Print better error on 'ghcup <command> <tool>-<version>'

Wrt #180

lib/GHCup/Download.hs

@@ -296,7 +296,7 @@ getDownloadInfo' :: ( MonadReader env m
                       m
                       DownloadInfo
 getDownloadInfo' t v = do
-  (PlatformRequest a p mv) <- lift getPlatformReq
+  pfreq@(PlatformRequest a p mv) <- lift getPlatformReq
   GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
 
   let distro_preview f g =
@@ -317,7 +317,7 @@ getDownloadInfo' t v = do
       without_distro     = distro_preview (set _Linux UnknownLinux) (const Nothing)
 
   maybe
-    (throwE NoDownload)
+    (throwE $ NoDownload v t (Just pfreq))
     pure
     (case p of
       -- non-musl won't work on alpine

lib/GHCup/Errors.hs

@@ -206,12 +206,26 @@ instance HFErrorProject NoCompatiblePlatform where
   eDesc _ = "No compatible platform could be found"
 
 -- | Unable to find a download for the requested version/distro.
-data NoDownload = NoDownload
+data NoDownload = NoDownload GHCTargetVersion Tool (Maybe PlatformRequest)
+                | NoDownload' GlobalTool
   deriving Show
 
 instance Pretty NoDownload where
-  pPrint NoDownload =
-    text (eDesc (Proxy :: Proxy NoDownload))
+  pPrint (NoDownload tver@(GHCTargetVersion mtarget vv) tool mpfreq)
+    | (Just target) <- mtarget
+    , target `elem` (T.pack . prettyShow <$> enumFromTo (minBound :: Tool) (maxBound :: Tool))
+    = text $ "Unable to find a download for "
+             <> show tool
+             <> " version '"
+             <> T.unpack (tVerToText tver)
+             <> maybe "'\n" (\pfreq -> "' on detected platform " <> pfReqToString pfreq <> "\n") mpfreq
+             <> "Perhaps you meant: 'ghcup <command> "
+             <> T.unpack target
+             <> " "
+             <> T.unpack (prettyVer vv)
+             <> "'"
+    | otherwise = text $ "Unable to find a download for " <> T.unpack (tVerToText tver)
+  pPrint (NoDownload' globalTool) = text $ "Unable to find a download for " <> prettyShow globalTool
 
 instance HFErrorProject NoDownload where
   eBase _ = 10

lib/GHCup/GHC.hs

@@ -125,7 +125,7 @@ testGHCVer ver addMakeArgs = do
 
   dlInfo <-
     preview (ix GHC % ix ver % viTestDL % _Just) dls
-      ?? NoDownload
+      ?? NoDownload ver GHC Nothing
 
   liftE $ testGHCBindist dlInfo ver addMakeArgs
 
@@ -260,7 +260,7 @@ fetchGHCSrc v mfp = do
   GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
   dlInfo <-
     preview (ix GHC % ix v % viSourceDL % _Just) dls
-      ?? NoDownload
+      ?? NoDownload v GHC Nothing
   liftE $ downloadCached' dlInfo Nothing mfp
 
 
@@ -818,7 +818,7 @@ compileGHC :: ( MonadMask m
                 GHCTargetVersion
 compileGHC targetGhc crossTarget ov bstrap jobs mbuildConfig patches aargs buildFlavour buildSystem installDir
   = do
-    PlatformRequest { .. } <- lift getPlatformReq
+    pfreq@PlatformRequest { .. } <- lift getPlatformReq
     GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
 
     (workdir, tmpUnpack, tver) <- case targetGhc of
@@ -827,9 +827,10 @@ compileGHC targetGhc crossTarget ov bstrap jobs mbuildConfig patches aargs build
         lift $ logDebug $ "Requested to compile: " <> prettyVer ver <> " with " <> either prettyVer T.pack bstrap
 
         -- download source tarball
+        let tver = mkTVer ver
         dlInfo <-
-          preview (ix GHC % ix (mkTVer ver) % viSourceDL % _Just) dls
-            ?? NoDownload
+          preview (ix GHC % ix tver % viSourceDL % _Just) dls
+            ?? NoDownload tver GHC (Just pfreq)
         dl <- liftE $ downloadCached dlInfo Nothing
 
         -- unpack
@@ -1303,7 +1304,7 @@ compileGHC targetGhc crossTarget ov bstrap jobs mbuildConfig patches aargs build
 
   bghc = case bstrap of
            Right g    -> g
-           Left  bver -> ("ghc-" <> (T.unpack . prettyVer $ bver) <> exeExt)
+           Left  bver -> "ghc-" <> (T.unpack . prettyVer $ bver) <> exeExt
 
 
 

lib/GHCup/HLS.hs

@@ -354,7 +354,7 @@ compileHLS :: ( MonadMask m
                        , NotInstalled
                        ] m Version
 compileHLS targetHLS ghcs jobs ov installDir cabalProject cabalProjectLocal updateCabal patches cabalArgs = do
-  PlatformRequest { .. } <- lift getPlatformReq
+  pfreq@PlatformRequest { .. } <- lift getPlatformReq
   GHCupInfo { _ghcupDownloads = dls } <- lift getGHCupInfo
   Dirs { .. } <- lift getDirs
 
@@ -370,7 +370,7 @@ compileHLS targetHLS ghcs jobs ov installDir cabalProject cabalProjectLocal upda
       -- download source tarball
       dlInfo <-
         preview (ix HLS % ix (mkTVer tver) % viSourceDL % _Just) dls
-          ?? NoDownload
+          ?? NoDownload (mkTVer tver) HLS (Just pfreq)
       dl <- liftE $ downloadCached dlInfo Nothing
 
       -- unpack

lib/GHCup/Types.hs

@@ -132,6 +132,9 @@ data GlobalTool = ShimGen
 
 instance NFData GlobalTool
 
+instance Pretty GlobalTool where
+  pPrint ShimGen = text "shimgen"
+
 
 -- | All necessary information of a tool version, including
 -- source download and per-architecture downloads.

lib/GHCup/Utils.hs

@@ -1212,7 +1212,7 @@ ensureGlobalTools
       (GHCupInfo _ _ gTools) <- lift getGHCupInfo
       dirs <- lift getDirs
       shimDownload <- liftE $ lE @_ @'[NoDownload]
-        $ maybe (Left NoDownload) Right $ Map.lookup ShimGen gTools
+        $ maybe (Left (NoDownload' ShimGen)) Right $ Map.lookup ShimGen gTools
       let dl = downloadCached' shimDownload (Just "gs.exe") Nothing
       void $ (\DigestError{} -> do
           lift $ logWarn "Digest doesn't match, redownloading gs.exe..."