Fix parsing of atypical ghc versions

app/ghcup/BrickMain.hs

@@ -10,6 +10,7 @@ module BrickMain where
 import           GHCup
 import           GHCup.Download
 import           GHCup.Errors
+import           GHCup.Types.Optics ( getDirs )
 import           GHCup.Types         hiding ( LeanAppState(..) )
 import           GHCup.Utils
 import           GHCup.Utils.Logger
@@ -40,6 +41,8 @@ import           Data.Vector                    ( Vector
 import           Data.Versions           hiding ( str )
 import           Haskus.Utils.Variant.Excepts
 import           Prelude                 hiding ( appendFile )
+import           System.Directory               ( canonicalizePath )
+import           System.FilePath
 import           System.Exit
 import           System.IO.Unsafe
 import           Text.PrettyPrint.HughesPJClass ( prettyShow )
@@ -48,6 +51,8 @@ import           URI.ByteString
 import qualified Data.Text                     as T
 import qualified Graphics.Vty                  as Vty
 import qualified Data.Vector                   as V
+import System.Environment (getExecutablePath)
+import qualified System.Posix.Process          as SPP
 
 
 hiddenTools :: [Tool]
@@ -432,27 +437,42 @@ install' _ (_, ListResult {..}) = do
               ]
 
   run (do
+      ce <- liftIO $ fmap (either (const Nothing) Just) $
+        try @_ @SomeException $ getExecutablePath >>= canonicalizePath
+      dirs <- lift getDirs
       case lTool of
         GHC   -> do
           let vi = getVersionInfo lVer GHC dls
-          liftE $ installGHCBin lVer Nothing False $> vi
+          liftE $ installGHCBin lVer Nothing False $> (vi, dirs, ce)
         Cabal -> do
           let vi = getVersionInfo lVer Cabal dls
-          liftE $ installCabalBin lVer Nothing False $> vi
+          liftE $ installCabalBin lVer Nothing False $> (vi, dirs, ce)
         GHCup -> do
           let vi = snd <$> getLatest dls GHCup
-          liftE $ upgradeGHCup Nothing False $> vi
+          liftE $ upgradeGHCup Nothing False $> (vi, dirs, ce)
         HLS   -> do
           let vi = getVersionInfo lVer HLS dls
-          liftE $ installHLSBin lVer Nothing False $> vi
+          liftE $ installHLSBin lVer Nothing False $> (vi, dirs, ce)
         Stack -> do
           let vi = getVersionInfo lVer Stack dls
-          liftE $ installStackBin lVer Nothing False $> vi
+          liftE $ installStackBin lVer Nothing False $> (vi, dirs, ce)
     )
     >>= \case
-          VRight vi                         -> do
-            forM_ (_viPostInstall =<< vi) $ \msg ->
-              logInfo msg
+          VRight (vi, Dirs{..}, Just ce) -> do
+            forM_ (_viPostInstall =<< vi) $ \msg -> logInfo msg
+            case lTool of
+              GHCup -> do
+                up <- liftIO $ fmap (either (const Nothing) Just)
+                  $ try @_ @SomeException $ canonicalizePath (binDir </> "ghcup" <.> exeExt)
+                when ((normalise <$> up) == Just (normalise ce)) $
+                  -- TODO: track cli arguments of previous invocation
+                  liftIO $ SPP.executeFile ce False ["tui"] Nothing
+                logInfo "Please restart 'ghcup' for the changes to take effect"
+              _ -> pure ()
+            pure $ Right ()
+          VRight (vi, _, _) -> do
+            forM_ (_viPostInstall =<< vi) $ \msg -> logInfo msg
+            logInfo "Please restart 'ghcup' for the changes to take effect"
             pure $ Right ()
           VLeft  (V (AlreadyInstalled _ _)) -> pure $ Right ()
           VLeft (V NoUpdate) -> pure $ Right ()
@@ -536,17 +556,7 @@ settings' = unsafePerformIO $ do
                                   , fileOutter    = \_ -> pure ()
                                   , fancyColors   = True
                                   }
-  newIORef $ AppState (Settings { cache      = True
-                                , noVerify   = False
-                                , keepDirs   = Never
-                                , downloader = Curl
-                                , verbose    = False
-                                , urlSource  = GHCupURL
-                                , noNetwork  = False
-                                , gpgSetting = GPGNone
-                                , noColor    = False
-                                , ..
-                                })
+  newIORef $ AppState defaultSettings
                       dirs
                       defaultKeyBindings
                       (GHCupInfo mempty mempty mempty)
@@ -605,4 +615,3 @@ getAppData mgi = runExceptT $ do
   flip runReaderT settings $ do
     lV <- listVersions Nothing Nothing
     pure $ BrickData (reverse lV)
-

