Merge branch 'master' into feature/implicit-bootstrapfeature/implicit-bootstrap

1 files changed, 43 insertions, 2 deletions

diff --git a/setup.py b/setup.py
index 7d6bd06b..0dab158d 100755
--- a/setup.py
+++ b/setup.py
@@ -5,9 +5,11 @@ Distutils setup file, used to install or test 'setuptools'
 
 import os
 import sys
+import textwrap
 
-import setuptools
 import bootstrap
+import setuptools
+from setuptools.command.install import install
 
 here = os.path.dirname(__file__)
 
@@ -71,8 +73,48 @@ def pypi_link(pkg_filename):
     return '/'.join(parts)
 
 
+class install_with_pth(install):
+    """
+    Custom install command to install a .pth file for distutils patching.
+
+    This hack is necessary because there's no standard way to install behavior
+    on startup (and it's debatable if there should be one). This hack (ab)uses
+    the `extra_path` behavior in Setuptools to install a `.pth` file with
+    implicit behavior on startup to give higher precedence to the local version
+    of `distutils` over the version from the standard library.
+
+    Please do not replicate this behavior.
+    """
+
+    _pth_name = 'distutils-precedence'
+    _pth_contents = textwrap.dedent("""
+        import os
+        var = 'SETUPTOOLS_USE_DISTUTILS'
+        enabled = os.environ.get(var, 'stdlib') == 'local'
+        enabled and __import__('_distutils_hack').add_shim()
+        """).lstrip().replace('\n', '; ')
+
+    def initialize_options(self):
+        install.initialize_options(self)
+        self.extra_path = self._pth_name, self._pth_contents
+
+    def finalize_options(self):
+        install.finalize_options(self)
+        self._restore_install_lib()
+
+    def _restore_install_lib(self):
+        """
+        Undo secondary effect of `extra_path` adding to `install_lib`
+        """
+        suffix = os.path.relpath(self.install_lib, self.install_libbase)
+
+        if suffix.strip() == self._pth_contents.strip():
+            self.install_lib = self.install_libbase
+
+
 setup_params = dict(
     src_root=None,
+    cmdclass={'install': install_with_pth},
     package_data=package_data,
     entry_points={
         "distutils.commands": [
@@ -81,7 +123,6 @@ setup_params = dict(
         ],
         "setuptools.finalize_distribution_options": [
             "parent_finalize = setuptools.dist:_Distribution.finalize_options",
-            "features = setuptools.dist:Distribution._finalize_feature_opts",
             "keywords = setuptools.dist:Distribution._finalize_setup_keywords",
             "2to3_doctests = "
             "setuptools.dist:Distribution._finalize_2to3_doctests",