Add --metadata-fetching-mode arg, fixes #440

app/ghcup/GHCup/OptParse.hs

@@ -67,13 +67,13 @@ import           URI.ByteString
 import qualified Data.ByteString.UTF8          as UTF8
 
 
-
 data Options = Options
   {
   -- global options
     optVerbose     :: Maybe Bool
   , optCache       :: Maybe Bool
   , optMetaCache   :: Maybe Integer
+  , optMetaMode    :: Maybe MetaMode
   , optPlatform    :: Maybe PlatformRequest
   , optUrlSource   :: Maybe URI
   , optNoVerify    :: Maybe Bool
@@ -117,6 +117,7 @@ opts =
     <$> invertableSwitch "verbose" (Just 'v') False (help "Enable verbosity (default: disabled)")
     <*> invertableSwitch "cache" (Just '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 auto (long "metadata-fetching-mode" <> metavar "<Strict|Lax>" <> help "Whether to fail on metadata download failure (Strict) or fall back to cached version (Lax (default))"))
     <*> optional
       (option
         (eitherReader platformParser)

app/ghcup/GHCup/OptParse/Config.hs

@@ -124,6 +124,7 @@ updateSettings :: UserSettings -> Settings -> Settings
 updateSettings UserSettings{..} Settings{..} =
    let cache'      = fromMaybe cache uCache
        metaCache'  = fromMaybe metaCache uMetaCache
+       metaMode'   = fromMaybe metaMode uMetaMode
        noVerify'   = fromMaybe noVerify uNoVerify
        keepDirs'   = fromMaybe keepDirs uKeepDirs
        downloader' = fromMaybe downloader uDownloader
@@ -132,7 +133,7 @@ updateSettings UserSettings{..} Settings{..} =
        noNetwork'  = fromMaybe noNetwork uNoNetwork
        gpgSetting' = fromMaybe gpgSetting uGPGSetting
        platformOverride' = uPlatformOverride <|> platformOverride
-   in Settings cache' metaCache' noVerify' keepDirs' downloader' verbose' urlSource' noNetwork' gpgSetting' noColor platformOverride'
+   in Settings cache' metaCache' metaMode' noVerify' keepDirs' downloader' verbose' urlSource' noNetwork' gpgSetting' noColor platformOverride'
 
 
 

app/ghcup/Main.hs

@@ -79,6 +79,7 @@ toSettings options = do
    mergeConf Options{..} UserSettings{..} noColor =
      let cache       = fromMaybe (fromMaybe (Types.cache defaultSettings) uCache) optCache
          metaCache   = fromMaybe (fromMaybe (Types.metaCache defaultSettings) uMetaCache) optMetaCache
+         metaMode    = fromMaybe (fromMaybe (Types.metaMode defaultSettings) uMetaMode) optMetaMode
          noVerify    = fromMaybe (fromMaybe (Types.noVerify defaultSettings) uNoVerify) optNoVerify
          verbose     = fromMaybe (fromMaybe (Types.verbose defaultSettings) uVerbose) optVerbose
          keepDirs    = fromMaybe (fromMaybe (Types.keepDirs defaultSettings) uKeepDirs) optKeepDirs

data/config.yaml

@@ -40,6 +40,12 @@ key-bindings:
 # of the file. These usually are in '~/.ghcup/cache/ghcup-<ver>.yaml'.
 meta-cache: 300 # in seconds
 
+# When trying to download ghcup metadata, this option decides what to do
+# when the download fails:
+#   1. Lax: use existing ~/.ghcup/cache/ghcup-<ver>.yaml as fallback (default)
+#   2. Strict: fail hard
+meta-mode: Lax # Strict | Lax
+
 # Where to get GHC/cabal/hls download info/versions from. For more detailed explanation
 # check the 'URLSource' type in the code.
 url-source:

lib/GHCup/Download.hs

@@ -162,17 +162,21 @@ getBase :: ( MonadReader env m
            , MonadMask m
            )
         => URI
-        -> Excepts '[GPGError, DigestError, JSONError, FileDoesNotExistError] m GHCupInfo
+        -> Excepts '[DownloadFailed, GPGError, DigestError, JSONError, FileDoesNotExistError] m GHCupInfo
 getBase uri = do
-  Settings { noNetwork, downloader } <- lift getSettings
+  Settings { noNetwork, downloader, metaMode } <- lift getSettings
 
