directory: ensure xdg compliance (Fix #6077)

compiler/GHC/Driver/Session.hs

@@ -867,7 +867,7 @@ opt_i dflags= toolSettings_opt_i $ toolSettings dflags
 versionedAppDir :: String -> ArchOS -> MaybeT IO FilePath
 versionedAppDir appname platform = do
   -- Make sure we handle the case the HOME isn't set (see #11678)
-  appdir <- tryMaybeT $ getAppUserDataDirectory appname
+  appdir <- tryMaybeT $ getXdgDirectory XdgData appname
   return $ appdir </> versionedFilePath platform
 
 versionedFilePath :: ArchOS -> FilePath

docs/users_guide/9.2.1-notes.rst

@@ -101,6 +101,10 @@ GHCi
   :envvar:`EDITOR`, following UNIX convention.
   (:ghc-ticket:`19030`)
 
+- GHC now follows by default the XDG Base Directory Specification. If
+  ``$HOME/.ghc`` is found it will fallback to the old paths to give you
+  time to migrate. This fallback will be removed in three releases.
+
 Runtime system
 ~~~~~~~~~~~~~~
 

docs/users_guide/ghci.rst

@@ -2063,7 +2063,7 @@ mostly obvious.
     :reverse: -fno-local-ghci-history
     :category:
 
-    By default, GHCi keeps global history in ``~/.ghc/ghci_history`` or
+    By default, GHCi keeps global history in ``$XDG_DATA_HOME/ghc/ghci_history`` or
     ``%APPDATA%/<app>/ghci_history``, but you can use current directory, e.g.:
 
     .. code-block:: none
@@ -3248,7 +3248,7 @@ they exist:
    Unix or :file:`C:/Documents and Settings/user/Application
    Data/ghc` on Windows.
 
-2. :file:`$HOME/.ghci`
+2. :file:`$XDG_CONFIG_HOME/.ghci`
 
 3. :file:`./.ghci`
 

docs/users_guide/packages.rst

@@ -393,7 +393,7 @@ GHC knows about two package databases in particular:
    e.g. ``/usr/lib/ghc-6.12.1/package.conf.d``.
 
 -  The *user package database* private to each user. On Unix systems this will
-   be ``$HOME/.ghc/arch-os-version/package.conf.d``, and on Windows it will
+   be ``$XDG_DATA_HOME/ghc/arch-os-version/package.conf.d``, and on Windows it will
    be something like
    ``C:\Documents And Settings\user\ghc\package.conf.d``. The
    ``ghc-pkg`` tool knows where this file should be located, and will
@@ -515,7 +515,7 @@ The ``GHC_PACKAGE_PATH`` environment variable
 
     .. code-block:: none
 
-        $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
+        $ export GHC_PACKAGE_PATH=$XDG_DATA_HOME/.my-ghc-packages.conf:
 
     To check whether your `GHC_PACKAGE_PATH` setting is doing the right
     thing, ``ghc-pkg list`` will list all the databases in use, in the
@@ -578,7 +578,7 @@ must be relative to the location of the package environment file.
     :category:
 
     Use the package environment in ⟨file⟩, or in
-    ``$HOME/.ghc/arch-os-version/environments/⟨name⟩``
+    ``$XDG_DATA_HOME/ghc/arch-os-version/environments/⟨name⟩``
     If set to ``-`` no package environment is read.
 
 .. envvar:: GHC_ENVIRONMENT
@@ -591,13 +591,13 @@ locations:
 
 -  File ⟨file⟩ if you pass the option :ghc-flag:`-package-env ⟨file⟩|⟨name⟩`.
 
--  File ``$HOME/.ghc/arch-os-version/environments/name`` if you pass the
+-  File ``$XDG_DATA_HOME/ghc/arch-os-version/environments/name`` if you pass the
    option ``-package-env ⟨name⟩``.
 
 -  File ⟨file⟩ if the environment variable :envvar:`GHC_ENVIRONMENT` is set to
    ⟨file⟩.
 
--  File ``$HOME/.ghc/arch-os-version/environments/name`` if the
+-  File ``$XDG_DATA_HOME/ghc/arch-os-version/environments/name`` if the
    environment variable :envvar:`GHC_ENVIRONMENT` is set to ⟨name⟩.
 
 Additionally, unless ``-hide-all-packages`` is specified ``ghc`` will also
@@ -606,7 +606,7 @@ look for the package environment in the following locations:
 -  File ``.ghc.environment.arch-os-version`` if it exists in the current
    directory or any parent directory (but not the user's home directory).
 
--  File ``$HOME/.ghc/arch-os-version/environments/default`` if it
+-  File ``$XDG_DATA_HOME/ghc/arch-os-version/environments/default`` if it
    exists.
 
 Package environments can be modified by further command line arguments;

ghc/GHCi/UI.hs

@@ -587,7 +587,21 @@ ghciLogAction lastErrLocations old_log_action
 
 withGhcAppData :: (FilePath -> IO a) -> IO a -> IO a
 withGhcAppData right left = do
-    either_dir <- tryIO (getAppUserDataDirectory "ghc")
+    either_dir <- tryIO (getXdgDirectory XdgData "ghc")
+    case either_dir of
+        Right dir ->
+            do createDirectoryIfMissing False dir `catchIO` \_ -> return ()
+               right dir
+        _ -> left
+
+withGhcConfig :: (FilePath -> IO a) -> IO a -> IO a
+withGhcConfig right left = do
+    old_path <- getAppUserDataDirectory "ghc"
+    use_old_path <- doesPathExist old_path
+    let path = (if use_old_path
+                 then getAppUserDataDirectory "ghc"
+                 else getXdgDirectory XdgConfig "ghc")
+    either_dir <- tryIO (path)
     case either_dir of
         Right dir ->
             do createDirectoryIfMissing False dir `catchIO` \_ -> return ()
@@ -600,7 +614,7 @@ runGHCi paths maybe_exprs = do
   let
    ignore_dot_ghci = gopt Opt_IgnoreDotGhci dflags
 
-   app_user_dir = liftIO $ withGhcAppData
+   app_user_dir = liftIO $ withGhcConfig
                     (\dir -> return (Just (dir </> "ghci.conf")))
                     (return Nothing)
 

utils/ghc-pkg/Main.hs

@@ -58,8 +58,8 @@ import Distribution.Simple.Utils (toUTF8BS, writeUTF8File, readUTF8File)
 import qualified Data.Version as Version
 import System.FilePath as FilePath
 import qualified System.FilePath.Posix as FilePath.Posix
-import System.Directory ( getAppUserDataDirectory, createDirectoryIfMissing,
-                          getModificationTime )
+import System.Directory ( getXdgDirectory, createDirectoryIfMissing,
+                          getModificationTime, XdgDirectory ( XdgData ) )
 import Text.Printf
 
 import Prelude
@@ -634,8 +634,8 @@ getPkgDatabases verbosity mode use_user use_cache expand_vars my_flags = do
   let no_user_db = FlagNoUserDb `elem` my_flags
 
   -- get the location of the user package database, and create it if necessary
-  -- getAppUserDataDirectory can fail (e.g. if $HOME isn't set)
-  e_appdir <- tryIO $ getAppUserDataDirectory "ghc"
+  -- getXdgDirectory can fail (e.g. if $HOME isn't set)
+  e_appdir <- tryIO $ getXdgDirectory XdgData "ghc"
 
   mb_user_conf <-
     case [ f | FlagUserConfig f <- my_flags ] of