Hurray! Our first dependency processing bug! This is cool because it

means that people are finally doing enough things with setuptools to
have real-life version conflict scenarios.  Luckily, the fix is trivial:
use breadth-first instead of depth-first dependency processing, which I
thought we were already doing anyway, but weren't.  And we were giving
precedence to already-installed packages, which means upgrades didn't
work so well.

--HG--
branch : setuptools
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/trunk/setuptools%4041265

EasyInstall.txt

@@ -855,6 +855,13 @@ Known Issues
  * Improved Windows ``.exe`` script wrappers so that the script can have the
    same name as a module without confusing Python.
 
+ * Changed dependency processing so that it's breadth-first, allowing a
+   depender's preferences to override those of a dependee, to prevent conflicts
+   when a lower version is acceptable to the dependee, but not the depender.
+   Also, ensure that currently installed/selected packages aren't given
+   precedence over ones desired by a package being installed, which could
+   cause conflict errors.
+
 0.6a3
  * Improved error message when trying to use old ways of running
    ``easy_install``.  Removed the ability to run via ``python -m`` or by

pkg_resources.py

@@ -467,7 +467,7 @@ class WorkingSet(object):
         to_activate = []
 
         while requirements:
-            req = requirements.pop()
+            req = requirements.pop(0)   # process dependencies breadth-first
             if req in processed:
                 # Ignore cyclic or redundant dependencies
                 continue

pkg_resources.txt

@@ -1499,6 +1499,10 @@ Release Notes/Change History
    non-namespace modules have already been imported and issues a warning if
    a conflicting module has already been imported.
 
+ * Changed dependency processing so that it's breadth-first, allowing a
+   depender's preferences to override those of a dependee, to prevent conflicts
+   when a lower version is acceptable to the dependee, but not the depender.
+
 0.6a4
  * Fix a bug in ``WorkingSet.resolve()`` that was introduced in 0.6a3.
 

setuptools/command/easy_install.py

@@ -394,7 +394,7 @@ class easy_install(Command):
             return
 
         try:
-            WorkingSet(self.shadow_path).resolve(
+            WorkingSet([]).resolve(
                 [requirement], self.local_index, self.easy_install
             )
         except DistributionNotFound, e: