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, 296 insertions, 0 deletions

diff --git a/Library/Homebrew/requirements/python_dependency.rb b/Library/Homebrew/requirements/python_dependency.rb
new file mode 100644
index 000000000..194d434c7
--- /dev/null
+++ b/Library/Homebrew/requirements/python_dependency.rb
@@ -0,0 +1,296 @@
+require 'requirement'
+
+# We support Python 2.x and 3.x, either brewed or external.
+# This requirement locates the correct CPython binary (no PyPy), provides
+# support methods like `site_packages`, and writes our sitecustomize.py file.
+# In `dependency_collector.rb`, special `:python` and `:python3` shortcuts are
+# defined. You can specify a minimum version of the Python that needs to be
+# present, but since not every package is ported to 3.x yet,
+# `PythonInstalled("2")` is not satisfied by 3.x.
+# In a formula that shall provide support for 2.x and 3.x, the idiom is:
+# depends_on :python
+# depends_on :python3 => :optional # or :recommended
+#
+# Todo:
+# - Allow further options that choose: universal, framework?, brewed?...
+class PythonInstalled < Requirement
+  attr_reader :min_version
+  attr_reader :if3then3
+  attr_reader :site_packages
+  attr_accessor :site_packages
+
+  fatal true  # you can still make Python optional by `depends_on :python => :optional`
+
+  class PythonVersion < Version
+    def major
+      to_a[0].to_s.to_i  # Python's major.minor are always ints.
+    end
+    def minor
+      to_a[1].to_s.to_i
+    end
+  end
+
+  def initialize(*tags)
+    # Extract the min_version if given. Default to python 2.X else
+    tags.flatten!
+    if /(\d+\.)*\d+/ === tags.first
+      @min_version = PythonVersion.new(tags.shift)
+    else
+      @min_version = PythonVersion.new("2.7")  # default
+    end
+
+    # often used idiom: e.g. sipdir = "share/sip" + python.if3then3
+    if @min_version.major == 3
+      @if3then3 = "3"
+    else
+      @if3then3 = ""
+    end
+
+    # Set name according to the major version.
+    # The name is used to generate the options like --without-python3
+    @name = "python" + @if3then3
+
+    # will be set later by the python_helper, because it needs the
+    # formula prefix to set site_packages
+    @site_packages = nil
+
+    super tags
+  end
+
+  # Note that during `satisfy` we still have the PATH as the user has set.
+  # We look for a brewed python or an external Python and store the loc of
+  # that binary for later usage. (See Formula#python)
+  satisfy :build_env => false do
+    @unsatisfied_because = "This formula needs #{@name}.\n"
+    if binary.nil?
+      @unsatisfied_because += "But no `#{@name}` found in your PATH! Consider to `brew install #{@name}`."
+      false
+    elsif pypy?
+      @unsatisfied_because += "Your #{@name} executable appears to be a PyPy, which is not supported."
+      false
+    elsif version.major != @min_version.major
+      @unsatisfied_because += "No Python #{@min_version.major}.x found!"
+      false
+    elsif version < @min_version
+      @unsatisfied_because += "Python version #{version} is too old (need at least #{@min_version})."
+      false
+    elsif @min_version.major == 2 && `python -c "import sys; print(sys.version_info.major)"`.strip == "3"
+      @unsatisfied_because += "Your `python` points to a Python 3.x. This is not supported."
+      false
+    else
+      true
+    end
+  end
+
+  # The full path to the python or python3 executable, depending on `version`.
+  def binary
+    if brewed?
+      # If the python is brewed we always prefer it!
+      # Note, we don't support homebrew/versions/pythonXX.rb, though.
+      Formula.factory(@name).opt_prefix/"bin/python#{@min_version.major}"
+    else
+      p = which(@name)
+      raise "PythonInstalled: #{p} is not executable" if !p.nil? && !p.executable?
+      p
+    end
+  end
+
+  # The python prefix (special cased for a brewed python to point into the opt_prefix)
+  def prefix
+    if brewed?
