Look up build tools packages based on executables (fixes #30)

Stackage/Build.hs

@@ -7,10 +7,12 @@ module Stackage.Build
 import           Control.Exception    (assert)
 import           Control.Monad        (unless, when)
 import qualified Data.Map             as Map
+import           Data.Maybe           (mapMaybe)
 import           Data.Set             (empty)
 import qualified Data.Set             as Set
 import           Distribution.Text    (simpleParse)
 import           Distribution.Version (withinRange)
+import           Prelude              hiding (pi)
 import           Stackage.CheckPlan
 import           Stackage.Config
 import           Stackage.InstallInfo
@@ -142,7 +144,7 @@ iiBuildTools InstallInfo { iiPackageDB = PackageDB m, iiPackages = packages } =
     -- tools themselves, and install them in the correct order.
     map unPackageName
   $ filter (flip Set.notMember coreTools)
-  $ filter (flip Map.member m)
+  $ mapMaybe (flip Map.lookup buildToolMap)
   $ Set.toList
   $ Set.unions
   $ map piBuildTools
@@ -156,3 +158,11 @@ iiBuildTools InstallInfo { iiPackageDB = PackageDB m, iiPackages = packages } =
     -- Build tools shipped with GHC which we should not attempt to build
     -- ourselves.
     coreTools = Set.fromList $ map PackageName $ words "hsc2hs"
+
+    -- The map from build tool name to the package it comes from.
+    buildToolMap = Map.unions $ map toBuildToolMap $ Map.toList m
+    toBuildToolMap :: (PackageName, PackageInfo) -> Map Executable PackageName
+    toBuildToolMap (pn, pi) = Map.unions
+                            $ map (flip Map.singleton pn)
+                            $ Set.toList
+                            $ piExecs pi

Stackage/LoadDatabase.hs

@@ -71,13 +71,14 @@ loadPackageDB settings core deps = do
                         _ ->
                             case Tar.entryContent e of
                                 Tar.NormalFile bs _ -> do
-                                    let (deps', hasTests, buildTools', mgpd) = parseDeps bs
+                                    let (deps', hasTests, buildTools', mgpd, execs) = parseDeps bs
                                     return $ mappend pdb $ PackageDB $ Map.singleton p PackageInfo
                                         { piVersion = v
                                         , piDeps = deps'
                                         , piHasTests = hasTests
                                         , piBuildTools = buildTools'
                                         , piGPD = mgpd
+                                        , piExecs = execs
                                         }
                                 _ -> return pdb
 
@@ -89,8 +90,11 @@ loadPackageDB settings core deps = do
                 , mconcat $ map (go gpd . snd) $ condTestSuites gpd
                 , mconcat $ map (go gpd . snd) $ condBenchmarks gpd
                 ], not $ null $ condTestSuites gpd
-                , Set.fromList $ map depName $ allBuildInfo gpd, Just gpd)
-            _ -> (mempty, defaultHasTestSuites, Set.empty, Nothing)
+                , Set.fromList $ map depName $ allBuildInfo gpd
+                , Just gpd
+                , Set.fromList $ map (Executable . fst) $ condExecutables gpd
+                )
+            _ -> (mempty, defaultHasTestSuites, Set.empty, Nothing, Set.empty)
       where
         allBuildInfo gpd = concat
             [ maybe mempty (goBI libBuildInfo) $ condLibrary gpd
@@ -100,7 +104,7 @@ loadPackageDB settings core deps = do
             ]
           where
             goBI f x = buildTools $ f $ condTreeData x
-        depName (Dependency p _) = p
+        depName (Dependency (PackageName p) _) = Executable p
         go gpd tree
             = Map.unionsWith unionVersionRanges
             $ Map.fromList (map (\(Dependency p vr) -> (p, vr)) $ condTreeConstraints tree)

Stackage/Types.hs

@@ -30,11 +30,15 @@ data PackageInfo = PackageInfo
     { piVersion    :: Version
     , piDeps       :: Map PackageName VersionRange
     , piHasTests   :: Bool
-    , piBuildTools :: Set PackageName
+    , piBuildTools :: Set Executable
     , piGPD        :: Maybe GenericPackageDescription
+    , piExecs      :: Set Executable
     }
     deriving (Show, Eq)
 
+newtype Executable = Executable String
+    deriving (Show, Eq, Ord)
+
 -- | Information on a package we're going to build.
 data BuildInfo = BuildInfo
     { biVersion    :: Version