From d4417fba9c5db5fbbbcaac4315c52c0a6c1af652 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <p.giarrusso@gmail.com>
Date: Sat, 6 Aug 2016 13:48:28 +0200
Subject: [PATCH] Only use gtar on OpenBSD for xz archives (#2283)

Since OpenBSD's tar does not support xz, use only `gtar` there. Stick to
`tar` elsewhere.

The UX is not perfect but it's already useful.
---
 src/Stack/Setup.hs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
index d70b7d58be..76555d2188 100644
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -819,10 +819,16 @@ installGHCPosix version _ archiveFile archiveType destDir = do
             TarBz2 -> return "bzip2"
             TarGz -> return "gzip"
             SevenZ -> error "Don't know how to deal with .7z files on non-Windows"
+    -- Slight hack: OpenBSD's tar doesn't support xz.
+    -- https://github.com/commercialhaskell/stack/issues/2283#issuecomment-237980986
+    let tarDep =
+          case (platform, archiveType) of
+            (Platform _ Cabal.OpenBSD, TarXz) -> checkDependency "gtar"
+            _ -> checkDependency "tar"
     (zipTool, makeTool, tarTool) <- checkDependencies $ (,,)
         <$> checkDependency zipTool'
         <*> (checkDependency "gmake" <|> checkDependency "make")
-        <*> checkDependency "tar"
+        <*> tarDep
 
     $logDebug $ "ziptool: " <> T.pack zipTool
     $logDebug $ "make: " <> T.pack makeTool