+      # Homebrew since a long while only supports frameworked python
+      HOMEBREW_PREFIX/"opt/#{name}/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}"
+    elsif from_osx?
+      # Python on OS X has been stripped off its includes (unless you install the CLT), therefore we use the MacOS.sdk.
+      Pathname.new("#{MacOS.sdk_path}/System/Library/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}")
+    else
+      # What Python knows about itself
+      Pathname.new(`#{binary} -c 'import sys;print(sys.prefix)'`.strip)
+    end
+  end
+
+  # Get the actual x.y.z version by asking python (or python3 if @min_version>=3)
+  def version
+    @version ||= PythonVersion.new(`#{binary} -c 'import sys;print(sys.version[:5])'`.strip)
+  end
+
+  # python.xy => "python2.7" is often used (and many formulae had this as `which_python`).
+  def xy
+    "python#{version.major}.#{version.minor}"
+  end
+
+  # Homebrew's global site-packages. The local ones are populated by the
+  # python_helper method when the `prefix` of a formula is known.
+  def global_site_packages
+    HOMEBREW_PREFIX/"lib/#{xy}/site-packages"
+  end
+
+  # Dir containing Python.h and others.
+  def incdir
+    if (from_osx? || brewed?) && framework?
+      prefix/"Headers"
+    else
+      # For all other we use Python's own standard method (works with a non-framework version, too)
+      Pathname.new(`#{binary} -c 'from distutils import sysconfig; print(sysconfig.get_python_inc())'`.strip)
+    end
+  end
+
+  # Dir containing e.g. libpython2.7.dylib
+  def libdir
+    if brewed? || from_osx?
+      prefix/"lib/#{xy}/config"
+    else
+      Pathname.new(`#{binary} -c "from distutils import sysconfig; print(sysconfig.get_config_var('LIBPL'))"`.strip)
+    end
+  end
+
+  # Pkgconfig (pc) files of python
+  def pkg_config_path
+    if from_osx?
+      # No matter if CLT-only or Xcode-only, the pc file is always here on OS X:
+      path = Pathname.new("/System/Library/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/lib/pkgconfig")
+      path if path.exist?
+    else
+      prefix/"lib/pkgconfig"
+    end
+  end
+
+  # Is the Python brewed (and linked)?
+  def brewed?
+    @brewed ||= begin
+      require 'formula'
+      f = Formula.factory(@name)
+      f.installed? && f.linked_keg.exist?
+    end
+  end
+
+  # Is the python the one from OS X?
+  def from_osx?
+    @from_osx ||= begin
+      p = `#{binary} -c "import sys; print(sys.prefix)"`.strip
+      p.start_with?("/System/Library/Frameworks/Python.framework")
+    end
+  end
+
+  # Is the `python` a PyPy?
+  def pypy?
+    @pypy ||= !(`#{binary} -c "import sys; print(sys.version)"`.downcase =~ /.*pypy.*/).nil?
+  end
+
+  # Is this python a framework-style install (OS X only)?
+  def framework?
+    @framework ||= /Python[0-9]*\.framework/ === prefix.to_s
+  end
+
+  def universal?
+    @universal ||= archs_for_command(binary).universal?
+  end
+
+  def standard_caveats
+    if brewed?
+      ""  # empty string, so we can concat this
+    else
+      <<-EOS.undent
+        For non-homebrew #{@name} (#{@min_version.major}.x), you need to amend your PYTHONPATH like so:
+          export PYTHONPATH=#{global_site_packages}:$PYTHONPATH
+      EOS
+    end
+  end
+
+  def modify_build_environment
+    # Write our sitecustomize.py
+    file = global_site_packages/"sitecustomize.py"
+    ohai "Writing #{file}" if ARGV.verbose? || ARGV.homebrew_developer?
