Provide --exclude option (#7)

Stackage/Build.hs

@@ -19,6 +19,7 @@ import           System.Process       (runProcess, waitForProcess, rawSystem, re
 import           System.Directory     (createDirectoryIfMissing, canonicalizePath, doesDirectoryExist)
 import           Distribution.Version    (thisVersion, withinRange)
 import Control.Exception (assert)
+import Data.Set (empty)
 
 defaultBuildSettings :: BuildSettings
 defaultBuildSettings = BuildSettings
@@ -31,6 +32,7 @@ defaultBuildSettings = BuildSettings
     , haskellPlatformCabal = "haskell-platform/haskell-platform.cabal"
     , requireHaskellPlatform = True
     , cleanBeforeBuild = True
+    , excludedPackages = empty
     }
 
 build :: BuildSettings -> IO ()

Stackage/InstallInfo.hs

@@ -13,12 +13,19 @@ import           Stackage.Types
 import           Stackage.Util
 import Data.Version (showVersion)
 
+dropExcluded :: BuildSettings
+             -> Map PackageName (VersionRange, Maintainer)
+             -> Map PackageName (VersionRange, Maintainer)
+dropExcluded bs m0 =
+    Set.foldl' (flip Map.delete) m0 (excludedPackages bs)
+
 getInstallInfo :: BuildSettings -> IO InstallInfo
 getInstallInfo settings = do
     hp <- loadHaskellPlatform settings
-    let allPackages
+    let allPackages'
             | requireHaskellPlatform settings = Map.union (stablePackages settings) $ identsToRanges (hplibs hp)
             | otherwise = stablePackages settings
+        allPackages = dropExcluded settings allPackages'
     let totalCore = extraCore settings `Set.union` Set.map (\(PackageIdentifier p _) -> p) (hpcore hp)
     pdb <- loadPackageDB totalCore allPackages
     final <- narrowPackageDB pdb $ Set.fromList $ Map.toList $ Map.map snd $ allPackages

Stackage/Types.hs

@@ -64,4 +64,8 @@ data BuildSettings = BuildSettings
     , haskellPlatformCabal :: FilePath
     , requireHaskellPlatform :: Bool
     , cleanBeforeBuild :: Bool
+    , excludedPackages :: Set PackageName
+    -- ^ Packages which should be dropped from the list of stable packages,
+    -- even if present via the Haskell Platform or @stablePackages@. If these
+    -- packages are dependencies of others, they will still be included.
     }

app/stackage.hs

@@ -1,14 +1,34 @@
-import           Stackage.Types     (BuildSettings(..))
+{-# LANGUAGE RecordWildCards #-}
+import           Stackage.Types
 import           Stackage.Build     (build, defaultBuildSettings)
 import           Stackage.Init      (stackageInit)
 import           System.Environment (getArgs, getProgName)
+import           Data.Set           (fromList)
+
+data BuildArgs = BuildArgs
+    { noClean :: Bool
+    , excluded :: [String]
+    }
+
+parseBuildArgs :: [String] -> IO BuildArgs
+parseBuildArgs =
+    loop $ BuildArgs False []
+  where
+    loop x [] = return x
+    loop x ("--no-clean":rest) = loop x { noClean = True } rest
+    loop x ("--exclude":y:rest) = loop x { excluded = y : excluded x } rest
+    loop _ (y:_) = error $ "Did not understand argument: " ++ y
 
 main :: IO ()
 main = do
     args <- getArgs
     case args of
-        ["build"] -> build defaultBuildSettings
+        "build":rest -> do
-        ["build", "--no-clean"] -> build (defaultBuildSettings { cleanBeforeBuild = False })
+            BuildArgs {..} <- parseBuildArgs rest
+            build defaultBuildSettings
+                { cleanBeforeBuild = not noClean
+                , excludedPackages = fromList $ map PackageName excluded
+                }
         ["init"] -> stackageInit
         ["update"] -> stackageInit >> error "FIXME update"
         _ -> do
@@ -17,4 +37,5 @@ main = do
             putStrLn "Available commands:"
             putStrLn "    update              Download updated Stackage databases. Automatically calls init."
             putStrLn "    init                Initialize your cabal file to use Stackage"
-            putStrLn "    build [--no-clean]  Build the package databases (maintainers only)"
+            putStrLn "    build [--no-clean] [--exclude package...]"
+            putStrLn "                        Build the package databases (maintainers only)"

stackage.cabal

@@ -39,6 +39,7 @@ executable stackage
   main-is:             stackage.hs
   build-depends:       base
                      , stackage
+                     , containers
 
 source-repository head
   type:     git