Create PluginClassRegistry class to handle class loading/unloading

Implements signals emitted when a plugin class is loaded/unloaded and
defers registration of classes until the plugin module is fully loaded.

src/mcedit2/editortools/generate.py

@@ -10,6 +10,7 @@ from PySide import QtCore, QtGui
 from mcedit2.command import SimpleRevisionCommand
 from mcedit2.editortools import EditorTool
 from mcedit2.handles.boxhandle import BoxHandle
+from mcedit2.plugins.registry import PluginClassRegistry
 from mcedit2.rendering.scenegraph import scenenode
 from mcedit2.rendering.scenegraph.matrix import Translate
 from mcedit2.rendering.scenegraph.scenenode import Node
@@ -134,24 +135,11 @@ class GeneratePlugin(QtCore.QObject):
     def editorSession(self):
         return self.generateTool.editorSession
 
-_pluginClasses = []
 
+class _GeneratePlugins(PluginClassRegistry):
+    pluginClass = GeneratePlugin
 
-def registerGeneratePlugin(cls):
-    _pluginClasses.append(cls)
-    _GeneratePlugins.instance.pluginAdded.emit(cls)
-    return cls
-
-
-def unregisterGeneratePlugin(cls):
-    _pluginClasses[:] = [c for c in _pluginClasses if c != cls]
-    _GeneratePlugins.instance.pluginRemoved.emit(cls)
-
-class _GeneratePlugins(QtCore.QObject):
-    pluginRemoved = QtCore.Signal(object)
-    pluginAdded = QtCore.Signal(object)
-
-_GeneratePlugins.instance = _GeneratePlugins()
+GeneratePlugins = _GeneratePlugins()
 
 
 class GenerateTool(EditorTool):
@@ -171,7 +159,7 @@ class GenerateTool(EditorTool):
         self.toolWidget = toolWidget
 
         column = []
-        self.generatorTypes = [pluginClass(self) for pluginClass in _pluginClasses]
+        self.generatorTypes = [pluginClass(self) for pluginClass in GeneratePlugins.registeredPlugins]
         self.currentGenerator = None
         if len(self.generatorTypes):
             self.currentGenerator = self.generatorTypes[0]
@@ -236,8 +224,8 @@ class GenerateTool(EditorTool):
         # so it can be reselected if it is immediately reloaded
         self._lastTypeName = None
 
-        _GeneratePlugins.instance.pluginAdded.connect(self.addPlugin)
-        _GeneratePlugins.instance.pluginRemoved.connect(self.removePlugin)
+        GeneratePlugins.pluginAdded.connect(self.addPlugin)
+        GeneratePlugins.pluginRemoved.connect(self.removePlugin)
 
     def removePlugin(self, cls):
         log.info("Removing plugin %s", cls.__name__)

src/mcedit2/plugins/__init__.py

@@ -2,11 +2,13 @@
     plugins
 """
 from __future__ import absolute_import, division, print_function
-from collections import defaultdict
-import logging
-import itertools
-import os
+
 import imp
+import itertools
+import logging
+import os
+from collections import defaultdict
+
 from mcedit2 import editortools
 from mcedit2.editortools import generate
 from mcedit2.plugins import command
@@ -115,9 +117,15 @@ class PluginRef(object):
             _currentPluginPathname = pathname
 
             self.pluginModule = imp.load_module(basename, io, pathname, description)
-            self.registerModule()
+            _loadedModules[self.fullpath] = self.pluginModule
+            self.pluginModule.__FOUND_FILENAME__ = self.fullpath
+
             _currentPluginPathname = None
 
+            # Plugin registration is deferred until the module is fully loaded.
+            for registry in _registries:
+                registry.commitRegistrations()
+
             if hasattr(self.pluginModule, 'displayName'):
                 self._displayName = self.pluginModule.displayName
 
@@ -134,19 +142,14 @@ class PluginRef(object):
 
         return True
 
-    def registerModule(self):
-        module = self.pluginModule
-    
-        _loadedModules[self.fullpath] = module
-        module.__FOUND_FILENAME__ = self.fullpath
-
     def unload(self):
         if self.pluginModule is None:
             return
         module = self.pluginModule
 
         try:
-            self.unregisterModule()
+            if hasattr(module, "unregister"):
+                module.unregister()
 
         except Exception as e:
             self.unloadError = sys.exc_info()
@@ -156,24 +159,24 @@ class PluginRef(object):
             self.unloadError = None
         finally:
             self.pluginModule = None
+            deadKeys = []
             for k, v in sys.modules.iteritems():
                 if v is module:
+                    deadKeys.append(k)
+
+            for k in deadKeys:
                 sys.modules.pop(k)
                 log.info("Removed module %s from sys.modules", k)
 
-        return True
-
-    def unregisterModule(self):
-        module = self.pluginModule
-        if hasattr(module, "unregister"):
-            module.unregister()
-
             classes = _pluginClassesByPathname.pop(self.fullpath)
             if classes:
                 for cls in classes:
                     _unregisterClass(cls)
 
             _loadedModules.pop(module.__FOUND_FILENAME__)
+            self.fullpath = None
+
+        return True
 
