Fix error handling when we can't find a filename

2021-08-06 19:45:59 +02:00
8 changed files with 54 additions and 198 deletions
--- a/README.md
+++ b/README.md
@@ -19,8 +19,6 @@ Similar in scope to [rustup](https://github.com/rust-lang-nursery/rustup.rs), [p
     * [Env variables](#env-variables)
     * [Installing custom bindists](#installing-custom-bindists)
     * [Tips and tricks](#tips-and-tricks)
-     * [Stack hooks](#stack-hooks)
-     * [Sharing MSys2 between stack and ghcup](#sharing-msys2-between-stack-and-ghcup)
   * [Design goals](#design-goals)
   * [How](#how)
   * [Known users](#known-users)
@@ -141,10 +139,6 @@ This is the complete list of env variables that change GHCup behavior:
 * `GHCUP_SKIP_UPDATE_CHECK`: Skip the (possibly annoying) update check when you run a command
 * `CC`/`LD` etc.: full environment is passed to the build system when compiling GHC via GHCup

-On windows, there are additional variables:
-
-* `GHCUP_MSYS2`: where to find msys2, so we can invoke shells and other cool stuff
-
 ### Installing custom bindists

 There are a couple of good use cases to install custom bindists:
@@ -208,36 +202,6 @@ with_ghc 8.10.5 code path/to/haskell/source
 Cabal and HLS will now see `8.10.5` as the primary GHC, without the need to
 run `ghcup set` all the time when switching between projects.

-### Stack hooks
-
-GHCup distributes a patched Stack, which has support for custom installation hooks, see:
-
-* https://github.com/commercialhaskell/stack/pull/5585
-
-Usually, the bootstrap script will already install a hook for you. If not,
-download it [here](https://gitlab.haskell.org/haskell/ghcup-hs/-/tree/master/hooks/stack/ghc-install.sh),
-place it in `~/.stack/hooks/ghc-install.sh` and make sure it's executable.
-
-Hooks aren't run when `system-ghc: true` is set in `stack.yaml`. If you want stack
-to never fall back to its own installation logic if ghcup fails, run the following command:
-
-```sh
-stack config set install-ghc false --global
-```
-
-### Sharing MSys2 between stack and ghcup
-
-You can tell stack to use GHCup's MSys2 installation. Add the following lines to `~/.stack/config.yaml`:
-
-```yml
-skip-msys: true
-extra-path:
-  - "C:\\ghcup\\msys64\\usr\\bin"
-  - "C:\\ghcup\\msys64\\mingw64\\bin"
-extra-include-dirs: "C:\\ghcup\\msys64\\mingw64\\include"
-extra-lib-dirs: "C:\\ghcup\\msys64\\mingw64\\lib"
-```
-
 ## Design goals

 1. simplicity
@@ -314,6 +278,18 @@ to figure out whether you have the correct toolchain and
 the correct dependencies. Refer to [the official docs](https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Linux)
 on how to prepare your environment for building GHC.

+### Stack support
+
+There may be a number of bugs when trying to make ghcup installed GHC versions work with stack,
+such as:
+
+- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/188
+
+Further, stack's upgrade procedure may break/confuse ghcup. There are a number of integration
+issues discussed here:
+
+- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/153
+
 ### Windows support

 Windows support is in early stages. Since windows doesn't support symbolic links properly,
--- a/app/ghcup-gen/Validate.hs
+++ b/app/ghcup-gen/Validate.hs
@@ -237,7 +237,7 @@ validateTarballs (TarballFilter etool versionRegex) dls gt = do
                  ($(logError) $ T.pack $ prettyShow e)
                liftIO $ exitWith (ExitFailure 2)