app/ghcup/GHCup/OptParse.hs

@@ -67,6 +67,7 @@ data Options = Options
   -- global options
     optVerbose     :: Maybe Bool
   , optCache       :: Maybe Bool
+  , optMetaCache   :: Maybe Integer
   , optUrlSource   :: Maybe URI
   , optNoVerify    :: Maybe Bool
   , optKeepDirs    :: Maybe KeepDirs
@@ -105,6 +106,7 @@ opts =
   Options
     <$> invertableSwitch "verbose" 'v' False (help "Enable verbosity (default: disabled)")
     <*> invertableSwitch "cache" 'c' False (help "Cache downloads in ~/.ghcup/cache (default: disabled)")
+    <*> optional (option auto (long "metadata-caching" <> help "How long the yaml metadata caching interval is (in seconds), 0 to disable" <> internal))
     <*> optional
           (option
             (eitherReader parseUri)

app/ghcup/GHCup/OptParse/Common.hs

@@ -299,7 +299,7 @@ tagCompleter tool add = listIOCompleter $ do
         , fancyColors    = False
         }
   let appState = LeanAppState
-        (Settings True False Never Curl False GHCupURL True GPGNone False)
+        (defaultSettings { noNetwork = True })
         dirs'
         defaultKeyBindings
         loggerConfig
@@ -322,7 +322,7 @@ versionCompleter criteria tool = listIOCompleter $ do
         , fileOutter     = mempty
         , fancyColors    = False
         }
-  let settings = Settings True False Never Curl False GHCupURL True GPGNone False
+  let settings = defaultSettings { noNetwork = True }
   let leanAppState = LeanAppState
                    settings
                    dirs'
@@ -399,7 +399,7 @@ fromVersion' (SetToolVersion v) tool = do
     Right pvpIn ->
       lift (getLatestToolFor tool pvpIn dls) >>= \case
         Just (pvp_, vi') -> do
-          v' <- lift $ pvpToVersion pvp_
+          v' <- lift $ pvpToVersion pvp_ ""
           when (v' /= _tvVersion v) $ lift $ logWarn ("Assuming you meant version " <> prettyVer v')
           pure (GHCTargetVersion (_tvTarget v) v', Just vi')
         Nothing -> pure (v, vi)

app/ghcup/GHCup/OptParse/Config.hs

@@ -122,6 +122,7 @@ updateSettings config' settings = do
    mergeConf :: UserSettings -> Settings -> Settings
    mergeConf UserSettings{..} Settings{..} =
      let cache'      = fromMaybe cache uCache
+         metaCache'  = fromMaybe metaCache uMetaCache
          noVerify'   = fromMaybe noVerify uNoVerify
          keepDirs'   = fromMaybe keepDirs uKeepDirs
          downloader' = fromMaybe downloader uDownloader
@@ -129,7 +130,7 @@ updateSettings config' settings = do
          urlSource'  = fromMaybe urlSource uUrlSource
          noNetwork'  = fromMaybe noNetwork uNoNetwork
          gpgSetting' = fromMaybe gpgSetting uGPGSetting
-     in Settings cache' noVerify' keepDirs' downloader' verbose' urlSource' noNetwork' gpgSetting' noColor
+     in Settings cache' metaCache' noVerify' keepDirs' downloader' verbose' urlSource' noNetwork' gpgSetting' noColor
 