   -- try to download yaml... usually this writes it into cache dir,
   -- but in some cases not (e.g. when using file://), so we honour
   -- the return filepath, if any
   mYaml <- if noNetwork && view (uriSchemeL' % schemeBSL') uri /= "file" -- for file://, let it fall through
            then pure Nothing
-           else handleIO (\e -> lift (warnCache (displayException e) downloader) >> pure Nothing)
+           else handleIO (\e -> case metaMode of
-               . catchE @_ @_ @'[] (\e@(DownloadFailed _) -> lift (warnCache (prettyShow e) downloader) >> pure Nothing)
+                                  Strict -> throwIO e
+                                  Lax -> lift (warnCache (displayException e) downloader) >> pure Nothing)
+               . catchE @_ @_ @'[DownloadFailed] (\e@(DownloadFailed _) -> case metaMode of
+                   Strict -> throwE e
+                   Lax -> lift (warnCache (prettyShow e) downloader) >> pure Nothing)
                . fmap Just
                . smartDl
                $ uri

lib/GHCup/Types.hs

@@ -297,10 +297,16 @@ instance NFData URLSource
 instance NFData (URIRef Absolute) where
   rnf (URI !_ !_ !_ !_ !_) = ()
 
+data MetaMode = Strict
+              | Lax
+  deriving (Show, Read, Eq, GHC.Generic)
+
+instance NFData MetaMode
 
 data UserSettings = UserSettings
   { uCache       :: Maybe Bool
   , uMetaCache   :: Maybe Integer
+  , uMetaMode    :: Maybe MetaMode
   , uNoVerify    :: Maybe Bool
   , uVerbose     :: Maybe Bool
   , uKeepDirs    :: Maybe KeepDirs
@@ -314,13 +320,14 @@ data UserSettings = UserSettings
   deriving (Show, GHC.Generic)
 
 defaultUserSettings :: UserSettings
-defaultUserSettings = UserSettings Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing
+defaultUserSettings = UserSettings Nothing Nothing 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
+    , uMetaMode = Just metaMode
     , uNoVerify = Just noVerify
     , uVerbose = Just verbose
     , uKeepDirs = Just keepDirs
@@ -346,6 +353,7 @@ fromSettings Settings{..} (Just KeyBindings{..}) =
   in UserSettings {
       uCache = Just cache
     , uMetaCache = Just metaCache
+    , uMetaMode = Just metaMode
     , uNoVerify = Just noVerify
     , uVerbose = Just verbose
     , uKeepDirs = Just keepDirs
@@ -426,6 +434,7 @@ instance NFData LeanAppState
 data Settings = Settings
   { cache            :: Bool
   , metaCache        :: Integer
+  , metaMode         :: MetaMode
   , noVerify         :: Bool
   , keepDirs         :: KeepDirs
   , downloader       :: Downloader
@@ -442,7 +451,7 @@ defaultMetaCache :: Integer
 defaultMetaCache = 300 -- 5 minutes
 
 defaultSettings :: Settings
-defaultSettings = Settings False defaultMetaCache False Never Curl False GHCupURL False GPGNone False Nothing
+defaultSettings = Settings False defaultMetaCache Lax False Never Curl False GHCupURL False GPGNone False Nothing
 
 instance NFData Settings
 

lib/GHCup/Types/JSON.hs

@@ -43,6 +43,7 @@ import qualified Text.Megaparsec               as MP
 import qualified Text.Megaparsec.Char          as MPC
 
 
+deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''MetaMode
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''Architecture
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''LinuxDistro
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''VSep