Pinpointing in which modules the packages couldn't be found

cabal-install/src/Distribution/Client/Init/Interactive/Command.hs

@@ -455,4 +455,4 @@ dependenciesPrompt
     -> InitFlags
     -> m [Dependency]
 dependenciesPrompt pkgIx flags = getDependencies flags $
-    retrieveDependencies flags [fromString "Prelude"] pkgIx
+    retrieveDependencies flags [(fromString "Prelude", fromString "Prelude")] pkgIx

cabal-install/src/Distribution/Client/Init/NonInteractive/Command.hs

@@ -442,12 +442,11 @@ dependenciesHeuristics flags fp pkgIx = getDependencies flags $ do
         Flag x -> x
         NoFlag -> map moduleName sources
 
-  retrieveDependencies flags
-    ( nub                    -- skips duplicates
-    ( fromString "Prelude"    -- gets base as dependency
-    : (filter (`notElem` mods) -- skips modules from this own package
-    . concatMap imports $ sources)))
-    pkgIx
+      groupedDeps  = concatMap (\s -> map (\i -> (moduleName s, i)) (imports s)) sources
+      filteredDeps = filter ((`notElem` mods) . snd) groupedDeps
+      preludeNub   = nubBy (\a b -> snd a == snd b) $ (fromString "Prelude", fromString "Prelude") : filteredDeps
+
+  retrieveDependencies flags preludeNub pkgIx
 
 -- | Retrieve the list of extensions
 otherExtsHeuristics :: Interactive m => InitFlags -> FilePath -> m [Extension]

cabal-install/src/Distribution/Client/Init/Utils.hs

@@ -213,15 +213,15 @@ isSourceFile :: Maybe [FilePath] -> SourceFileEntry -> Bool
 isSourceFile Nothing        sf = isSourceFile (Just ["."]) sf
 isSourceFile (Just srcDirs) sf = any (equalFilePath (relativeSourcePath sf)) srcDirs
 
-retrieveDependencies :: Interactive m => InitFlags -> [ModuleName] -> InstalledPackageIndex -> m [P.Dependency]
+retrieveDependencies :: Interactive m => InitFlags -> [(ModuleName, ModuleName)] -> InstalledPackageIndex -> m [P.Dependency]
 retrieveDependencies flags mods' pkgIx = do
   let mods = mods'
 
       modMap :: M.Map ModuleName [InstalledPackageInfo]
       modMap  = M.map (filter exposed) $ moduleNameIndex pkgIx
 
-      modDeps :: [(ModuleName, Maybe [InstalledPackageInfo])]
-      modDeps = map (\mn -> (mn, M.lookup mn modMap)) mods
+      modDeps :: [(ModuleName, ModuleName, Maybe [InstalledPackageInfo])]
+      modDeps = map (\(mn, ds) -> (mn, ds, M.lookup ds modMap)) mods
       -- modDeps = map (id &&& flip M.lookup modMap) mods
 
   message (fromFlagOrDefault silent $ initVerbosity flags) "\nGuessing dependencies..."
@@ -233,9 +233,9 @@ retrieveDependencies flags mods' pkgIx = do
 chooseDep
   :: Interactive m
   => InitFlags
-  -> (ModuleName, Maybe [InstalledPackageInfo])
+  -> (ModuleName, ModuleName, Maybe [InstalledPackageInfo])
   -> m (Maybe P.Dependency)
-chooseDep flags (m, mipi) = case mipi of
+chooseDep flags (importer, m, mipi) = case mipi of
   -- We found some packages: group them by name.
   Just ps@(_:_) ->
     case NE.groupBy (\x y -> P.pkgName x == P.pkgName y) $ map P.packageId ps of
@@ -268,7 +268,7 @@ chooseDep flags (m, mipi) = case mipi of
         return Nothing
 
   _ -> do
-    message v ("\nWarning: no package found providing " ++ prettyShow m ++ ".")
+    message v ("\nWarning: no package found providing " ++ prettyShow m ++ " in " ++ prettyShow importer ++ ".")
     return Nothing
 
   where