-    let appstate = AppState (Settings True False Never Curl False GHCupURL False) dirs defaultKeyBindings (GHCupInfo mempty mempty mempty) pfreq
+    let appstate = AppState (Settings True False Never Curl True GHCupURL False) dirs defaultKeyBindings (GHCupInfo mempty mempty mempty) pfreq

    r <-
      runLogger
--- a/42
+++ b/42
@@ -8,7 +8,6 @@
 #   * BOOTSTRAP_HASKELL_GHC_VERSION - the ghc version to install
 #   * BOOTSTRAP_HASKELL_CABAL_VERSION - the cabal version to install
 #   * BOOTSTRAP_HASKELL_INSTALL_STACK - whether to install latest stack
-#   * BOOTSTRAP_HASKELL_INSTALL_STACK_HOOK - whether to install stack hook as well
 #   * BOOTSTRAP_HASKELL_INSTALL_HLS - whether to install latest hls
 #   * BOOTSTRAP_HASKELL_ADJUST_BASHRC - whether to adjust PATH in bashrc (prepend)
 #   * BOOTSTRAP_HASKELL_ADJUST_CABAL_CONFIG - whether to adjust mingw paths in cabal.config on windows
@@ -509,25 +508,17 @@ ask_hls() {

 ask_stack() {
 	if [ -n "${BOOTSTRAP_HASKELL_INSTALL_STACK}" ] ; then
-		if [ -n "${BOOTSTRAP_HASKELL_INSTALL_STACK_HOOK}" ] ; then
-			return 2
-		else
-			return 1
-		fi
+		return 1
 	fi

 	if [ -z "${BOOTSTRAP_HASKELL_NONINTERACTIVE}" ] ; then
 		echo "-------------------------------------------------------------------------------"

-		warn "Do you want to install stack and stack hooks?"
-		warn ""
+		warn "Do you want to install stack?"
 		warn "Stack is a haskell build tool similar to cabal that is used by some projects."
 		warn "Also see https://docs.haskellstack.org/"
 		warn ""
-		warn "Stack hooks allow stack to use ghcup for GHC installation (usually stack handles"
-		warn "installation itself, leading to possibly duplicated GHC versions)."
-		warn ""
-		warn "[Y] Yes, with hooks  [L] Yes, no hooks  [N] No  [?] Help (default is \"N\")."
+		warn "[Y] Yes  [N] No  [?] Help (default is \"N\")."
 		warn ""

 		while true; do
@@ -535,16 +526,13 @@ ask_stack() {

 			case $stack_answer in
 				[Yy]*)
-					return 2 ;;
-				[Ll]*)
 					return 1 ;;
 				[Nn]* | "")
 					return 0 ;;
 				*)
 					echo "Possible choices are:"
 					echo
-					echo "Y - Yes, install stack with hooks"
-					echo "L - Yes, install stack without hooks"
+					echo "Y - Yes, install stack"
 					echo "N - No, don't install anything more (default)"
 					echo
 					echo "Please make your choice and press ENTER."
@@ -648,27 +636,7 @@ esac

 case $ask_stack_answer in
 	1)
-		{
-			_eghcup --cache install stack
-			edo stack update
-		} || warn "Stack installation failed, continuing anyway"
-		;;
-	2)
-		{
-			_eghcup --cache install stack
-		    edo stack update
-			if [ -n "${STACK_ROOT}" ] ; then
-				stack_root=$STACK_ROOT
-			else
-				stack_root=${HOME}/.stack
-			fi
-			edo mkdir -p "${stack_root}/hooks/"
-			edo curl -Lf "https://www.haskell.org/ghcup/sh/hooks/stack/ghc-install.sh" > "${stack_root}/hooks/ghc-install.sh"
-			edo chmod +x "${stack_root}/hooks/ghc-install.sh"
-			edo stack config set system-ghc  false --global
-			edo stack config set install-ghc false --global
-
-		} || warn "Stack installation failed, continuing anyway"
+		_eghcup --cache install stack || warn "Stack installation failed, continuing anyway"
 		;;
 	*) ;;
 esac
--- a/bootstrap-haskell.ps1
+++ b/bootstrap-haskell.ps1
@@ -29,8 +29,6 @@ param (
    [switch]$InBash,
    # Whether to install stack as well
    [switch]$InstallStack,
-    # Whether to install stack hooks as well
-    [switch]$InstallStackHook,
    # Whether to install hls as well
    [switch]$InstallHLS,
    # Skip adjusting cabal.config with mingw paths
@@ -225,7 +223,6 @@ $null = [Environment]::SetEnvironmentVariable("GHCUP_INSTALL_BASE_PREFIX", $Ghcu