 
 

app/ghcup/GHCup/OptParse/DInfo.hs

@@ -51,7 +51,7 @@ describe_result = $( LitE . StringL <$>
                      runIO (do
                              CapturedProcess{..} <-  do
                               dirs <- liftIO getAllDirs
-                              let settings = AppState (Settings True False Never Curl False GHCupURL False GPGNone False)
+                              let settings = AppState (defaultSettings { noNetwork = True })
                                                dirs
                                                defaultKeyBindings
                               flip runReaderT settings $ executeOut "git" ["describe"] Nothing

app/ghcup/Main.hs

@@ -55,6 +55,7 @@ import qualified Data.ByteString               as B
 import qualified Data.Text                     as T
 import qualified Data.Text.IO                  as T
 import qualified Data.Text.Encoding            as E
+import qualified GHCup.Types                   as Types
 
 
 
@@ -72,15 +73,16 @@ toSettings options = do
  where
    mergeConf :: Options -> UserSettings -> Bool -> (Settings, KeyBindings)
    mergeConf Options{..} UserSettings{..} noColor =
-     let cache       = fromMaybe (fromMaybe False uCache) optCache
-         noVerify    = fromMaybe (fromMaybe False uNoVerify) optNoVerify
-         verbose     = fromMaybe (fromMaybe False uVerbose) optVerbose
-         keepDirs    = fromMaybe (fromMaybe Errors uKeepDirs) optKeepDirs
+     let cache       = fromMaybe (fromMaybe (Types.cache defaultSettings) uCache) optCache
+         metaCache   = fromMaybe (fromMaybe (Types.metaCache defaultSettings) uMetaCache) optMetaCache
+         noVerify    = fromMaybe (fromMaybe (Types.noVerify defaultSettings) uNoVerify) optNoVerify
+         verbose     = fromMaybe (fromMaybe (Types.verbose defaultSettings) uVerbose) optVerbose
+         keepDirs    = fromMaybe (fromMaybe (Types.keepDirs defaultSettings) uKeepDirs) optKeepDirs
          downloader  = fromMaybe (fromMaybe defaultDownloader uDownloader) optsDownloader
          keyBindings = maybe defaultKeyBindings mergeKeys uKeyBindings
-         urlSource   = maybe (fromMaybe GHCupURL uUrlSource) OwnSource optUrlSource
-         noNetwork   = fromMaybe (fromMaybe False uNoNetwork) optNoNetwork
-         gpgSetting  = fromMaybe (fromMaybe GPGNone uGPGSetting) optGpg
+         urlSource   = maybe (fromMaybe (Types.urlSource defaultSettings) uUrlSource) OwnSource optUrlSource
+         noNetwork   = fromMaybe (fromMaybe (Types.noNetwork defaultSettings) uNoNetwork) optNoNetwork
+         gpgSetting  = fromMaybe (fromMaybe (Types.gpgSetting defaultSettings) uGPGSetting) optGpg
      in (Settings {..}, keyBindings)
 #if defined(INTERNAL_DOWNLOADER)
    defaultDownloader = Internal

data/config.yaml

@@ -36,6 +36,10 @@ key-bindings:
   show-all-tools:
     KChar: 't'
 
+# The caching for the metadata files containing download info, depending on last access time
+# of the file. These usually are in '~/.ghcup/cache/ghcup-<ver>.yaml'.
+meta-cache: 300 # in seconds
+
 # Where to get GHC/cabal/hls download info/versions from. For more detailed explanation
 # check the 'URLSource' type in the code.
 url-source:

docs/guide.md

@@ -53,6 +53,25 @@ as e.g. `/etc/bash_completion.d/ghcup` (depending on distro)
 and make sure your bashrc sources the startup script
 (`/usr/share/bash-completion/bash_completion` on some distros).
 
