disabledFlags

Stackage/LoadDatabase.hs

@@ -128,7 +128,9 @@ loadPackageDB settings core deps = do
           where
             checkCond' (Var (OS os)) = os == buildOS
             checkCond' (Var (Arch arch)) = arch == buildArch
-            checkCond' (Var (Flag flag)) = flag `elem` flags'
+            checkCond' (Var (Flag flag@(FlagName flag'))) =
+                flag' `Set.notMember` disabledFlags settings &&
+                flag `elem` flags'
             checkCond' (Var (Impl compiler range)) =
                 compiler == GHC && withinRange targetCompilerVersion range
             checkCond' (Lit b) = b

Stackage/Select.hs

@@ -23,6 +23,7 @@ defaultSelectSettings = SelectSettings
     , requireHaskellPlatform = True
     , excludedPackages = empty
     , flags = Set.fromList $ words "blaze_html_0_5"
+    , disabledFlags = Set.fromList $ words "bytestring-in-base"
     , allowedPackage = const $ Right ()
     , useGlobalDatabase = False
     }

Stackage/Types.hs

@@ -93,6 +93,8 @@ data SelectSettings = SelectSettings
     { haskellPlatformCabal   :: FilePath
     , flags                  :: Set String
     -- ^ Compile flags which should be turned on.
+    , disabledFlags          :: Set String
+    -- ^ Compile flags which should always be disabled.
     , extraCore              :: Set PackageName
     , requireHaskellPlatform :: Bool
     , allowedPackage         :: GenericPackageDescription -> Either String ()