 $GhcupDir = ('{0}\ghcup' -f $GhcupBasePrefix)
-$StackDir = ('{0}\sr' -f $GhcupBasePrefix)
 $MsysDir = ('{0}\msys64' -f $GhcupDir)
 $Bash = ('{0}\usr\bin\bash' -f $MsysDir)
 if (!($BootstrapUrl)) {
@@ -313,28 +310,15 @@ if (!($InstallHLS)) {
 }

 # ask whether to install stack
-$InstallStackDoc = @'
-Do you want to install stack and stack hooks?
-
-Stack is a haskell build tool similar to cabal that is used by some projects.
-Also see https://docs.haskellstack.org/
-
-Stack hooks allow stack to use ghcup for GHC installation (usually stack handles
-installation itself, leading to possibly duplicated GHC versions).
-'@
 if (!($InstallStack)) {
  if (!($Silent)) {
    $StackDecision = $Host.UI.PromptForChoice('Install stack'
-      , $InstallStackDoc
-      , [System.Management.Automation.Host.ChoiceDescription[]] @('&Yes, with hooks'
-          '&Light install, without hooks'
+      , 'Do you want to install stack as well?'
+      , [System.Management.Automation.Host.ChoiceDescription[]] @('&Yes'
          '&No'
-          '&Abort'), 2)
+          '&Abort'), 1)

    if ($StackDecision -eq 0) {
-      $InstallStack = $true
-	  $InstallStackHook = $true
-    } elseif ($StackDecision -eq 1) {
      $InstallStack = $true
    } elseif ($StackDecision -eq 2) {
      Exit 0
@@ -515,11 +499,6 @@ $SilentExport = 'export BOOTSTRAP_HASKELL_NONINTERACTIVE=1 ;'

 if ($InstallStack) {
  $StackInstallExport = 'export BOOTSTRAP_HASKELL_INSTALL_STACK=1 ;'
-  $null = [Environment]::SetEnvironmentVariable("STACK_ROOT", $StackDir, [System.EnvironmentVariableTarget]::User)
-}
-
-if ($InstallStackHook) {
-  $StackInstallHookExport = 'export BOOTSTRAP_HASKELL_INSTALL_STACK_HOOK=1 ;'
 }