+## Caching
+
+GHCup has a few caching mechanisms to avoid redownloads. All cached files end up in `~/.ghcup/cache` by default.
+
+### Downloads cache
+
+Downloaded tarballs (such as GHC, cabal, etc.) are not cached by default unless you pass `ghcup --cache` or set caching
+in your [config](#configuration) via `ghcup config set cache true`.
+
+### Metadata cache
+
+The metadata files (also see [github.com/haskell/ghcup-metadata](https://github.com/haskell/ghcup-metadata))
+have a 5 minutes cache per default depending on the last access time of the file. That means if you run
+`ghcup list` 10 times in a row, only the first time will trigger a download attempt.
+
+### Clearing the cache
+
+If you experience problems, consider clearing the cache via `ghcup gc --cache`.
+
 ## Compiling GHC from source
 
 Compiling from source is supported for both source tarballs and arbitrary git refs. See `ghcup compile ghc --help`

ghcup.cabal

@@ -224,6 +224,7 @@ executable ghcup
     , cabal-plan            ^>=0.7.2
     , containers            ^>=0.6
     , deepseq               ^>=1.4
+    , directory             ^>=1.3.6.0
     , filepath              ^>=1.4.2.1
     , ghcup
     , haskus-utils-variant  >=3.0      && <3.2
@@ -252,11 +253,13 @@ executable ghcup
     build-depends:
       , brick         ^>=0.64
       , transformers  ^>=0.5
+      , unix          ^>=2.7
       , vector        ^>=0.12
       , vty           >=5.28.2 && <5.34
 
   if os(windows)
     cpp-options: -DIS_WINDOWS
+
   if flag(no-exe)
     buildable: False
 

hie.yaml

@@ -4,7 +4,5 @@ cradle:
     path: ./lib
   - component: "ghcup:exe:ghcup"
     path: ./app/ghcup
-  - component: "ghcup:exe:ghcup-gen"
-    path: "./app/ghcup-gen"
   - component: "ghcup:test:ghcup-test"
     path: ./test

lib/GHCup.hs

@@ -1574,7 +1574,7 @@ listVersions lt' criteria = do
 
   currentGHCup :: Map.Map Version VersionInfo -> Maybe ListResult
   currentGHCup av =
-    let currentVer = fromJust $ pvpToVersion ghcUpVer
+    let currentVer = fromJust $ pvpToVersion ghcUpVer ""
         listVer    = Map.lookup currentVer av
         latestVer  = fst <$> headOf (getTagged Latest) av
         recommendedVer = fst <$> headOf (getTagged Latest) av
@@ -2576,7 +2576,7 @@ upgradeGHCup mtarget force' = do
 
   lift $ logInfo "Upgrading GHCup..."
   let latestVer = fromJust $ fst <$> getLatest dls GHCup
-  (Just ghcupPVPVer) <- pure $ pvpToVersion ghcUpVer
+  (Just ghcupPVPVer) <- pure $ pvpToVersion ghcUpVer ""
   when (not force' && (latestVer <= ghcupPVPVer)) $ throwE NoUpdate
   dli   <- liftE $ getDownloadInfo GHCup latestVer
   tmp   <- lift withGHCupTmpDir

lib/GHCup/Download.hs

@@ -242,14 +242,18 @@ getBase uri = do
     e <- liftIO $ doesFileExist json_file
     currentTime <- liftIO getCurrentTime
     Dirs { cacheDir } <- lift getDirs
+    Settings { metaCache } <- lift getSettings
 
