Handle loading plugins on demand.

Plugins that are referenced as dependencies, but have not been
registered now will be imported. Newer plugins should register
themselves automatically, but older style plugins will be
explicitly registered after import.

2 files changed, 44 insertions, 4 deletions

diff --git a/sleekxmpp/plugins/__init__.py b/sleekxmpp/plugins/__init__.py
index 4fb41919..8f8f851a 100644
--- a/sleekxmpp/plugins/__init__.py
+++ b/sleekxmpp/plugins/__init__.py
@@ -6,8 +6,9 @@
     See the file LICENSE for copying permission.
 """
 
-from sleekxmpp.plugins.base import PluginManager, PluginNotFound, \
-                                   BasePlugin, register_plugin
+from sleekxmpp.plugins.base import PluginManager, PluginNotFound, BasePlugin
+from sleekxmpp.plugins.base import register_plugin, load_plugin
+
 
 __all__ = [
     # Non-standard
diff --git a/sleekxmpp/plugins/base.py b/sleekxmpp/plugins/base.py
index 447ffba7..bc0504ea 100644
--- a/sleekxmpp/plugins/base.py
+++ b/sleekxmpp/plugins/base.py
@@ -33,6 +33,10 @@ PLUGIN_DEPENDENTS = {}
 REGISTRY_LOCK = threading.RLock()
 
 
+class PluginNotFound(Exception):
+    """Raised if an unknown plugin is accessed."""
+
+
 def register_plugin(impl, name=None):
     """Add a new plugin implementation to the registry.
 
@@ -56,8 +60,40 @@ def register_plugin(impl, name=None):
             PLUGIN_DEPENDENTS[dep].add(name)
 
 
-class PluginNotFound(Exception):
-    """Raised if an unknown plugin is accessed."""
+def load_plugin(name, module=None):
+    """Find and import a plugin module so that it can be registered.
+
+    This function is called to import plugins that have selected for
+    enabling, but no matching registered plugin has been found.
+
+    :param str name: The name of the plugin. It is expected that
+                     plugins are in packages matching their name,
+                     even though the plugin class name does not
+                     have to match.
+    :param str module: The name of the base module to search 
+                       for the plugin.
+    """
+    try:
+        if not module:
+            try:
+                module = 'sleekxmpp.plugins.%s' % name
+                mod = __import__(module, fromlist=[str(name)])
+            except:
+                module = 'sleekxmpp.features.%s' % name
+                mod = __import__(module, fromlist=[str(name)])
+        else:
+            mod = __import__(module, fromlist=[str(name)])
+
+        # Add older style plugins to the registry.
+        if hasattr(mod, name):
+            plugin = getattr(mod, name)
+            if not hasattr(plugin, 'name'):
+                plugin.name = name
+            register_plugin(plugin, name)
+        else:
+            log.debug("%s does not have %s", mod, name)
+    except:
+        log.exception("Unable to load plugin: %s", name)
 
 
 class PluginManager(object): 
@@ -105,6 +141,9 @@ class PluginManager(object):
             if name not in self._enabled:
                 enabled.add(name)
                 self._enabled.add(name)
+                if not self.registered(name):
+                    load_plugin(name)
+
                 plugin_class = PLUGIN_REGISTRY.get(name, None)
                 if not plugin_class:
                     raise PluginNotFound(name)