return plugins in order specified by config

ckan/plugins/core.py

@@ -5,12 +5,16 @@
 import logging
 from inspect import isclass
 from itertools import chain
+from operator import itemgetter
 from pkg_resources import iter_entry_points
+
 from pyutilib.component.core import PluginGlobals, implements
-from pyutilib.component.core import ExtensionPoint as PluginImplementations
+from pyutilib.component.core import ExtensionPoint
 from pyutilib.component.core import SingletonPlugin as _pca_SingletonPlugin
 from pyutilib.component.core import Plugin as _pca_Plugin
 
+from pylons import config
+
 from ckan.plugins.interfaces import IPluginObserver
 
 __all__ = [
@@ -29,6 +33,31 @@
 # not need to be explicitly enabled by the user)
 SYSTEM_PLUGINS_ENTRY_POINT_GROUP = "ckan.system_plugins"
 
+# _plugins_info and _plugins_index are used in ordering plugins
+_plugins_info = {}
+_plugins_index = 0
+
+
+class PluginImplementations(ExtensionPoint):
+    ''' This is a cusomised version of pyutilib ExtensionPoint that
+    returns the plugins in the order specified by the ckan config.
+
+    Usage::
+
+        >>> plugins = PluginImplementations(IMapper)
+        ... # plugins is a list of plugins implementing IMapper
+
+    '''
+
+    def extensions(self, all=False, key=None):
+        plugins = super(PluginImplementations, self) \
+            .extensions(all=all, key=key)
+        ordered = []
+        for plugin in plugins:
+            ordered.append([plugin, _plugins_info[plugin.__class__]])
+        ordered = [x[0] for x in sorted(ordered, key=itemgetter(1, 0))]
+        return ordered
+
 
 class PluginNotFoundException(Exception):
     """
@@ -90,6 +119,12 @@ def load_all(config):
     """
     Load all plugins listed in the 'ckan.plugins' config directive.
     """
+
+    global _plugins_info
+    _plugins_info = {}
+    global _plugins_index
+    _plugins_index = 0
+
     plugins = chain(
         find_system_plugins(),
         find_user_plugins(config)
@@ -108,7 +143,6 @@ def reset():
     """
     Clear and reload all configured plugins
     """
-    from pylons import config
     load_all(config)
 
 
@@ -157,14 +191,21 @@ def find_user_plugins(config):
     Return all plugins specified by the user in the 'ckan.plugins' config
     directive.
     """
+    global _plugins_index
+    global _plugins_info
+
     plugins = []
     for name in config.get('ckan.plugins', '').split():
         entry_points = list(
             iter_entry_points(group=PLUGINS_ENTRY_POINT_GROUP, name=name)
         )
         if not entry_points:
             raise PluginNotFoundException(name)
-        plugins.extend(ep.load() for ep in entry_points)
+        loaded_plugins = (ep.load() for ep in entry_points)
+        for x in loaded_plugins:
+            plugins.append(x)
+            _plugins_info[x] = _plugins_index
+        _plugins_index += 1
     return plugins
 
 
@@ -175,7 +216,14 @@ def find_system_plugins():
     These are essential for operation and therefore cannot be enabled/disabled
     through the configuration file.
     """
-    return (
-        ep.load()
-        for ep in iter_entry_points(group=SYSTEM_PLUGINS_ENTRY_POINT_GROUP)
-    )
+    global _plugins_index
+    global _plugins_info
+
+    plugins = []
+    entry_points = iter_entry_points(group=SYSTEM_PLUGINS_ENTRY_POINT_GROUP)
+    loaded_plugins = (ep.load() for ep in entry_points)
+    for x in loaded_plugins:
+        plugins.append(x)
+        _plugins_info[x] = _plugins_index
+        _plugins_index += 1
+    return plugins