        -- for local files, let's short-circuit and ignore access time
     if | scheme == "file" -> liftE $ download uri' Nothing Nothing cacheDir Nothing True
        | e -> do
-          accessTime <- liftIO $ getAccessTime json_file
-
+          accessTime <- fmap utcTimeToPOSIXSeconds $ liftIO $ getAccessTime json_file
+          let sinceLastAccess = utcTimeToPOSIXSeconds currentTime - accessTime
+          let cacheInterval = fromInteger metaCache
+          lift $ logDebug $ "last access was " <> T.pack (show sinceLastAccess) <> " ago, cache interval is " <> T.pack (show cacheInterval)
           -- access time won't work on most linuxes, but we can try regardless
-          if | ((utcTimeToPOSIXSeconds currentTime - utcTimeToPOSIXSeconds accessTime) > 300) ->
+          if | metaCache <= 0 -> dlWithMod currentTime json_file
+             | (sinceLastAccess > cacheInterval) ->
                 -- no access in last 5 minutes, re-check upstream mod time
                 dlWithMod currentTime json_file
              | otherwise -> pure json_file

lib/GHCup/Types.hs

@@ -294,6 +294,7 @@ instance NFData (URIRef Absolute) where
 
 data UserSettings = UserSettings
   { uCache       :: Maybe Bool
+  , uMetaCache   :: Maybe Integer
   , uNoVerify    :: Maybe Bool
   , uVerbose     :: Maybe Bool
   , uKeepDirs    :: Maybe KeepDirs
@@ -306,12 +307,13 @@ data UserSettings = UserSettings
   deriving (Show, GHC.Generic)
 
 defaultUserSettings :: UserSettings
-defaultUserSettings = UserSettings Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing
+defaultUserSettings = UserSettings Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing
 
 fromSettings :: Settings -> Maybe KeyBindings -> UserSettings
 fromSettings Settings{..} Nothing =
   UserSettings {
       uCache = Just cache
+    , uMetaCache = Just metaCache
     , uNoVerify = Just noVerify
     , uVerbose = Just verbose
     , uKeepDirs = Just keepDirs
@@ -335,6 +337,7 @@ fromSettings Settings{..} (Just KeyBindings{..}) =
             }
   in UserSettings {
       uCache = Just cache
+    , uMetaCache = Just metaCache
     , uNoVerify = Just noVerify
     , uVerbose = Just verbose
     , uKeepDirs = Just keepDirs
@@ -410,6 +413,7 @@ instance NFData LeanAppState
 
 data Settings = Settings
   { cache      :: Bool
+  , metaCache  :: Integer
   , noVerify   :: Bool
   , keepDirs   :: KeepDirs
   , downloader :: Downloader
@@ -421,6 +425,12 @@ data Settings = Settings
   }
   deriving (Show, GHC.Generic)
 
+defaultMetaCache :: Integer
+defaultMetaCache = 300 -- 5 minutes
+
+defaultSettings :: Settings
+defaultSettings = Settings False defaultMetaCache False Never Curl False GHCupURL False GPGNone False
+
 instance NFData Settings
 