 if ($InstallHLS) {
@@ -531,9 +510,9 @@ if (!($NoAdjustCabalConfig)) {
 }

 if ((Get-Process -ID $PID).ProcessName.StartsWith("bootstrap-haskell") -Or $InBash) {
-  Exec "$Bash" '-lc' ('{4} {6} {7} {8} {9} [ -n ''{1}'' ] && export GHCUP_MSYS2=$(cygpath -m ''{1}'') ; [ -n ''{2}'' ] && export GHCUP_INSTALL_BASE_PREFIX=$(cygpath -m ''{2}/'') ; export PATH=$(cygpath -u ''{3}/bin''):$PATH ; export CABAL_DIR=''{5}'' ; export STACK_ROOT=$(cygpath -m ''{10}/'') ; [[ ''{0}'' = https* ]]  && curl --proto ''=https'' --tlsv1.2 -sSf {0} | bash || cat $(cygpath -m ''{0}'') | bash' -f $BootstrapUrl, $MsysDir, $GhcupBasePrefix, $GhcupDir, $SilentExport, $CabalDirFull, $StackInstallExport, $HLSInstallExport, $AdjustCabalConfigExport, $StackInstallHookExport, $StackDir)
+  Exec "$Bash" '-lc' ('{4} {6} {7} {8} [ -n ''{1}'' ] && export GHCUP_MSYS2=$(cygpath -m ''{1}'') ; [ -n ''{2}'' ] && export GHCUP_INSTALL_BASE_PREFIX=$(cygpath -m ''{2}/'') ; export PATH=$(cygpath -u ''{3}/bin''):$PATH ; export CABAL_DIR=''{5}'' ; [[ ''{0}'' = https* ]]  && curl --proto ''=https'' --tlsv1.2 -sSf {0} | bash || cat $(cygpath -m ''{0}'') | bash' -f $BootstrapUrl, $MsysDir, $GhcupBasePrefix, $GhcupDir, $SilentExport, $CabalDirFull, $StackInstallExport, $HLSInstallExport, $AdjustCabalConfigExport)
 } else {
-  Exec "$Msys2Shell" '-mingw64' '-mintty' '-c' ('{4} {6} {7} {8} {9} [ -n ''{1}'' ] && export GHCUP_MSYS2=$(cygpath -m ''{1}'') ; [ -n ''{2}'' ] && export GHCUP_INSTALL_BASE_PREFIX=$(cygpath -m ''{2}/'') ; export PATH=$(cygpath -u ''{3}/bin''):$PATH ; export CABAL_DIR=''{5}'' ; export STACK_ROOT=$(cygpath -m ''{10}/'') ; trap ''echo Press any key to exit && read -n 1 && exit'' 2 ; [[ ''{0}'' = https* ]]  && curl --proto ''=https'' --tlsv1.2 -sSf {0} | bash || cat $(cygpath -m ''{0}'') | bash ; echo ''Press any key to exit'' && read -n 1' -f $BootstrapUrl, $MsysDir, $GhcupBasePrefix, $GhcupDir, $SilentExport, $CabalDirFull, $StackInstallExport, $HLSInstallExport, $AdjustCabalConfigExport, $StackInstallHookExport, $StackDir)
+  Exec "$Msys2Shell" '-mingw64' '-mintty' '-c' ('{4} {6} {7} {8} [ -n ''{1}'' ] && export GHCUP_MSYS2=$(cygpath -m ''{1}'') ; [ -n ''{2}'' ] && export GHCUP_INSTALL_BASE_PREFIX=$(cygpath -m ''{2}/'') ; export PATH=$(cygpath -u ''{3}/bin''):$PATH ; export CABAL_DIR=''{5}'' ; trap ''echo Press any key to exit && read -n 1 && exit'' 2 ; [[ ''{0}'' = https* ]]  && curl --proto ''=https'' --tlsv1.2 -sSf {0} | bash || cat $(cygpath -m ''{0}'') | bash ; echo ''Press any key to exit'' && read -n 1' -f $BootstrapUrl, $MsysDir, $GhcupBasePrefix, $GhcupDir, $SilentExport, $CabalDirFull, $StackInstallExport, $HLSInstallExport, $AdjustCabalConfigExport)
 }


--- a/ghcup-0.0.6.yaml
+++ b/ghcup-0.0.6.yaml
@@ -2206,7 +2206,8 @@ ghcupDownloads:
            unknown_versioning: *stack-271-64
    2.7.3:
      viTags:
-        - old
+        - Latest
+        - Recommended
      viChangeLog: https://github.com/commercialhaskell/stack/blob/master/ChangeLog.md#v273
      viPostInstall: *stack-post
      viArch:
@@ -2231,65 +2232,4 @@ ghcupDownloads:
                RegexDir: "stack-.*"
          Linux_Alpine:
            unknown_versioning: *stack-273-64
-    2.7.3.1:
-      viTags:
-        - Latest
-        - Recommended
-      viChangeLog: https://github.com/commercialhaskell/stack/blob/master/ChangeLog.md#v273
-      viPostInstall: &stack-post-new |
-        Stack manages GHC versions internally by default. It can also use hooks to automatically
-        install and locate GHC versions utilizing GHCup:
-          https://gitlab.haskell.org/haskell/ghcup-hs#stack-hooks

