plugable: remember overriden plugins in API

Remember what plugin class was overriden by what plugin class in API
objects. Add new method API.get_plugin_next which returns the plugin
class which was overriden by the plugin class specified as argument.

https://fedorahosted.org/freeipa/ticket/4739

Reviewed-By: David Kupka <dkupka@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/ipalib/plugable.py b/ipalib/plugable.py
index ed63ec646..b248a2c28 100644
--- a/ipalib/plugable.py
+++ b/ipalib/plugable.py
@@ -267,6 +267,7 @@ class API(ReadOnly):
     def __init__(self):
         super(API, self).__init__()
         self.__plugins = {}
+        self.__next = {}
         self.__done = set()
         self.env = Env()
 
@@ -593,6 +594,8 @@ class API(ReadOnly):
                     name=klass.__name__,
                     plugin=klass,
                 )
+
+            self.__next[klass] = prev
         else:
             if override:
                 # There was nothing already registered to override:
@@ -653,6 +656,12 @@ class API(ReadOnly):
         if not production_mode:
             lock(self)
 
+    def get_plugin_next(self, klass):
+        if not inspect.isclass(klass):
+            raise TypeError('plugin must be a class; got %r' % klass)
+
+        return self.__next[klass]
+
 
 class IPAHelpFormatter(optparse.IndentedHelpFormatter):
     def format_epilog(self, text):