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, 7 insertions, 1 deletions

diff --git a/Library/Formula/vim.rb b/Library/Formula/vim.rb
index d3f5ff2bf..f48ef60a1 100644
--- a/Library/Formula/vim.rb
+++ b/Library/Formula/vim.rb
@@ -7,7 +7,10 @@ class Vim < Formula
   sha1 'f308d219dd9c6b56e84109ace4e7487a101088f5'
   head 'https://vim.googlecode.com/hg/'
 
-  env :std # To find interpreters
+  # We only have special support for finding depends_on :python, but not yet for
+  # :ruby, :perl etc., so we use the standard environment that leaves the
+  # PATH as the user has set it right now.
+  env :std
 
   depends_on :hg => :build if build.head?
 
@@ -20,6 +23,9 @@ class Vim < Formula
     option "without-#{language}", "Build vim without #{language} support"
   end
 
+  depends_on :python unless build.without? 'python'
+  depends_on :python3 if build.with? 'python3'
+
   option "disable-nls", "Build vim without National Language Support (translated messages, keymaps)"
 
   def install