Allow ``ez_setup.use_setuptools()`` to upgrade existing setuptools

installations when called from a standalone ``setup.py``. (backport
from trunk)

--HG--
branch : setuptools-0.6
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/branches/setuptools-0.6%4060813

1 files changed, 58 insertions, 23 deletions

diff --git a/ez_setup.py b/ez_setup.py
index 11def6ab..6c5d5050 100755
--- a/ez_setup.py
+++ b/ez_setup.py
@@ -77,31 +77,31 @@ def use_setuptools(
     this routine will print a message to ``sys.stderr`` and raise SystemExit in
     an attempt to abort the calling script.
     """
-    try:
-        import setuptools
-        if setuptools.__version__ == '0.0.1':
-            print >>sys.stderr, (
-            "You have an obsolete version of setuptools installed.  Please\n"
-            "remove it from your system entirely before rerunning this script."
-            )
-            sys.exit(2)
-    except ImportError:
+    was_imported = 'pkg_resources' in sys.modules or 'setuptools' in sys.modules
+    def do_download():
         egg = download_setuptools(version, download_base, to_dir, download_delay)
         sys.path.insert(0, egg)
         import setuptools; setuptools.bootstrap_install_from = egg
-
-    import pkg_resources
     try:
-        pkg_resources.require("setuptools>="+version)
-
+        import pkg_resources
+    except ImportError:
+        return do_download()       
+    try:
+        pkg_resources.require("setuptools>="+version); return
     except pkg_resources.VersionConflict, e:
-        # XXX could we install in a subprocess here?
-        print >>sys.stderr, (
+        if was_imported:
+            print >>sys.stderr, (
             "The required version of setuptools (>=%s) is not available, and\n"
             "can't be installed while this script is running. Please install\n"
-            " a more recent version first.\n\n(Currently using %r)"
-        ) % (version, e.args[0])
-        sys.exit(2)
+            " a more recent version first, using 'easy_install -U setuptools'."
+            "\n\n(Currently using %r)"
+            ) % (version, e.args[0])
+            sys.exit(2)
+        else:
+            del pkg_resources, sys.modules['pkg_resources']    # reload ok
+            return do_download()
+    except pkg_resources.DistributionNotFound:
+        return do_download()
 
 def download_setuptools(
     version=DEFAULT_VERSION, download_base=DEFAULT_URL, to_dir=os.curdir,
@@ -150,9 +150,43 @@ and place it in this directory before rerunning this script.)
             if dst: dst.close()
     return os.path.realpath(saveto)
 
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 def main(argv, version=DEFAULT_VERSION):
     """Install or upgrade setuptools and EasyInstall"""
-
     try:
         import setuptools
     except ImportError:
@@ -167,8 +201,11 @@ def main(argv, version=DEFAULT_VERSION):
                 os.unlink(egg)
     else:
         if setuptools.__version__ == '0.0.1':
-            # tell the user to uninstall obsolete version
-            use_setuptools(version)
+            print >>sys.stderr, (
+            "You have an obsolete version of setuptools installed.  Please\n"
+            "remove it from your system entirely before rerunning this script."
+            )
+            sys.exit(2)
 
     req = "setuptools>="+version
     import pkg_resources
@@ -189,8 +226,6 @@ def main(argv, version=DEFAULT_VERSION):
             print "Setuptools version",version,"or greater has been installed."
             print '(Run "ez_setup.py -U setuptools" to reinstall or upgrade.)'
 
-
-
 def update_md5(filenames):
     """Update our built-in md5 registry"""