From b5c693fa5882f5219580929b045bf5d8a1a5ef61 Mon Sep 17 00:00:00 2001
From: Tamar Christina <tamar@zhox.com>
Date: Tue, 26 Dec 2017 07:36:54 +0000
Subject: [PATCH] Cabal: Fix path redundancy new-build output folders.

---
 Cabal/Distribution/Simple/InstallDirs.hs             |  4 ++--
 cabal-install/Distribution/Client/ProjectBuilding.hs | 10 ++++------
 cabal-install/Distribution/Client/Store.hs           |  5 ++++-
 cabal-install/changelog                              |  2 ++
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/Cabal/Distribution/Simple/InstallDirs.hs b/Cabal/Distribution/Simple/InstallDirs.hs
index f74bc14d6cd..96c178abb04 100644
--- a/Cabal/Distribution/Simple/InstallDirs.hs
+++ b/Cabal/Distribution/Simple/InstallDirs.hs
@@ -59,7 +59,7 @@ import Distribution.Text
 import System.Directory (getAppUserDataDirectory)
 import System.FilePath
   ( (</>), isPathSeparator
-  , pathSeparator, dropDrive )
+  , pathSeparator, takeBaseName )
 
 #ifdef mingw32_HOST_OS
 import qualified Prelude
@@ -286,7 +286,7 @@ absoluteInstallDirs :: PackageIdentifier
                     -> InstallDirs FilePath
 absoluteInstallDirs pkgId libname compilerId copydest platform dirs =
     (case copydest of
-       CopyTo destdir -> fmap ((destdir </>) . dropDrive)
+       CopyTo destdir -> fmap ((destdir </>) . takeBaseName)
        _              -> id)
   . appendSubdirs (</>)
   . fmap fromPathTemplate
diff --git a/cabal-install/Distribution/Client/ProjectBuilding.hs b/cabal-install/Distribution/Client/ProjectBuilding.hs
index 1e91b5e187c..3e88b823d43 100644
--- a/cabal-install/Distribution/Client/ProjectBuilding.hs
+++ b/cabal-install/Distribution/Client/ProjectBuilding.hs
@@ -940,12 +940,10 @@ buildAndInstallUnpackedPackage verbosity
     annotateFailure mlogFile InstallFailed $ do
 
       let copyPkgFiles tmpDir = do
-            setup Cabal.copyCommand (copyFlags tmpDir)
-            -- Note that the copy command has put the files into
-            -- @$tmpDir/$prefix@ so we need to return this dir so
-            -- the store knows which dir will be the final store entry.
-            let prefix   = dropDrive (InstallDirs.prefix (elabInstallDirs pkg))
+            let prefix   = let path = InstallDirs.prefix (elabInstallDirs pkg)
+                           in takeBaseName path
                 entryDir = tmpDir </> prefix
+            setup Cabal.copyCommand (copyFlags entryDir)
             LBS.writeFile
               (entryDir </> "cabal-hash.txt")
               (renderPackageHashInputs (packageHashInputs pkgshared pkg))
@@ -954,7 +952,7 @@ buildAndInstallUnpackedPackage verbosity
             -- While this breaks the prefix-relocatable property of the lirbaries
             -- it is necessary on macOS to stay under the load command limit of the
             -- macOS mach-o linker. See also @PackageHash.hashedInstalledPackageIdVeryShort@.
-            otherFiles <- filter (not . isPrefixOf entryDir) <$> listFilesRecursive tmpDir 
+            otherFiles <- filter (not . isPrefixOf entryDir) <$> listFilesRecursive tmpDir
             -- here's where we could keep track of the installed files ourselves
             -- if we wanted to by making a manifest of the files in the tmp dir
             return (entryDir, otherFiles)
diff --git a/cabal-install/Distribution/Client/Store.hs b/cabal-install/Distribution/Client/Store.hs
index 4afdb3a264f..2649eb1dcd2 100644
--- a/cabal-install/Distribution/Client/Store.hs
+++ b/cabal-install/Distribution/Client/Store.hs
@@ -209,7 +209,10 @@ newStoreEntry verbosity storeDirLayout@StoreDirLayout{..}
             -- Atomically rename the temp dir to the final store entry location.
             renameDirectory incomingEntryDir finalEntryDir
             forM_ otherFiles $ \file -> do
-              let finalStoreFile = storeDirectory compid </> makeRelative (incomingTmpDir </> (dropDrive (storeDirectory compid))) file
+              let finalStoreFile = storeDirectory compid
+                                </> makeRelative (incomingTmpDir
+                                     </> (takeBaseName (storeDirectory compid)))
+                                     file
               createDirectoryIfMissing True (takeDirectory finalStoreFile)
               renameFile file finalStoreFile
 
diff --git a/cabal-install/changelog b/cabal-install/changelog
index 9ed760eb5ac..861e19fc5e9 100644
--- a/cabal-install/changelog
+++ b/cabal-install/changelog
@@ -46,6 +46,8 @@
 	* Added support for '--enable-tests' and '--enable-benchmarks' to
 	'cabal fetch' (#4948).
 	* Removed support for building cabal-install with GHC < 7.10.
+	* Redundancy in new-build incoming store paths removed. This makes incoming
+	tmp paths much shorter. (#4515, #3972)
 
 2.0.0.1 Mikhail Glushenkov <mikhail.glushenkov@gmail.com> December 2017
 	* Support for GHC's numeric -g debug levels (#4673).