Move example plugin and reuse it for integration test

This moves the example plugin out of Trinity itself.
We also use this external plugin for the integration
test now.
This ensures we are testing the discovery mechanism
under realistic conditions.

Author: cburgdorf

docs/guides/trinity/writing_plugins.rst

@@ -174,7 +174,7 @@ which is the most commonly used plugin category.
 
 Every plugin needs to overwrite ``name`` so voilà, here's our first plugin!
 
-.. literalinclude:: ../../../trinity/plugins/examples/peer_count_reporter/plugin.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/peer_count_reporter_plugin/plugin.py
    :language: python
    :pyobject: PeerCountReporterPlugin
    :end-before: def configure_parser
@@ -196,7 +196,7 @@ command line arguments in many different ways.
 
 For example, here we are adding a boolean flag ``--report-peer-count`` to Trinity.
 
-.. literalinclude:: ../../../trinity/plugins/examples/peer_count_reporter/plugin.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/peer_count_reporter_plugin/plugin.py
    :language: python
    :pyobject: PeerCountReporterPlugin.configure_parser
 
@@ -236,14 +236,14 @@ While it is absolutely possible to put this logic right into the plugin, the pre
 subclass :class:`~p2p.service.BaseService` and implement the core logic in such a standalone
 service.
 
-.. literalinclude:: ../../../trinity/plugins/examples/peer_count_reporter/plugin.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/peer_count_reporter_plugin/plugin.py
    :language: python
    :pyobject: PeerCountReporter
 
 Then, the implementation of :meth:`~trinity.extensibility.plugin.BaseIsolatedPlugin.do_start` is
 only concerned about running the service on a fresh event loop.
 
-.. literalinclude:: ../../../trinity/plugins/examples/peer_count_reporter/plugin.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/peer_count_reporter_plugin/plugin.py
    :language: python
    :pyobject: PeerCountReporterPlugin.do_start
 
@@ -270,7 +270,7 @@ Hence, to actually start a plugin, the plugin needs to invoke the
 ``READY`` state. Let's assume a simple case in which we simply want to start the plugin if Trinity
 is started with the ``--report-peer-count`` flag.
 
-.. literalinclude:: ../../../trinity/plugins/examples/peer_count_reporter/plugin.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/peer_count_reporter_plugin/plugin.py
    :language: python
    :pyobject: PeerCountReporterPlugin.on_ready
 
@@ -325,11 +325,11 @@ In this guide, we won't go into details about how to create Python packages as t
 Once we have a ``setup.py`` file, all we have to do is to expose our plugin under
 ``trinity.plugins`` via the ``entry_points`` section.
 
-.. literalinclude:: ../../../tests/trinity/integration/trinity_test_plugin/setup.py
+.. literalinclude:: ../../../trinity-external-plugins/examples/peer_count_reporter/setup.py
    :language: python
 
 Check out the `official documentation on entry points <https://packaging.python.org/guides/creating-and-discovering-plugins/#using-package-metadata>`_
 for a deeper explanation.
 
 A plugin where the ``setup.py`` file is configured as described can be installed by
-``pip install <package-name>``` and is immediately available as a plugin in Trinity.
+``pip install <package-name>``` and immediately becomes available as a plugin in Trinity.

tests/trinity/integration/test_plugin_discovery.py

@@ -1,4 +1,12 @@
+from trinity.plugins.registry import (
+    get_all_plugins
+)
+# This plugin is external to this code base and installed by tox
+# In order to install it locally run:
+# pip install -e trinity-external-plugins/examples/peer_count_reporter
+from peer_count_reporter_plugin import PeerCountReporterPlugin
+
+
 def test_plugin_discovery():
-    from trinity_test_plugin import TestPlugin
-    from trinity.plugins.registry import ALL_PLUGINS
-    assert any(isinstance(plugin, TestPlugin) for plugin in ALL_PLUGINS)
+    plugins = [type(plugin) for plugin in get_all_plugins()]
+    assert PeerCountReporterPlugin in plugins

tests/trinity/integration/trinity_test_plugin/__init__.py

@@ -66,11 +66,11 @@ commands=
 
 [common-trinity-integration]
 deps = .[p2p,trinity,eth-extra,test]
-        {toxinidir}/tests/trinity/integration/trinity_test_plugin/dist/trinity_test_plugin-0.0.0.tar.gz
 passenv =
     PYTEST_ADDOPTS
     TRAVIS_EVENT_TYPE
 commands=
+    pip install -e {toxinidir}/trinity-external-plugins/examples/peer_count_reporter
     # We don't want to run these tests concurrently to avoid running into errors
     # due to multiple Trinity instances competing for the same ports
     pytest -n 1 {posargs:tests/trinity/integration/ -k 'not lightchain_integration'}

tests/trinity/integration/trinity_test_plugin/dist/trinity_test_plugin-0.0.0.tar.gz

@@ -0,0 +1,11 @@
+# External Plugins
+
+This directory is for plugins that do not come bundled with Trinity itself and hence need to be installed through pip.
+
+## Installing plugins from PyPi
+
+Run: `pip install <plugin-pypi-name>
+
+## Installing plugins from local directory
+
+Run `pip install /path/to/plugin`

tests/trinity/integration/trinity_test_plugin/setup.py

@@ -0,0 +1 @@
+from .plugin import PeerCountReporterPlugin