Use BSD tar's libarchive LZMA support if available

Avoid using an unnecessary `xz` dependency when it's not needed.

7 files changed, 59 insertions, 21 deletions

diff --git a/Library/Homebrew/dependency_collector.rb b/Library/Homebrew/dependency_collector.rb
index 02c781998..814084255 100644
--- a/Library/Homebrew/dependency_collector.rb
+++ b/Library/Homebrew/dependency_collector.rb
@@ -61,6 +61,10 @@ class DependencyCollector
     parse_spec(spec, Array(tags))
   end
 
+  def self.tar_needs_xz_dependency?
+    !new.xz_dep([]).nil?
+  end
+
   private
 
   def parse_spec(spec, tags)
@@ -113,7 +117,7 @@ class DependencyCollector
     when :osxfuse    then OsxfuseRequirement.new(tags)
     when :perl       then PerlRequirement.new(tags)
     when :tuntap     then TuntapRequirement.new(tags)
-    when :ant        then ant_dep(spec, tags)
+    when :ant        then ant_dep(tags)
     when :emacs      then EmacsRequirement.new(tags)
     # Tiger's ld is too old to properly link some software
     when :ld64       then LD64Dependency.new if MacOS.version < :leopard
@@ -134,8 +138,12 @@ class DependencyCollector
     spec.new(tags)
   end
 
-  def ant_dep(spec, tags)
-    Dependency.new(spec.to_s, tags)
+  def ant_dep(tags)
+    Dependency.new("ant", tags)
+  end
+
+  def xz_dep(tags)
+    Dependency.new("xz", tags)
   end
 
   def resource_dep(spec, tags)
@@ -164,7 +172,7 @@ class DependencyCollector
 
   def parse_url_spec(url, tags)
     case File.extname(url)
-    when ".xz"          then Dependency.new("xz", tags)
+    when ".xz"          then xz_dep(tags)
     when ".lha", ".lzh" then Dependency.new("lha", tags)
     when ".lz"          then Dependency.new("lzip", tags)
     when ".rar"         then Dependency.new("unrar", tags)
diff --git a/Library/Homebrew/development_tools.rb b/Library/Homebrew/development_tools.rb
index 7221e5b52..3e1f16d2a 100644
--- a/Library/Homebrew/development_tools.rb
+++ b/Library/Homebrew/development_tools.rb
@@ -88,6 +88,10 @@ class DevelopmentTools
       @clang_version = @clang_build_version = nil
       @non_apple_gcc_version = {}
     end
+
+    def tar_supports_xz?
+      false
+    end
   end
 end
 
diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index 4f2f1b6b0..057768246 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -222,7 +222,7 @@ end
 