 data Dirs = Dirs

lib/GHCup/Utils.hs

@@ -59,6 +59,7 @@ import           Control.Monad.Reader
 import           Control.Monad.Trans.Resource
                                          hiding ( throwM )
 import           Control.Monad.IO.Unlift        ( MonadUnliftIO( withRunInIO ) )
+import           Data.Bifunctor                 ( first )
 import           Data.ByteString                ( ByteString )
 import           Data.Either
 import           Data.Foldable
@@ -110,8 +111,8 @@ import qualified Data.List.NonEmpty            as NE
 -- >>> import Text.PrettyPrint.HughesPJClass ( prettyShow )
 -- >>> let lc = LoggerConfig { lcPrintDebug = False, consoleOutter = mempty, fileOutter = mempty, fancyColors = False }
 -- >>> dirs' <- getAllDirs
--- >>> let installedVersions = [ ([pver|8.10.7|], Nothing), ([pver|8.10.4|], Nothing), ([pver|8.8.4|], Nothing), ([pver|8.8.3|], Nothing) ]
--- >>> let settings = Settings True False Never Curl False GHCupURL True GPGNone False
+-- >>> let installedVersions = [ ([pver|8.10.7|], "-debug+lol", Nothing), ([pver|8.10.4|], "", Nothing), ([pver|8.8.4|], "", Nothing), ([pver|8.8.3|], "", Nothing) ]
+-- >>> let settings = Settings True 0 False Never Curl False GHCupURL True GPGNone False
 -- >>> let leanAppState = LeanAppState settings dirs' defaultKeyBindings lc
 -- >>> cwd <- getCurrentDirectory
 -- >>> (Right ref) <- pure $ parseURI strictURIParserOptions $ "file://" <> E.encodeUtf8 (T.pack cwd) <> "/data/metadata/" <> (urlBaseName . view pathL' $ ghcupURL)
@@ -631,34 +632,34 @@ getGHCForPVP pvpIn mt = do
   ghcs <- rights <$> getInstalledGHCs
   -- we're permissive here... failed parse just means we have no match anyway
   let ghcs' = catMaybes $ flip fmap ghcs $ \GHCTargetVersion{..} -> do
-        pvp_ <- versionToPVP _tvVersion
-        pure (pvp_, _tvTarget)
+        (pvp_, rest) <- versionToPVP _tvVersion
+        pure (pvp_, rest, _tvTarget)
 
   getGHCForPVP' pvpIn ghcs' mt
 
 -- | Like 'getGHCForPVP', except with explicit input parameter.
 --
--- >>> fmap prettyShow $ getGHCForPVP' [pver|8|] installedVersions Nothing
--- "Just 8.10.7"
+-- >>> getGHCForPVP' [pver|8|] installedVersions Nothing
+-- Just (GHCTargetVersion {_tvTarget = Nothing, _tvVersion = Version {_vEpoch = Nothing, _vChunks = (Digits 8 :| []) :| [Digits 10 :| [],Digits 7 :| []], _vRel = [Str "debug" :| []], _vMeta = Just "lol"}})
 -- >>> fmap prettyShow $ getGHCForPVP' [pver|8.8|] installedVersions Nothing
 -- "Just 8.8.4"
 -- >>> fmap prettyShow $ getGHCForPVP' [pver|8.10.4|] installedVersions Nothing
 -- "Just 8.10.4"
 getGHCForPVP' :: MonadThrow m
              => PVP
-             -> [(PVP, Maybe Text)] -- ^ installed GHCs
+             -> [(PVP, Text, Maybe Text)] -- ^ installed GHCs
              -> Maybe Text          -- ^ the target triple
              -> m (Maybe GHCTargetVersion)
 getGHCForPVP' pvpIn ghcs' mt = do
   let mResult = lastMay
-                  . sortBy (\(x, _) (y, _) -> compare x y)
+                  . sortBy (\(x, _, _) (y, _, _) -> compare x y)
                   . filter
-                      (\(pvp_, target) ->
+                      (\(pvp_, _, target) ->
                         target == mt && matchPVPrefix pvp_ pvpIn
                       )
                   $ ghcs'
-  forM mResult $ \(pvp_, target) -> do
-    ver' <- pvpToVersion pvp_
+  forM mResult $ \(pvp_, rest, target) -> do
+    ver' <- pvpToVersion pvp_ rest
     pure (GHCTargetVersion target ver')
 
 
@@ -679,7 +680,7 @@ getLatestToolFor :: MonadThrow m
 getLatestToolFor tool pvpIn dls = do
   let ls = fromMaybe [] $ preview (ix tool % to Map.toDescList) dls
   let ps = catMaybes $ fmap (\(v, vi) -> (,vi) <$> versionToPVP v) ls
-  pure . headMay . filter (\(v, _) -> matchPVPrefix pvpIn v) $ ps
+  pure . fmap (first fst) . headMay . filter (\((v, _), _) -> matchPVPrefix pvpIn v) $ ps
 