+    [".pyc", ".pyo", ".py"].map{ |f|
+      global_site_packages/"sitecustomize#{f}"
+    }.each{ |f| f.delete if f.exist? }
+    file.write(sitecustomize)
+
+    # For non-system python's we add the opt_prefix/bin of python to the path.
+    ENV.prepend 'PATH', binary.dirname, ':' unless from_osx?
+
+    ENV['PYTHONHOME'] = nil  # to avoid fuck-ups.
+    ENV['PYTHONNOUSERSITE'] = '1'
+    # Python respects the ARCHFLAGS var if set. Shall we set them here?
+    # ENV['ARCHFLAGS'] = ??? # FIXME
+    ENV.append 'CMAKE_INCLUDE_PATH', incdir, ':'
+    ENV.append 'PKG_CONFIG_PATH', pkg_config_path, ':' if pkg_config_path
+
+    # Udpate distutils.cfg (later we can remove this, but people still have
+    # their old brewed pythons and we have to update it here)
+    # Todo: If Jack's formula revisions arrive, we can get rid of this here!
+    if brewed?
+      require 'formula'
+      file = Formula.factory(@name).prefix/"Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/lib/#{xy}/distutils/distutils.cfg"
+      ohai "Writing #{file}" if ARGV.verbose? || ARGV.homebrew_developer?
+      file.delete if file.exist?
+      file.write <<-EOF.undent
+        [global]
+        verbose=1
+        [install]
+        force=1
+        prefix=#{HOMEBREW_PREFIX}
+      EOF
+    end
+  end
+
+  def sitecustomize
+    <<-EOF.undent
+      # This file is created by Homebrew and is executed on each python startup.
+      # Don't print from here, or else universe will collapse.
+      import sys
+
+      if sys.version_info.major == #{version.major} and sys.version_info.minor == #{version.minor}:
+          if sys.executable.startswith('#{HOMEBREW_PREFIX}'):
+              # Fix 1)
+              #   A setuptools.pth and/or easy-install.pth sitting either in
+              #   /Library/Python/2.7/site-packages or in
+              #   ~/Library/Python/2.7/site-packages can inject the
+              #   /System's Python site-packages. People then report
+              #   "OSError: [Errno 13] Permission denied" because pip/easy_install
+              #   attempts to install into
+              #   /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python
+              #   See: https://github.com/mxcl/homebrew/issues/14712
+              # Fix 2)
+              #   Remove brewed Python's hard-coded Cellar-site-packages
+              sys.path = [ p for p in sys.path
+                           if not (p.startswith('/System') or
+                                   p.startswith('#{HOMEBREW_PREFIX}/Cellar/python') and p.endswith('site-packages')) ]
+              # Fix 3)
+              # Set the sys.executable to use the opt_prefix
+              sys.executable = '#{HOMEBREW_PREFIX}/opt/#{name}/bin/python#{version.major}.#{version.minor}'
+              # Fix 4)
+              # Make LINKFORSHARED (and python-confing --ldflags) return the
+              # full path to the lib (yes, "Python" is actually the lib, not a
+              # dir) so that third-party software does not need to add the
+              # -F/#{HOMEBREW_PREFIX}/Frameworks switch.
+              # Assume Framework style build (default since months in brew)
+              try:
+                  from _sysconfigdata import build_time_vars
+                  build_time_vars['LINKFORSHARED'] = '-u _PyMac_Error #{HOMEBREW_PREFIX}/opt/#{name}/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/Python'
+              except:
+                  pass  # remember: don't print here. Better to fail silent.
+          # Fix 5)
+          #   For all Pythons of the right major.minor version: Tell about homebrew's
+          #   site-packages location. This is needed for Python to parse *.pth.
+          import site
+          site.addsitedir('#{global_site_packages}')
+    EOF
+  end
+
+  def message
+    @unsatisfied_because
+  end
+
+  def <=> other
+    version <=> other.version
+  end
+
+  def to_s
+    binary.to_s
+  end
+
+  def hash
+    to_s.hash
+  end
+end