bus: Allow overriding discover search path

Change-Id: I0fb9ce0f6166fea48dec18b295319c6d4e001567

charms_openstack/bus.py

@@ -21,7 +21,7 @@ import charmhelpers.core.hookenv as hookenv
 # Code below is based on charms.reactive.bus
 
 
-def discover():
+def discover(search_path=None):
     """Discover Openstack handlers based on convention.
 
     Handlers will be loaded from the following directory and its
@@ -30,10 +30,14 @@ def discover():
       * ``$CHARM_DIR/lib/charm/openstack``
 
     The Python files will be imported and decorated functions registered.
+
+    :param search_path: Override path to search for handlers.
+    :type search_path: Optional[str]
     """
-    search_path = os.path.join(
-        hookenv.charm_dir(), 'lib', 'charm', 'openstack')
-    base_path = os.path.join(hookenv.charm_dir(), 'lib', 'charm')
+    if not search_path:
+        search_path = os.path.join(
+            hookenv.charm_dir(), 'lib', 'charm', 'openstack')
+    base_path = os.path.dirname(search_path)
     for dirpath, dirnames, filenames in os.walk(search_path):
         for filename in filenames:
             filepath = os.path.join(dirpath, filename)

unit_tests/test_charms_openstack_bus.py

@@ -44,6 +44,26 @@ class TestBus(unittest.TestCase):
                 '/x/unit-aodh-1/charm/lib/charm/openstack/aodh.py')]
         _register_handlers_from_file.assert_has_calls(expect_calls)
 
+    @mock.patch.object(bus.os, 'walk')
+    @mock.patch.object(bus, '_register_handlers_from_file')
+    @mock.patch('charmhelpers.core.hookenv.charm_dir')
+    def test_discover_search_path(self, charm_dir,
+                                  _register_handlers_from_file, walk):
+        os.walk.return_value = [(
+            '/x/unit-aodh-1/charm/lib/charms',
+            ['__pycache__'],
+            ['__init__.py', 'aodh.py'])]
+
+        bus.discover(search_path='/x/unit-aodh-1/charm/lib/charms')
+        expect_calls = [
+            mock.call(
+                '/x/unit-aodh-1/charm/lib',
+                '/x/unit-aodh-1/charm/lib/charms/__init__.py'),
+            mock.call(
+                '/x/unit-aodh-1/charm/lib',
+                '/x/unit-aodh-1/charm/lib/charms/aodh.py')]
+        _register_handlers_from_file.assert_has_calls(expect_calls)
+
     @mock.patch.object(bus.importlib, 'import_module')
     def test_load_module(self, import_module):
         import_module.side_effect = lambda x: x