 
 

lib/GHCup/Utils/Prelude.hs

@@ -44,7 +44,7 @@ import           Control.Monad.IO.Class
 import           Control.Monad.Reader
 import           Data.Bifunctor
 import           Data.ByteString                ( ByteString )
-import           Data.List                      ( nub, intercalate, stripPrefix, isPrefixOf, dropWhileEnd )
+import           Data.List                      ( nub, intercalate, stripPrefix, isPrefixOf, dropWhileEnd, intersperse )
 import           Data.Maybe
 import           Data.Foldable
 import           Data.List.NonEmpty             ( NonEmpty( (:|) ))
@@ -313,18 +313,46 @@ removeLensFieldLabel str' =
   maybe str' T.unpack . T.stripPrefix (T.pack "_") . T.pack $ str'
 
 
-pvpToVersion :: MonadThrow m => PVP -> m Version
-pvpToVersion =
-  either (\_ -> throwM $ ParseError "Couldn't convert PVP to Version") pure . version . prettyPVP
+pvpToVersion :: MonadThrow m => PVP -> Text -> m Version
+pvpToVersion pvp_ rest =
+  either (\_ -> throwM $ ParseError "Couldn't convert PVP to Version") pure . version . (<> rest) . prettyPVP $ pvp_
 
-versionToPVP :: MonadThrow m => Version -> m PVP
-versionToPVP v = either (\_ -> alternative v) pure . pvp . prettyVer $ v
+-- | Convert a version to a PVP and unparsable rest.
+--
+-- -- prop> \v -> let (Just (pvp', r)) = versionToPVP v in pvpToVersion pvp' r === Just v
+versionToPVP :: MonadThrow m => Version -> m (PVP, Text)
+versionToPVP (Version (Just _) _ _ _) = throwM $ ParseError "Unexpected epoch"
+versionToPVP v = either (\_ -> (, rest v) <$> alternative v) (pure . (, mempty)) . pvp . prettyVer $ v
  where
   alternative :: MonadThrow m => Version -> m PVP
   alternative v' = case NE.takeWhile isDigit (_vChunks v') of
     [] -> throwM $ ParseError "Couldn't convert Version to PVP"
     xs -> pure $ pvpFromList (unsafeDigit <$> xs)
 
+  rest :: Version -> Text
+  rest (Version _ cs pr me) =
+    let chunks = NE.dropWhile isDigit cs
+        ver = intersperse (T.pack ".") . chunksAsT $ chunks
+        me' = maybe [] (\m -> [T.pack "+",m]) me
+        pr' = foldable [] (T.pack "-" :) $ intersperse (T.pack ".") (chunksAsT pr)
+        prefix = case (ver, pr', me') of
+                   ((_:_), _, _) -> T.pack "."
+                   _             -> T.pack ""
+    in prefix <> mconcat (ver <> pr' <> me')
+   where
+    chunksAsT :: Functor t => t VChunk -> t Text
+    chunksAsT = fmap (foldMap f)
+      where
+        f :: VUnit -> Text
+        f (Digits i) = T.pack $ show i
+        f (Str s)    = s
+
+    foldable :: Foldable f => f b -> (f a -> f b) -> f a -> f b
+    foldable d g f | null f    = d
+                   | otherwise = g f
+
+
+
   isDigit :: VChunk -> Bool
   isDigit (Digits _ :| []) = True
   isDigit _                = False

test/GHCup/Types/JSONSpec.hs

@@ -3,7 +3,7 @@
 module GHCup.Types.JSONSpec where
 
 import           GHCup.ArbitraryTypes ()
-import           GHCup.Types
+import           GHCup.Types hiding ( defaultSettings )
 import           GHCup.Types.JSON ()
 
 import           Test.Aeson.GenericSpecs