From efbbd977b60efc357b134124c8a9152d9b704811 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Thu, 14 Jul 2005 15:12:20 +0000
Subject: [PATCH] [project @ 2005-07-14 15:12:20 by simonmar] - -package P
 hides all other versions of P (this was advertised     in
 the documentation, but wasn't actually implemented in 6.4)

  - if multiple packages with the same name are still exposed after
    the flags have been processed, then all except the latest version
    are hidden.
---
 ghc/compiler/main/Packages.lhs |   35 ++++++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/ghc/compiler/main/Packages.lhs b/ghc/compiler/main/Packages.lhs
index 137b3c0..6f0b867 100644
--- a/ghc/compiler/main/Packages.lhs
+++ b/ghc/compiler/main/Packages.lhs
@@ -291,9 +291,11 @@ mkPackageState dflags orig_pkg_db = do
 	procflags pkgs expl (ExposePackage str : flags) = do
 	   case partition (matches str) pkgs of
 		([],_)   -> missingPackageErr str
-		([p],ps) -> procflags (p':ps) (addOneToUniqSet expl pkgid) flags
+		([p],ps) -> procflags (p':ps') expl' flags
 		  where pkgid = packageConfigId p
 			p' = p {exposed=True}
+		        ps' = hideAll (pkgName (package p)) ps
+			expl' = addOneToUniqSet expl pkgid
 		(ps,_)   -> multiplePackagesErr str ps
 	procflags pkgs expl (HidePackage str : flags) = do
 	   case partition (matches str) pkgs of
@@ -313,9 +315,35 @@ mkPackageState dflags orig_pkg_db = do
 	matches str p
 		=  str == showPackageId (package p)
 		|| str == pkgName (package p)
+
+	-- When a package is requested to be exposed, we hide all other
+	-- packages with the same name.
+	hideAll name ps = map maybe_hide ps
+	  where maybe_hide p | pkgName (package p) == name = p {exposed=False}
+			     | otherwise                   = p
   --
   (pkgs1,explicit) <- procflags (eltsUFM orig_pkg_db) emptyUniqSet flags
   --
+  -- hide all packages for which there is also a later version
+  -- that is already exposed.  This just makes it non-fatal to have two
+  -- versions of a package exposed, which can happen if you install a
+  -- later version of a package in the user database, for example.
+  --
+  let
+	pkgs2 = map maybe_hide pkgs1
+	   where maybe_hide p
+		   | a_later_version_is_exposed = p {exposed=False}
+		   | otherwise                  = p
+		  where myname = pkgName (package p)
+			myversion = pkgVersion (package p)
+			a_later_version_is_exposed
+			  = not (null [ p | p <- pkgs1, let pkg = package p,
+					    pkgName pkg == myname,
+					    pkgVersion pkg > myversion ])
+  --
+  -- Eliminate any packages which have dangling dependencies (perhaps
+  -- because the package was removed by -ignore-package).
+  --
   let
 	elimDanglingDeps pkgs = 
 	   case partition (hasDanglingDeps pkgs) pkgs of
@@ -326,10 +354,7 @@ mkPackageState dflags orig_pkg_db = do
 	  where dangling pid = pid `notElem` all_pids
 		all_pids = map package pkgs
   --
-  -- Eliminate any packages which have dangling dependencies (perhaps
-  -- because the package was removed by -ignore-package).
-  --
-  let pkgs = elimDanglingDeps pkgs1
+  let pkgs = elimDanglingDeps pkgs2
       pkg_db = extendPackageConfigMap emptyPackageConfigMap pkgs
   --
   -- Find the transitive closure of dependencies of exposed
-- 
1.7.10.4