Add a plugin infrastructure

jedi/evaluate/__init__.py

@@ -108,6 +108,8 @@ class Evaluator(object):
 
         self.reset_recursion_limitations()
         self.allow_different_encoding = True
+        from jedi.plugins import plugin_manager
+        self.plugin_callbacks = plugin_manager.get_callbacks(self)
 
     @property
     @evaluator_function_cache()

jedi/evaluate/base_context.py

@@ -53,17 +53,17 @@ class Context(BaseContext):
         except stdlib.NotInStdLib:
             pass
 
-        try:
-            func = self.py__call__
-        except AttributeError:
-            debug.warning("no execution possible %s", self)
-            return NO_CONTEXTS
-        else:
-            context_set = func(arguments)
-            debug.dbg('execute result: %s in %s', context_set, self)
-            return context_set
-
-        return self.evaluator.execute(self, arguments)
+        def default(arguments):
+            try:
+                func = self.py__call__
+            except AttributeError:
+                debug.warning("no execution possible %s", self)
+                return NO_CONTEXTS
+            else:
+                context_set = func(arguments)
+                debug.dbg('execute result: %s in %s', context_set, self)
+                return context_set
+        return self.evaluator.plugin_callbacks.execute(default, arguments)
 
     def execute_evaluated(self, *value_list):
         """

jedi/plugins/__init__.py

@@ -0,0 +1,43 @@
+from functools import partial
+
+
+class _PluginManager(object):
+    def __init__(self, registered_plugin_classes=()):
+        self._registered_plugin_classes = list(registered_plugin_classes)
+
+    def register(self, plugin_class):
+        """
+        Makes it possible to register your plugin.
+        """
+        self._registered_plugins.append(plugin_class)
+
+    def _build_chain(self, evaluator):
+        for plugin_class in self._registered_plugin_classes:
+            yield plugin_class(evaluator)
+
+    def get_callbacks(self, evaluator):
+        return _PluginCallbacks(self._build_chain(evaluator))
+
+
+class _PluginCallbacks(object):
+    def __init__(self, plugins):
+        plugins = list(plugins)
+        self.execute = self._wrap(plugins, 'execute')
+
+    def _wrap(self, plugins, name):
+        if not plugins:
+            def default_callback(callback, *args, **kwargs):
+                return callback(*args, **kwargs)
+
+            return default_callback
+
+        func = None
+        for plugin in plugins:
+            if func is None:
+                func = getattr(plugin, name)
+            else:
+                func = partial(getattr(plugin, name), func)
+        return func
+
+
+plugin_manager = _PluginManager()

jedi/plugins/base.py

@@ -0,0 +1,10 @@
+class BasePlugin(object):
+    """
+    Plugins are created each time an evaluator is created.
+    """
+    def __init__(self, evaluator):
+        # In __init__ you can do some caching.
+        self._evaluator = evaluator
+
+    def execute(self, default_callback, arguments):
+        return default_callback(arguments)