making ez_setup removing an existing setuptools distribution out of the way

--HG--
branch : distribute
extra : rebase_source : a97ad8f22e698747b81a097215b8ebffdf7edae6

ez_setup.py

@@ -14,7 +14,7 @@ the appropriate options to ``use_setuptools()``.
 This file can also be run as a script to install or upgrade setuptools.
 """
 import sys
-import sys, os
+import os
 try:
     from hashlib import md5
 except ImportError:
@@ -133,6 +133,34 @@ def main(argv, version=DEFAULT_VERSION):
     """Install or upgrade setuptools and EasyInstall"""
     try:
         import setuptools
+        # we need to check if the installed setuptools
+        # is from Distribute or from setuptools
+        if not hasattr(setuptools, '_distribute'):
+            # we have a setuptools distribution, we need to get out
+            # of our way. This is done by removing all references
+            # of setuptools egg from .pth files.
+
+            # removing setuptools distribution from easy_install.pth
+            # using the --multi-version option seems like the safest
+            # way to do this.
+            from setuptools.command.easy_install import main
+            main(['-q', '-m', 'setuptools'])
+
+            # now removing setuptool.pth manually so installing
+            # 'distribute' will re-create it. Notice that a -U call
+            # will have the same effect.
+            from setuptools.command.easy_install import easy_install
+            from setuptools.dist import Distribution
+            dist = Distribution()
+            cmd = easy_install(dist)
+            cmd.args = ['setuptools']
+            cmd.ensure_finalized()
+            pth_file = os.path.join(cmd.install_dir, 'setuptools.pth')
+            if os.path.exists(pth_file):
+                os.remove(pth_file)
+
+            # now we are ready to install distribute
+            raise ImportError
     except ImportError:
         egg = None
         try:

setuptools/__init__.py

@@ -13,6 +13,15 @@ __all__ = [
     'find_packages'
 ]
 
+# This marker is used to simplify the process that checks is the
+# setuptools package was installed by the Setuptools project
+# or by the Distribute project, in case Setuptools creates
+# a distribution with the same version.
+#
+# The ez_setup script for instance, will check if this
+# attribute is present to decide wether to reinstall the package
+_distribute = True
+
 bootstrap_install_from = None
 
 def find_packages(where='.', exclude=()):

setuptools/command/easy_install.py

@@ -969,8 +969,7 @@ See the setuptools documentation for the "develop" command for more info.
         if not self.dry_run:
 
             self.pth_file.save()
-
-            if dist.key=='setuptools':
+            if dist.key=='distribute':
                 # Ensure that setuptools itself never becomes unavailable!
                 # XXX should this check for latest version?
                 filename = os.path.join(self.install_dir,'setuptools.pth')