-        Alternatively, you can also tell stack to use the system GHC version (whatever is in PATH):
-          stack config set system-ghc  true  --global
-
-        If you want stack to use GHCup's provided MSys2, follow the instructions here (not recommended):
-          https://gitlab.haskell.org/haskell/ghcup-hs/-/tree/stack-fork#sharing-msys2-between-stack-and-ghcup
-
-        Also check out: https://docs.haskellstack.org/en/stable/yaml_configuration
-
-        !!! GHCup ships a patched version of stack. Before reporting bugs to stack developers !!!
-        !!! make sure it is reproducible with the original stack version:                     !!!
-        !!!   https://docs.haskellstack.org/en/stable/install_and_upgrade/                    !!!
-      viArch:
-        A_64:
-          Linux_UnknownLinux:
-            unknown_versioning: &stack-2731-64
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-linux-x86_64.tar.gz
-              dlSubdir:
-                RegexDir: "stack-.*"
-              dlHash: 7c10090d568651208b6d6c003c8d78ef79099f4b472aea5ca800f3e4a7a1c6ce
-          Darwin:
-            unknown_versioning:
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-osx-x86_64.tar.gz
-              dlSubdir:
-                RegexDir: "stack-.*"
-              dlHash: 23030868be377d62ed324332d239ddd915b12f7a64c887f297e1b60a3f65894f
-          Windows:
-            unknown_versioning:
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-windows-x86_64.tar.bz2
-              dlHash: 983ac24219370cdf220f47f9edb17d0aeb831a1253fd777d322fd1bff358c511
-          Linux_Alpine:
-            unknown_versioning: *stack-2731-64
-          FreeBSD:
-            unknown_versioning:
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-freebsd-x86_64.tar.gz
-              dlHash: b6b1eb59981b8c1d3a04b061f03296b1540ecbadbc34cbd4fe712a575a155ee9
-        A_32:
-          Linux_UnknownLinux:
-            unknown_versioning: &stack-2731-32
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-linux-i386.tar.gz
-              dlHash: da2081d84517d16a8216e929582dd39caa19643c819b77c6f68f138bd177a758
-          Linux_Alpine:
-            unknown_versioning: *stack-2731-32
-        A_ARM64:
-          Linux_UnknownLinux:
-            unknown_versioning:
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-linux-aarch64.tar.gz
-              dlHash: 0e1789852a476dd87f495fa0b481309398b2bafc00cf7c8d980c91977b39d9a6
-        A_ARM:
-          Linux_UnknownLinux:
-            unknown_versioning:
-              dlUri: https://downloads.haskell.org/ghcup/unofficial-bindists/stack/2.7.3.1/stack-2.7.3.1-linux-armv7.tar.gz
-              dlHash: 13d61616c169615d80381ea0c84e13540410b736a553565cd48d10b4d2bd7f23
--- a/hooks/stack/ghc-install.sh
+++ b/hooks/stack/ghc-install.sh
@@ -1,23 +0,0 @@
-#!/bin/sh
-
-set -eu
-
-case $HOOK_GHC_TYPE in
-	bindist)
-		ghcup --offline whereis ghc $HOOK_GHC_VERSION || {
-			ghcup --cache install ghc $HOOK_GHC_VERSION && ghcup whereis ghc $HOOK_GHC_VERSION
-		}
-		;;
-	git)
-		>&2 echo "Hook doesn't support installing from source."
-		>&2 echo "Consider enabling stack GHC installs for this project, via:"
-		>&2 echo "    stack config set install-ghc true"
-		exit 1
-		;;
-	*)
-		>&2 echo "Unsupported GHC installation type: ${HOOK_GHC_TYPE}."
-		>&2 echo "Consider enabling stack GHC installs for this project, via:"
-		>&2 echo "    stack config set install-ghc true"
-		exit 2
-		;;
-esac
--- a/lib/GHCup/Download.hs
+++ b/lib/GHCup/Download.hs
@@ -320,11 +320,12 @@ download uri eDigest dest mfn etags
    -- destination dir must exist
    liftIO $ createDirRecursive' dest
    let fromFile = T.unpack . decUTF8Safe $ path
+    destFile <- liftE . reThrowAll @_ @_ @'[DownloadFailed] DownloadFailed $ getDestFile
    liftIO $ copyFile fromFile destFile
    pure destFile
  dl = do
-    let uri' = decUTF8Safe (serializeURIRef' uri)
-    lift $ $(logInfo) [i|downloading: #{uri'}|]
+    destFile <- liftE . reThrowAll @_ @_ @'[DownloadFailed] DownloadFailed $ getDestFile
+    lift $ $(logInfo) [i|downloading: #{uri'} as file #{destFile}|]

    -- destination dir must exist
    liftIO $ createDirRecursive' dest
@@ -366,7 +367,7 @@ download uri eDigest dest mfn etags
                            _ -> liftE $ throwE @_ @'[DownloadFailed] (DownloadFailed (toVariantAt @0 (MalformedHeaders headers)
                              :: V '[MalformedHeaders]))