     @property
     def isLoaded(self):
@@ -256,6 +259,10 @@ _loadedModules = {}
 _pluginClassesByPathname = defaultdict(list)
 _currentPluginPathname = None
 
+_registries = [
+    command.CommandPlugins,
+    generate.GeneratePlugins
+]
 
 def _registerClass(cls):
     _pluginClassesByPathname[_currentPluginPathname].append(cls)
@@ -265,10 +272,11 @@ def _registerClass(cls):
 def _unregisterClass(cls):
     load_ui.unregisterCustomWidget(cls)
     editortools.unregisterToolClass(cls)
-    generate.unregisterGeneratePlugin(cls)
     inspector.unregisterBlockInspectorWidget(cls)
     entities.unregisterTileEntityRefClass(cls)
-    command.unregisterPluginCommand(cls)
+
+    generate.GeneratePlugins.unregisterClass(cls)
+    command.CommandPlugins.unregisterClass(cls)
 
 # --- Registration functions ---
 
@@ -290,7 +298,7 @@ def registerPluginCommand(cls):
     cls : Class
     """
     _registerClass(cls)
-    return command.registerPluginCommand(cls)
+    return command.CommandPlugins.registerClass(cls)
 
 
 def registerCustomWidget(cls):
@@ -354,7 +362,7 @@ def registerGeneratePlugin(cls):
     cls : Class
     """
     _registerClass(cls)
-    return generate.registerGeneratePlugin(cls)
+    return generate.GeneratePlugins.registerClass(cls)
 
 def registerBlockInspectorWidget(cls):
     """

src/mcedit2/plugins/command.py

@@ -7,6 +7,8 @@ from collections import defaultdict
 
 from PySide import QtCore, QtGui
 
+from mcedit2.plugins.registry import PluginClassRegistry
+
 log = logging.getLogger(__name__)
 
 
@@ -52,28 +54,10 @@ class PluginCommand(QtCore.QObject):
         self.editorSession.menuPlugins.addPluginMenuItem(self.__class__, text, func, submenu)
 
 
-class _CommandPlugins(QtCore.QObject):
-    pluginRemoved = QtCore.Signal(object)
-    pluginAdded = QtCore.Signal(object)
+class _CommandPlugins(PluginClassRegistry):
+    pluginClass = PluginCommand
 
-_CommandPlugins.instance = _CommandPlugins()
-
-_registeredCommands = []
-
-
-def registerPluginCommand(cls):
-    if issubclass(cls, PluginCommand):
-        _registeredCommands.append(cls)
-    else:
-        raise ValueError("Class %s must inherit from PluginCommand" % cls)
-
-    _CommandPlugins.instance.pluginAdded.emit(cls)
-    return cls
-
-
-def unregisterPluginCommand(cls):
-    if issubclass(cls, PluginCommand):
-        _CommandPlugins.instance.pluginRemoved.emit(cls)
+CommandPlugins = _CommandPlugins()
 
 
 class PluginsMenu(QtGui.QMenu):
@@ -82,14 +66,14 @@ class PluginsMenu(QtGui.QMenu):
         self.setTitle(self.tr("Plugins"))
         self.editorSession = editorSession
         self.submenus = {}
-        _CommandPlugins.instance.pluginRemoved.connect(self.pluginRemoved)
-        _CommandPlugins.instance.pluginAdded.connect(self.pluginAdded)
+        CommandPlugins.pluginRemoved.connect(self.pluginRemoved)
+        CommandPlugins.pluginAdded.connect(self.pluginAdded)
         self.plugins = []
 
         self.actionsByClass = defaultdict(list)
 
     def loadPlugins(self):
-        for cls in _registeredCommands:
+        for cls in CommandPlugins.registeredPlugins:
             instance = cls(self.editorSession)
             self.plugins.append(instance)
 
@@ -119,5 +103,5 @@ class PluginsMenu(QtGui.QMenu):
         action = menu.addAction(text, func)
 
         self.actionsByClass[cls].append(action)
-        log.info("Added action %s")
+        log.info("Added action %s", action)
         return action

src/mcedit2/plugins/registry.py

@@ -0,0 +1,38 @@
+"""
+    registry
+"""
+from __future__ import absolute_import, division, print_function, unicode_literals
+import logging
+
+from PySide import QtCore
+
+log = logging.getLogger(__name__)
+
+
+class PluginClassRegistry(QtCore.QObject):
+    pluginRemoved = QtCore.Signal(object)
+    pluginAdded = QtCore.Signal(object)
+
+    pluginClass = NotImplemented
+
+    def __init__(self):
+        super(PluginClassRegistry, self).__init__()
+        self.pendingRegistrations = []
+        self.registeredPlugins = []
+
+    def commitRegistrations(self):
+        for cls in self.pendingRegistrations:
+            self.registeredPlugins.append(cls)
+            self.pluginAdded.emit(cls)
+        self.pendingRegistrations[:] = []
+
+    def registerClass(self, cls):
+        if issubclass(cls, self.pluginClass):
+            self.pendingRegistrations.append(cls)
+        else:
+            raise ValueError("Class %s must inherit from PluginCommand" % cls)
+        return cls
+
+    def unregisterClass(self, cls):
+        if issubclass(cls, self.pluginClass):
+            self.pluginRemoved.emit(cls)