), intersperse)
 import Text.PrettyPrint.HughesPJ as Pretty
 import System.Directory(doesFileExist)
 
@@ -947,6 +947,7 @@ parsePackageDescription file = do
       warnIfRest
       when (not (oldSyntax fields0)) $
         maybeWarnCabalVersion pkg
+      checkForUndefinedFlags flags mlib exes
       return (GenericPackageDescription pkg flags mlib exes)
 
   where
@@ -1117,6 +1118,23 @@ parsePackageDescription file = do
     parseExeFields :: [Field] -> StT s ParseResult Executable
     parseExeFields = lift . parseFields executableFieldDescrs nullExecutable
 
+    checkForUndefinedFlags ::
+        [Flag] ->
+        Maybe (CondTree ConfVar [Dependency] Library) ->
+        [(String, CondTree ConfVar [Dependency] Executable)] ->
+        PM ()
+    checkForUndefinedFlags flags mlib exes = do
+        let definedFlags = map flagName flags
+        maybe (return ()) (checkCondTreeFlags definedFlags) mlib
+        mapM_ (checkCondTreeFlags definedFlags . snd) exes
+
+    checkCondTreeFlags :: [String] -> CondTree ConfVar c a -> PM ()
+    checkCondTreeFlags definedFlags ct = do
+        let fv = nub $ freeVars ct
+        when (not . all (`elem` definedFlags) $ fv) $
+            error $ "Undefined flag(s) encountered: " ++
+                    (concat . intersperse " " $ (fv \\ definedFlags))
+
 
 parseFields :: [FieldDescr a] -> a  -> [Field] -> ParseResult a
 parseFields descrs ini fields =