plumb in a native toolchain subsystem

src/python/pants/backend/python/subsystems/python_native_toolchain.py

@@ -0,0 +1,60 @@
+# coding=utf-8
+# Copyright 2014 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+from pants.binaries.binary_util import BinaryUtil
+from pants.subsystem.subsystem import Subsystem
+from pants.util.memo import memoized_property
+
+
+class PythonNativeToolchain(object):
+  """Represents a self-boostrapping set of binaries and libraries used to
+  compile native code in for python dists."""
+
+  class Factory(Subsystem):
+    options_scope = 'python-native-toolchain'
+
+    @classmethod
+    def subsystem_dependencies(cls):
+      return (BinaryUtil.Factory,)
+
+    @classmethod
+    def register_options(cls, register):
+      register('--supportdir', advanced=True,
+               help='Find the go distributions under this dir.  Used as part '
+                    'of the path to lookup the distribution with '
+                    '--binary-util-baseurls and --pants-bootstrapdir',
+               default='bin/python-native-toolchain')
+      register('--clang-version', advanced=True,
+               help='Clang version used to compile python native extensions.  '
+                    'Used as part of the path to lookup the distribution '
+                    'with --binary-util-baseurls and --pants-bootstrapdir',
+               default='5.0.0')
+
+    # NB: create() is an instance method to allow the user to choose global or
+    # scoped -- It's not unreasonable to imagine different stacks for different
+    # python versions. Get an instance of this with
+    # PythonNativeToolchain.Factory.scoped_instance(self).create()!
+    def create(self):
+      binary_util = BinaryUtil.Factory.create()
+      options = self.get_options()
+      return PythonNativeToolchain(binary_util=binary_util,
+                                   relpath=options.supportdir,
+                                   clang_version=options.clang_version)
+
+  def __init__(self, binary_util, relpath, clang_version):
+    self._binary_util = binary_util
+    self._relpath = relpath
+    self._clang_version = clang_version
+
+  @property
+  def clang_version(self):
+    return self._clang_version
+
+  @memoized_property
+  def clang_path(self):
+    return self._binary_util.select_binary(
+      self._relpath, self.clang_version, 'clang')

src/python/pants/backend/python/tasks/build_local_python_distributions.py

@@ -13,6 +13,7 @@
 
 from pex.interpreter import PythonInterpreter
 
+from pants.backend.python.subsystems.python_native_toolchain import PythonNativeToolchain
 from pants.backend.python.tasks.pex_build_util import is_local_python_dist
 from pants.backend.python.tasks.setup_py import SetupPyRunner
 from pants.base.build_environment import get_buildroot
@@ -21,6 +22,7 @@
 from pants.task.task import Task
 from pants.util.contextutil import environment_as, temporary_dir
 from pants.util.dirutil import safe_mkdir
+from pants.util.memo import memoized_property
 
 
 PANTSSETUP_IMPORT_BOILERPLATE = """
@@ -48,6 +50,14 @@ def product_types(cls):
   def prepare(cls, options, round_manager):
     round_manager.require_data(PythonInterpreter)
 
+  @classmethod
+  def subsystem_dependencies(cls):
+    return super(BuildLocalPythonDistributions, cls).subsystem_dependencies() + (PythonNativeToolchain.Factory,)
+
+  @memoized_property
+  def python_native_toolchain(self):
+    return PythonNativeToolchain.Factory.scoped_instance(self).create()
+
   @property
   def cache_target_dirs(self):
     return True