[commit: ghc] wip/remove-cabal-dep: Address a number of Edward's code review comments (e1d9fcd)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/remove-cabal-dep
Link       : http://ghc.haskell.org/trac/ghc/changeset/e1d9fcdef97d4787b22870f7e876e655aa28d945/ghc

>---------------------------------------------------------------

commit e1d9fcdef97d4787b22870f7e876e655aa28d945
Author: Duncan Coutts <duncan at well-typed.com>
Date:   Sun Aug 24 23:43:40 2014 +0100

    Address a number of Edward's code review comments
    
    Some others addressed as part of other recent patches.


>---------------------------------------------------------------

e1d9fcdef97d4787b22870f7e876e655aa28d945
 compiler/main/Finder.lhs                  |  1 +
 libraries/bin-package-db/GHC/PackageDb.hs |  7 +++++++
 utils/ghc-pkg/Main.hs                     | 17 +++++++++++------
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/compiler/main/Finder.lhs b/compiler/main/Finder.lhs
index 65151d9..b5ad08b 100644
--- a/compiler/main/Finder.lhs
+++ b/compiler/main/Finder.lhs
@@ -615,6 +615,7 @@ cantFindErr cannot_find _ dflags mod_name find_result
         | otherwise =
                hang (ptext (sLit "Locations searched:")) 2 $ vcat (map text files)
 
+    pkg_hidden :: PackageKey -> SDoc
     pkg_hidden pkgid =
         ptext (sLit "It is a member of the hidden package")
         <+> quotes (ppr pkgid)
diff --git a/libraries/bin-package-db/GHC/PackageDb.hs b/libraries/bin-package-db/GHC/PackageDb.hs
index eea525c..5039a01 100644
--- a/libraries/bin-package-db/GHC/PackageDb.hs
+++ b/libraries/bin-package-db/GHC/PackageDb.hs
@@ -154,6 +154,10 @@ readPackageDbForGhc file =
 
 -- | Read the part of the package DB that ghc-pkg is interested in
 --
+-- Note that the Binary instance for ghc-pkg's representation of packages
+-- is not defined in this package. This is because ghc-pkg uses Cabal types
+-- (and Binary instances for these) which this package does not depend on.
+--
 readPackageDbForGhcPkg :: Binary pkgs => FilePath -> IO pkgs
 readPackageDbForGhcPkg file =
     decodeFromFile file getDbForGhcPkg
@@ -224,6 +228,9 @@ headerMagic :: BS.ByteString
 headerMagic = BS.Char8.pack "\0ghcpkg\0"
 
 
+-- TODO: we may be able to replace the following with utils from the binary
+-- package in future.
+
 -- | Feed a 'Get' decoder with data chunks from a file.
 --
 decodeFromFile :: FilePath -> Get a -> IO a
diff --git a/utils/ghc-pkg/Main.hs b/utils/ghc-pkg/Main.hs
index ec23eb4..fdb255a 100644
--- a/utils/ghc-pkg/Main.hs
+++ b/utils/ghc-pkg/Main.hs
@@ -590,8 +590,9 @@ getPkgDatabases verbosity modify use_user use_cache expand_vars my_flags = do
             Just f  -> return (Just (f, True))
       fs -> return (Just (last fs, True))
 
-  -- If the user database exists, and for "check" and all "modify" commands
-  -- we will attempt to use the user db.
+  -- If the user database exists, and for "use_user" commands (which includes
+  -- "ghc-pkg check" and all commands that modify the db) we will attempt to
+  -- use the user db.
   let sys_databases
         | Just (user_conf,user_exists) <- mb_user_conf,
           use_user || user_exists = [user_conf, global_conf]
@@ -694,8 +695,7 @@ readParseDatabase verbosity mb_user_conf modify use_cache path
               e_tcache <- tryIO $ getModificationTime cache
               case e_tcache of
                 Left ex -> do
-                  when (   verbosity >  Normal
-                        || verbosity >= Normal && not modify) $
+                  whenReportCacheErrors $
                     if isDoesNotExistError ex
                       then do
                         warn ("WARNING: cache does not exist: " ++ cache)
@@ -727,8 +727,7 @@ readParseDatabase verbosity mb_user_conf modify use_cache path
                           pkgs <- GhcPkg.readPackageDbForGhcPkg cache
                           mkPackageDB pkgs
                       else do
-                          when (   verbosity >  Normal
-                                || verbosity >= Normal && not modify) $ do
+                          whenReportCacheErrors $ do
                               warn ("WARNING: cache is out of date: " ++ cache)
                               warn ("ghc will see an old view of this " ++
                                     "package db. Use 'ghc-pkg recache' to fix.")
@@ -741,6 +740,12 @@ readParseDatabase verbosity mb_user_conf modify use_cache path
                                        parseSingletonPackageConf verbosity f
                      pkgs <- mapM doFile $ map (path </>) confs
                      mkPackageDB pkgs
+
+                 -- We normally report cache errors for read-only commands,
+                 -- since modify commands because will usually fix the cache.
+                 whenReportCacheErrors =
+                     when (   verbosity >  Normal
+                           || verbosity >= Normal && not modify)
   where
     mkPackageDB pkgs = do
       path_abs <- absolutePath path