Rules: New options replace_name to replace %{name} in attributes

If you use the regex feature of Rules/Defaults you may need the real name
of the matched entry in an attribute (for example home of POSIXUser).
You can now enable replace_name for rules or defaults and %{name} will be
replaces in the attribues of the Element before adding them to the target
entry.

This allows you to write something like that in Defaults to assing a default
home directory somewhere else to all users with unset home:

    <POSIXUser name='.*' home='/somewhere/%{name}'/>

1 files changed, 26 insertions, 1 deletions

diff --git a/src/lib/Bcfg2/Server/Plugins/Rules.py b/src/lib/Bcfg2/Server/Plugins/Rules.py
index a3f682ed6..cf659251c 100644
--- a/src/lib/Bcfg2/Server/Plugins/Rules.py
+++ b/src/lib/Bcfg2/Server/Plugins/Rules.py
@@ -1,10 +1,17 @@
 """This generator provides rule-based entry mappings."""
 
+import copy
 import re
+import string
 import Bcfg2.Options
 import Bcfg2.Server.Plugin
 
 
+class NameTemplate(string.Template):
+    """Simple subclass of string.Template with a custom delimiter."""
+    delimiter = '%'
+
+
 class Rules(Bcfg2.Server.Plugin.PrioDir):
     """This is a generator that handles service assignments."""
     __author__ = 'bcfg-dev@mcs.anl.gov'
@@ -12,7 +19,10 @@ class Rules(Bcfg2.Server.Plugin.PrioDir):
     options = Bcfg2.Server.Plugin.PrioDir.options + [
         Bcfg2.Options.BooleanOption(
             cf=("rules", "regex"), dest="rules_regex",
-            help="Allow regular expressions in Rules")]
+            help="Allow regular expressions in Rules"),
+        Bcfg2.Options.BooleanOption(
+            cf=("rules", "replace_name"), dest="rules_replace_name",
+            help="Replace %{name} in attributes with name of target entry")]
 
     def __init__(self, core):
         Bcfg2.Server.Plugin.PrioDir.__init__(self, core)
@@ -46,7 +56,22 @@ class Rules(Bcfg2.Server.Plugin.PrioDir):
                 return True
         return False
 
+    def _apply(self, entry, data):
+        if self._replace_name_enabled:
+            data = copy.deepcopy(data)
+            for key, val in list(data.attrib.items()):
+                data.attrib[key] = NameTemplate(val).safe_substitute(
+                    name=entry.get('name'))
+
+        Bcfg2.Server.Plugin.PrioDir._apply(self, entry, data)
+
     @property
     def _regex_enabled(self):
         """ Return True if rules regexes are enabled, False otherwise """
         return Bcfg2.Options.setup.rules_regex
+
+    @property
+    def _replace_name_enabled(self):
+        """ Return True if the replace_name feature is enabled,
+        False otherwise """
+        return Bcfg2.Options.setup.rules_replace_name