From: Zac Medico <zmedico@gentoo.org>
Date: Wed, 6 Oct 2010 20:13:16 +0000 (-0700)
Subject: Optimize slot conflict backtracking for #337178.
X-Git-Tag: v2.2_rc90~2
X-Git-Url: http://git.tremily.us/gitweb.cgi?a=commitdiff_plain;h=beeac7feedb90a9e93169390a4fa3116a0e247b6;p=portage.git

Optimize slot conflict backtracking for #337178.

This borrows logic from commit
fc33f34e3d060b57e03204fb427b01971f8dafff which fixes bug #337178
in the 2.1.9 branch. With this change,
BacktrackingTestCase.testBacktrackingGoodVersionFirst() is solved
with one less backtracking step.
---

diff --git a/pym/_emerge/depgraph.py b/pym/_emerge/depgraph.py
index 5ab42f68e..846d3ece5 100644
--- a/pym/_emerge/depgraph.py
+++ b/pym/_emerge/depgraph.py
@@ -924,6 +924,19 @@ class depgraph(object):
 							# behavior if this gets triggered somehow.
 							backtrack_data = fallback_data
 
+						if len(backtrack_data) > 1:
+							# NOTE: Generally, we prefer to mask the higher
+							# version since this solves common cases in which a
+							# lower version is needed so that all dependencies
+							# will be satisfied (bug #337178). However, if
+							# existing_node happens to be installed then we
+							# mask that since this is a common case that is
+							# triggered when --update is not enabled.
+							if existing_node.installed:
+								pass
+							elif pkg > existing_node:
+								backtrack_data.reverse()
+
 						to_be_masked = backtrack_data[-1][0]
 
 						self._dynamic_config._backtrack_infos["slot conflict"] = backtrack_data