Python 2.x and 3.x support

New `depends_on :python` Dependency.
New `depends_on :python3` Dependency.

To avoid having multiple formulae with endings -py2 and -py3,
we will handle support for different pythons (2.x vs. 3.x)
in the same formula.
Further brewed vs. external python will be transparently supported.

The formula also gets a new object `python`, which is false if
no Python is available or the user has disabled it. Otherwise
it is defined and provides several support methods:

python.site_packages # the site-packages in the formula's Cellar
python.global_site_packages
python.binary # the full path to the python binary
python.prefix
python.version
python.version.major
python.version.minor
python.xy # => e.g. "python2.7"
python.incdir # includes of python
python.libdir # the python dylib library
python.pkg_config_path # used internally by brew
python.from_osx?
python.framework?
python.universal?
python.pypy?
python.standard_caveats # Text to set PYTHONPATH for python.from_osx?
python.if3then3 # => "" for 2.x and to "3" for 3.x.

Further, to avoid code duplication, `python` takes an optional
block that is run twice if the formula defines depends_on
:python AND :python3.

python do
  system python, 'setup.py', "--prefix=#{prefix}"
end

Read more in the Homebrew wiki.

1 files changed, 5 insertions, 5 deletions

diff --git a/Library/Formula/libming.rb b/Library/Formula/libming.rb
index 37ff3df92..fe32529e7 100644
--- a/Library/Formula/libming.rb
+++ b/Library/Formula/libming.rb
@@ -5,12 +5,12 @@ class Libming < Formula
   url 'http://sourceforge.net/projects/ming/files/Releases/ming-0.4.4.tar.bz2'
   sha1 'e803b3b94a00a361e3415105f26112cf6f7bac81'
 
-  option 'python', 'Build the python extension'
   option 'perl', 'Build the perl extension'
   option 'php', 'Build the php extension'
 
   depends_on :libpng
   depends_on :freetype
+  depends_on :python => :optional
   depends_on 'giflib' => :optional
 
   # Helps us find libgif.dylib, not libungif.dylib which is retired.
@@ -20,7 +20,7 @@ class Libming < Formula
 
   def install
     # TODO: Libming also includes scripting front-ends for Perl, Python, TCL
-    # and PHP.  These are disabled by default.  Figure out what it would take to
+    # and PHP. These are disabled by default. Figure out what it would take to
     # enable them.
     # - python works if we tell it to use our giflib not ungif.
     # - perl works without any change
@@ -31,9 +31,9 @@ class Libming < Formula
       --disable-silent-rules
       --prefix=#{prefix}
     ]
-    args << '--enable-python' if build.include? 'python'
-    args << '--enable-perl' if build.include? 'perl'
-    args << '--enable-php' if build.include? 'php'
+    args << '--enable-python' if build.with? 'python'
+    args << '--enable-perl' if build.with? 'perl'
+    args << '--enable-php' if build.with? 'php'
 
     system './configure', *args
     system 'make'