Add support for nested archives.

Library/Homebrew/test/unpack_strategy_spec.rb

@@ -15,6 +15,29 @@ RSpec.shared_examples "#extract" do |children: []|
   end
 end
 
+describe UnpackStrategy do
+  describe "#extract_nestedly" do
+    let(:file_name) { "file" }
+    let(:nested_archive) {
+      dir = mktmpdir
+
+      (dir/"file").write "This file was inside a GZIP inside a BZIP2."
+      system "gzip", dir.children.first
+      system "bzip2", dir.children.first
+
+      dir.children.first
+    }
+    let(:unpack_dir) { mktmpdir }
+    subject(:strategy) { described_class.detect(nested_archive) }
+
+    it "can extract nested archives" do
+      strategy.extract_nestedly(to: unpack_dir)
+
+      expect(File.read(unpack_dir/file_name)).to eq("This file was inside a GZIP inside a BZIP2.")
+    end
+  end
+end
+
 describe UncompressedUnpackStrategy do
   let(:path) {
     (mktmpdir/"test").tap do |path|

Library/Homebrew/unpack_strategy.rb

@@ -67,6 +67,30 @@ class UnpackStrategy
     unpack_dir.mkpath
     extract_to_dir(unpack_dir, basename: basename)
   end
+
+  def extract_nestedly(to: nil, basename: nil)
+    if is_a?(UncompressedUnpackStrategy)
+      extract(to: to, basename: basename)
+      return
+    end
+
+    Dir.mktmpdir do |tmp_unpack_dir|
+      tmp_unpack_dir = Pathname(tmp_unpack_dir)
+
+      extract(to: tmp_unpack_dir, basename: basename)
+
+      children = tmp_unpack_dir.children
+
+      if children.count == 1
+        s = self.class.detect(children.first)
+
+        s.extract_nestedly(to: to, basename: basename)
+        next
+      end
+
+      DirectoryUnpackStrategy.new(tmp_unpack_dir).extract(to: to)
+    end
+  end
 end
 
 class DirectoryUnpackStrategy < UnpackStrategy
@@ -166,7 +190,7 @@ class CompressUnpackStrategy < TarUnpackStrategy
   end
 end
 
-class XzUnpackStrategy < UncompressedUnpackStrategy
+class XzUnpackStrategy < UnpackStrategy
   def self.can_extract?(path:, magic_number:)
     magic_number.match?(/\A\xFD7zXZ\x00/n)
   end
@@ -192,7 +216,7 @@ class XzUnpackStrategy < UncompressedUnpackStrategy
   end
 end
 
-class Bzip2UnpackStrategy < UncompressedUnpackStrategy
+class Bzip2UnpackStrategy < UnpackStrategy
   def self.can_extract?(path:, magic_number:)
     magic_number.match?(/\ABZh/n)
   end
@@ -200,12 +224,12 @@ class Bzip2UnpackStrategy < UncompressedUnpackStrategy
   private
 
   def extract_to_dir(unpack_dir, basename:)
-    super
+    FileUtils.cp path, unpack_dir/basename, preserve: true
     safe_system "bunzip2", "-q", unpack_dir/basename
   end
 end
 
-class GzipUnpackStrategy < UncompressedUnpackStrategy
+class GzipUnpackStrategy < UnpackStrategy
   def self.can_extract?(path:, magic_number:)
     magic_number.match?(/\A\037\213/n)
   end
@@ -213,12 +237,12 @@ class GzipUnpackStrategy < UncompressedUnpackStrategy
   private
 
   def extract_to_dir(unpack_dir, basename:)
-    super
+    FileUtils.cp path, unpack_dir/basename, preserve: true
     safe_system "gunzip", "-q", "-N", unpack_dir/basename
   end
 end
 
-class LzipUnpackStrategy < UncompressedUnpackStrategy
+class LzipUnpackStrategy < UnpackStrategy
   def self.can_extract?(path:, magic_number:)
     magic_number.match?(/\ALZIP/n)
   end
@@ -226,7 +250,7 @@ class LzipUnpackStrategy < UncompressedUnpackStrategy
   private
 
   def extract_to_dir(unpack_dir, basename:)
-    super
+    FileUtils.cp path, unpack_dir/basename, preserve: true
     safe_system Formula["lzip"].opt_bin/"lzip", "-d", "-q", unpack_dir/basename
   end
 end