 class AbstractFileDownloadStrategy < AbstractDownloadStrategy
   def stage
-    case cached_location.compression_type
+    case type = cached_location.compression_type
     when :zip
       with_system_path { quiet_safe_system "unzip", "-qq", cached_location }
       chdir
@@ -230,19 +230,23 @@ class AbstractFileDownloadStrategy < AbstractDownloadStrategy
       with_system_path { buffered_write("gunzip") }
     when :bzip2_only
       with_system_path { buffered_write("bunzip2") }
-    when :gzip, :bzip2, :compress, :tar
+    when :gzip, :bzip2, :xz, :compress, :tar
       tar_flags = "x"
-      # Older versions of tar require an explicit format flag
-      if cached_location.compression_type == :gzip
+      if type == :gzip
         tar_flags << "z"
-      elsif cached_location.compression_type == :bzip2
+      elsif type == :bzip2
         tar_flags << "j"
+      elsif type == :xz
+        tar_flags << "J"
       end
       tar_flags << "f"
-      with_system_path { safe_system "tar", tar_flags, cached_location }
-      chdir
-    when :xz
-      with_system_path { pipe_to_tar(xzpath) }
+      with_system_path do
+        if type == :xz && DependencyCollector.tar_needs_xz_dependency?
+          pipe_to_tar(xzpath)
+        else
+          safe_system "tar", tar_flags, cached_location
+        end
+      end
       chdir
     when :lzip
       with_system_path { pipe_to_tar(lzippath) }
diff --git a/Library/Homebrew/extend/os/mac/dependency_collector.rb b/Library/Homebrew/extend/os/mac/dependency_collector.rb
index ee98045b6..72c619105 100644
--- a/Library/Homebrew/extend/os/mac/dependency_collector.rb
+++ b/Library/Homebrew/extend/os/mac/dependency_collector.rb
@@ -1,6 +1,11 @@
 class DependencyCollector
-  def ant_dep(spec, tags)
+  def ant_dep(tags)
     return if MacOS.version < :mavericks
-    Dependency.new(spec.to_s, tags)
+    Dependency.new("ant", tags)
+  end
+
+  def xz_dep(tags)
+    return if MacOS.version >= :lion
+    Dependency.new("xz", tags)
   end
 end
diff --git a/Library/Homebrew/extend/os/mac/development_tools.rb b/Library/Homebrew/extend/os/mac/development_tools.rb
index 381b26e66..7c97b9d69 100644
--- a/Library/Homebrew/extend/os/mac/development_tools.rb
+++ b/Library/Homebrew/extend/os/mac/development_tools.rb
@@ -76,5 +76,9 @@ class DevelopmentTools
         end
       end
     end
+
+    def tar_supports_xz?
+      false
+    end
   end
 end
diff --git a/Library/Homebrew/test/test_dependency_collector.rb b/Library/Homebrew/test/test_dependency_collector.rb
index 4e87c8515..1c7f70118 100644
--- a/Library/Homebrew/test/test_dependency_collector.rb
+++ b/Library/Homebrew/test/test_dependency_collector.rb
@@ -114,12 +114,6 @@ class DependencyCollectorTests < Homebrew::TestCase
     assert_nil @d.add(resource)
   end
 
-  def test_resource_dep_xz_url
-    resource = Resource.new
-    resource.url("http://example.com/foo.tar.xz")
-    assert_equal Dependency.new("xz", [:build]), @d.add(resource)
-  end
-
   def test_resource_dep_lz_url
     resource = Resource.new
     resource.url("http://example.com/foo.lz")
diff --git a/Library/Homebrew/test/test_os_mac_dependency_collector.rb b/Library/Homebrew/test/test_os_mac_dependency_collector.rb
index 05b466c94..d3a45b1fb 100644
--- a/Library/Homebrew/test/test_os_mac_dependency_collector.rb
+++ b/Library/Homebrew/test/test_os_mac_dependency_collector.rb
@@ -14,6 +14,11 @@ class OSMacDependencyCollectorTests < Homebrew::TestCase
     DependencyCollector.clear_cache
   end
 
+  def test_tar_needs_xz_dependency
+    MacOS.stubs(:version).returns(MacOS::Version.new("10.7"))
+    refute DependencyCollector.tar_needs_xz_dependency?
+  end
+
   def test_ld64_dep_pre_leopard
     MacOS.stubs(:version).returns(MacOS::Version.new("10.4"))
     assert_equal LD64Dependency.new, @d.build(:ld64)
@@ -35,4 +40,18 @@ class OSMacDependencyCollectorTests < Homebrew::TestCase
     @d.add ant: :build
     assert_nil find_dependency("ant")
   end
+
+  def test_resource_dep_xz_url_pre_lion
+    MacOS.stubs(:version).returns(MacOS::Version.new("10.6"))
+    resource = Resource.new
+    resource.url("http://example.com/foo.tar.xz")
+    assert_equal Dependency.new("xz", [:build]), @d.add(resource)
+  end
+
+  def test_resource_dep_xz_lion_or_newer
+    MacOS.stubs(:version).returns(MacOS::Version.new("10.7"))
+    resource = Resource.new
+    resource.url("http://example.com/foo.tar.xz")
+    assert_nil @d.add(resource)
+  end
 end