Refactor the way packages databases are handled

- cradle now stores a list of active package databases instead of only
  the user store (if present).

- rename `cradlePackageDb` -> `cradlePkgDbStack` as that`s what the ghc
  documentaion calls this kind of thing

- `getPackageDbPackages` now returns names of all visible packages in
  the given directory. Also the implementation now uses `ghc-pkg`
  instead of manually looking at the package database

test/CradleSpec.hs

@@ -4,7 +4,7 @@ import Control.Applicative
 import Data.List (isSuffixOf)
 import Language.Haskell.GhcMod.Cradle
 import Language.Haskell.GhcMod.Types
-import System.Directory (canonicalizePath)
+import System.Directory (canonicalizePath,getCurrentDirectory)
 import System.FilePath ((</>), pathSeparator)
 import Test.Hspec
 
@@ -21,17 +21,18 @@ spec = do
                     cradleCurrentDir = curDir
                   , cradleRootDir    = curDir
                   , cradleCabalFile  = Nothing
-                  , cradlePackageDb  = Nothing
+                  , cradlePkgDbStack = [GlobalDb]
                   , cradlePackages   = []
                   }
         it "finds a cabal file and a sandbox" $ do
+            cwd <- getCurrentDirectory
             withDirectory "test/data/subdir1/subdir2" $ \dir -> do
                 res <- relativeCradle dir <$> findCradle
                 res `shouldBe` Cradle {
                     cradleCurrentDir = "test" </> "data" </> "subdir1" </> "subdir2"
                   , cradleRootDir    = "test" </> "data"
                   , cradleCabalFile  = Just ("test" </> "data" </> "cabalapi.cabal")
-                  , cradlePackageDb  = Just ("test" </> "data" </> ".cabal-sandbox" </> "/home/me/work/ghc-mod/test/data/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d")
+                  , cradlePkgDbStack = [GlobalDb, PackageDb (cwd </> "test/data/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d")]
                   , cradlePackages   = []
                   }
         it "works even if a sandbox config file is broken" $ do
@@ -41,23 +42,10 @@ spec = do
                     cradleCurrentDir = "test" </> "data" </> "broken-sandbox"
                   , cradleRootDir    = "test" </> "data" </> "broken-sandbox"
                   , cradleCabalFile  = Just ("test" </> "data" </> "broken-sandbox" </> "dummy.cabal")
-                  , cradlePackageDb  = Nothing
+                  , cradlePkgDbStack = [GlobalDb, UserDb]
                   , cradlePackages   = []
                   }
 
-    describe "getPackageDbDir" $ do
-        it "parses a config file and extracts package db" $ do
-            pkgDb <- getPackageDbDir "test/data/cabal.sandbox.config"
-            pkgDb `shouldBe` "/home/me/work/ghc-mod/test/data/.cabal-sandbox/i386-osx-ghc-7.6.3-packages.conf.d"
-
-        it "throws an error if a config file is broken" $ do
-            getPackageDbDir "test/data/bad.config" `shouldThrow` anyException
-
-    describe "getPackageDbPackages" $ do
-        it "find a config file and extracts packages with their ids" $ do
-            pkgs <- getPackageDbPackages "test/data/check-packageid"
-            pkgs `shouldBe` [("template-haskell", Just "template-haskell-2.8.0.0-32d4f24abdbb6bf41272b183b2e23e9c")]
-
 relativeCradle :: FilePath -> Cradle -> Cradle
 relativeCradle dir cradle = cradle {
     cradleCurrentDir    = toRelativeDir dir  $  cradleCurrentDir cradle