Merge lp:~openstack-charmers/charm-helpers/os-alternatives into lp:charm-helpers

[James Page]

Alternatives helper to allow multiple charms to write the same configuration
files which priority determining which is to be used.

=== added file 'charmhelpers/contrib/openstack/alternatives.py'
--- charmhelpers/contrib/openstack/alternatives.py	1970-01-01 00:00:00 +0000
+++ charmhelpers/contrib/openstack/alternatives.py	2013-10-21 23:03:59 +0000
@@ -0,0 +1,17 @@
+''' Helper for managing alternatives for file conflict resolution '''
+
+import subprocess
+import shutil
+import os
+
+
+def install_alternative(name, target, source, priority=50):
+    ''' Install alternative configuration '''
+    if (os.path.exists(target) and not os.path.islink(target)):
+        # Move existing file/directory away before installing
+        shutil.move(target, '{}.bak'.format(target))
+    cmd = [
+        'update-alternatives', '--force', '--install',
+        target, name, source, str(priority)
+    ]
+    subprocess.check_call(cmd)
 
=== added file 'tests/contrib/openstack/test_alternatives.py'
--- tests/contrib/openstack/test_alternatives.py	1970-01-01 00:00:00 +0000
+++ tests/contrib/openstack/test_alternatives.py	2013-10-21 23:03:59 +0000
@@ -0,0 +1,68 @@
+from testtools import TestCase
+from mock import patch
+
+import charmhelpers.contrib.openstack.alternatives as alternatives
+
+
+NAME = 'test'
+SOURCE = '/var/lib/charm/test/test.conf'
+TARGET = '/etc/test/test,conf'
+
+
+class AlternativesTestCase(TestCase):
+
+    @patch('subprocess.os.path')
+    @patch('subprocess.check_call')
+    def test_new_alternative(self, _check, _path):
+        _path.exists.return_value = False
+        alternatives.install_alternative(NAME,
+                                         TARGET,
+                                         SOURCE)
+        _check.assert_called_with(
+            ['update-alternatives', '--force', '--install',
+             TARGET, NAME, SOURCE, '50']
+        )
+
+    @patch('subprocess.os.path')
+    @patch('subprocess.check_call')
+    def test_priority(self, _check, _path):
+        _path.exists.return_value = False
+        alternatives.install_alternative(NAME,
+                                         TARGET,
+                                         SOURCE, 100)
+        _check.assert_called_with(
+            ['update-alternatives', '--force', '--install',
+             TARGET, NAME, SOURCE, '100']
+        )
+
+    @patch('shutil.move')
+    @patch('subprocess.os.path')
+    @patch('subprocess.check_call')
+    def test_new_alternative_existing_file(self, _check,
+                                           _path, _move):
+        _path.exists.return_value = True
+        _path.islink.return_value = False
+        alternatives.install_alternative(NAME,
+                                         TARGET,
+                                         SOURCE)
+        _check.assert_called_with(
+            ['update-alternatives', '--force', '--install',
+             TARGET, NAME, SOURCE, '50']
+        )
+        _move.assert_called_with(TARGET, '{}.bak'.format(TARGET))
+
+    @patch('shutil.move')
+    @patch('subprocess.os.path')
+    @patch('subprocess.check_call')
+    def test_new_alternative_existing_link(self, _check,
+                                           _path, _move):
+        _path.exists.return_value = True
+        _path.islink.return_value = True
+        alternatives.install_alternative(NAME,
+                                         TARGET,
+                                         SOURCE)
+        _check.assert_called_with(
+            ['update-alternatives', '--force', '--install',
+             TARGET, NAME, SOURCE, '50']
+        )
+        _move.assert_not_called()