-                          writeEtags (parseEtags headers)
+                          writeEtags destFile (parseEtags headers)
                    else
                      liftE $ lEM @_ @'[ProcessError] $ exec "curl" 
                        (o' ++ ["-fL", "-o", destFile, T.unpack uri']) Nothing Nothing
@@ -383,13 +384,13 @@ download uri eDigest dest mfn etags
                        case _exitCode of
                          ExitSuccess -> do
                            liftIO $ copyFile destFileTemp destFile
-                            writeEtags (parseEtags (decUTF8Safe' _stdErr))
+                            writeEtags destFile (parseEtags (decUTF8Safe' _stdErr))
                          ExitFailure i'
                            | i' == 8
                            , Just _ <- find (T.pack "304 Not Modified" `T.isInfixOf`) . T.lines . decUTF8Safe' $ _stdErr
                                     -> do
                                          $logDebug "Not modified, skipping download"
-                                          writeEtags (parseEtags (decUTF8Safe' _stdErr))
+                                          writeEtags destFile (parseEtags (decUTF8Safe' _stdErr))
                            | otherwise -> throwE (NonZeroExit i' "wget" opts)
                      else do
                        let opts = o' ++ ["-O", destFileTemp , T.unpack uri']
@@ -404,10 +405,10 @@ download uri eDigest dest mfn etags
                      let addHeaders = maybe mempty (\etag -> M.fromList [ (mk . E.encodeUtf8 . T.pack $ "If-None-Match"
                                                                         , E.encodeUtf8 etag)]) metag
                      liftE
-                        $ catchE @HTTPNotModified @'[DownloadFailed] @'[] (\(HTTPNotModified etag) -> lift $ writeEtags (pure $ Just etag))
+                        $ catchE @HTTPNotModified @'[DownloadFailed] @'[] (\(HTTPNotModified etag) -> lift $ writeEtags destFile (pure $ Just etag))
                        $ do
                          r <- downloadToFile https host fullPath port destFile addHeaders
-                          writeEtags (pure $ decUTF8Safe <$> getHeader r "etag")
+                          writeEtags destFile (pure $ decUTF8Safe <$> getHeader r "etag")
                    else void $ liftE $ catchE @HTTPNotModified
                                        @'[DownloadFailed]
                                   (\e@(HTTPNotModified _) ->
@@ -420,12 +421,18 @@ download uri eDigest dest mfn etags


  -- Manage to find a file we can write the body into.
-  destFile :: FilePath
-  destFile = maybe (dest </> T.unpack (decUTF8Safe (urlBaseName path)))
-                  (dest </>)
-                  mfn
+  getDestFile :: Monad m => Excepts '[NoUrlBase] m FilePath
+  getDestFile = 
+    case mfn of
+        Just fn -> pure (dest </> fn)
+        Nothing
+          | let urlBase = T.unpack (decUTF8Safe (urlBaseName path))
+          , not (null urlBase) -> pure (dest </> urlBase)
+          -- TODO: remove this once we use hpath again
+          | otherwise -> throwE $ NoUrlBase uri'

  path = view pathL' uri
+  uri' = decUTF8Safe (serializeURIRef' uri)

  parseEtags :: (MonadLogger m, MonadIO m, MonadThrow m) => T.Text -> m (Maybe T.Text)
  parseEtags stderr = do
@@ -444,8 +451,8 @@ download uri eDigest dest mfn etags
        $logDebug "No etags header found"
        pure Nothing

-  writeEtags :: (MonadLogger m, MonadIO m, MonadThrow m) => m (Maybe T.Text) -> m ()
-  writeEtags getTags = do
+  writeEtags :: (MonadLogger m, MonadIO m, MonadThrow m) => FilePath -> m (Maybe T.Text) -> m ()
+  writeEtags destFile getTags = do
    getTags >>= \case
      Just t -> do
        $logDebug [i|Writing etagsFile #{(etagsFile destFile)}|]
--- a/lib/GHCup/Errors.hs
+++ b/lib/GHCup/Errors.hs
@@ -327,6 +327,15 @@ instance Pretty UnexpectedListLength where

 instance Exception UnexpectedListLength

+data NoUrlBase = NoUrlBase Text
+  deriving Show
+
+instance Pretty NoUrlBase where
+  pPrint (NoUrlBase url) =
+    text [i|Couldn't get a base filename from url #{url}|]
+
+instance Exception NoUrlBase
+


    ------------------------