Enable auto-discovery of plugins

Fixes ethereum#1230

trinity/main.py

@@ -51,7 +51,7 @@
     SharedProcessScope,
 )
 from trinity.plugins.registry import (
-    ENABLED_PLUGINS
+    ALL_PLUGINS,
 )
 from trinity.utils.ipc import (
     wait_for_ipc,
@@ -377,6 +377,6 @@ async def handle_networking_exit(service: BaseService,
 def setup_plugins(scope: BaseManagerProcessScope) -> PluginManager:
     plugin_manager = PluginManager(scope)
     # TODO: Implement auto-discovery of plugins based on some convention/configuration scheme
-    plugin_manager.register(ENABLED_PLUGINS)
+    plugin_manager.register(ALL_PLUGINS)
 
     return plugin_manager

trinity/plugins/registry.py

@@ -33,11 +33,19 @@ def is_ipython_available() -> bool:
 # we'll be able to load plugins from some path and control via Trinity
 # config file which plugin is enabled or not
 
-ENABLED_PLUGINS = [
+BUILTIN_PLUGINS = [
     AttachPlugin() if is_ipython_available() else AttachPlugin(use_ipython=False),
     EthstatsPlugin(),
     FixUncleanShutdownPlugin(),
     JsonRpcServerPlugin(),
     LightPeerChainBridgePlugin(),
     TxPlugin(),
 ]
+
+# Plugins need to define entrypoints at 'trinity.plugins' to automatically get loaded
+# https://packaging.python.org/guides/creating-and-discovering-plugins/#using-package-metadata
+DISCOVERED_PLUGINS = [
+    entry_point.load()() for entry_point in pkg_resources.iter_entry_points('trinity.plugins')
+]
+
+ALL_PLUGINS = BUILTIN_PLUGINS + DISCOVERED_PLUGINS