From ec7e22e16fbaa09ca01b8e2fff84ba5c7613b5b0 Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Mon, 9 Jul 2018 21:20:00 +0200
Subject: [PATCH] Fix `XzUnpackStrategy`.

---
 Library/Homebrew/unpack_strategy.rb | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/Library/Homebrew/unpack_strategy.rb b/Library/Homebrew/unpack_strategy.rb
index a23406805f..ff41938fc0 100644
--- a/Library/Homebrew/unpack_strategy.rb
+++ b/Library/Homebrew/unpack_strategy.rb
@@ -151,7 +151,7 @@ class CompressUnpackStrategy < TarUnpackStrategy
   end
 end
 
-class XzUnpackStrategy < TarUnpackStrategy
+class XzUnpackStrategy < UnpackStrategy
   def self.can_extract?(path:, magic_number:)
     magic_number.match?(/\A\xFD7zXZ\x00/n)
   end
@@ -159,13 +159,23 @@ class XzUnpackStrategy < TarUnpackStrategy
   private
 
   def extract_to_dir(unpack_dir, basename:)
-    if DependencyCollector.tar_needs_xz_dependency?
-      unpack_path = unpack_dir/path.basename
-      FileUtils.cp path, unpack_path, preserve: true
+    unpack_path = unpack_dir/path.basename
+    FileUtils.cp path, unpack_path, preserve: true
 
-      safe_system Formula["xz"].opt_bin/"xz", "-d", "-q", "-T0", unpack_path
-    else
-      super
+    safe_system Formula["xz"].opt_bin/"xz", "-d", "-q", "-T0", unpack_path
+
+    extract_nested_tar(unpack_dir, basename: basename)
+  end
+
+  def extract_nested_tar(unpack_dir, basename:)
+    return unless DependencyCollector.tar_needs_xz_dependency?
+    return if (children = unpack_dir.children).count != 1
+    return if (tar = children.first).extname != ".tar"
+
+    Dir.mktmpdir do |tmpdir|
+      tmpdir = Pathname(tmpdir)
+      FileUtils.mv tar, tmpdir/tar.basename
+      TarUnpackStrategy.new(tmpdir/tar.basename).extract(to: unpack_dir, basename: basename)
     end
   end
 end