Don't initialize components which have already been discovered (#6381)

* Don't initialize components which have already been discovered (fixes #5588)

* Don't log that we've found a service unless we know it's not a duplicate

* Encode discovery data hash with JSON

This also solves the issue of trying to hash non-hashable objects like dicts

* Add test for duplicate device discovery

homeassistant/components/discovery.py

@@ -7,6 +7,7 @@ Knows which components handle certain types, will make sure they are
 loaded before the EVENT_PLATFORM_DISCOVERED is fired.
 """
 import asyncio
+import json
 from datetime import timedelta
 import logging
 
@@ -65,6 +66,7 @@ def async_setup(hass, config):
 
     logger = logging.getLogger(__name__)
     netdisco = NetworkDiscovery()
+    already_discovered = set()
 
     # Disable zeroconf logging, it spams
     logging.getLogger('zeroconf').setLevel(logging.CRITICAL)
@@ -79,14 +81,20 @@ def async_setup(hass, config):
             logger.info("Ignoring service: %s %s", service, info)
             return
 
-        logger.info("Found new service: %s %s", service, info)
-
         comp_plat = SERVICE_HANDLERS.get(service)
 
         # We do not know how to handle this service.
         if not comp_plat:
             return
 
+        discovery_hash = json.dumps([service, info], sort_keys=True)
+        if discovery_hash in already_discovered:
+            return
+
+        already_discovered.add(discovery_hash)
+
+        logger.info("Found new service: %s %s", service, info)
+
         component, platform = comp_plat
 
         if platform is None:

tests/components/test_discovery.py

@@ -126,3 +126,30 @@ def test_ignore_service(hass):
 
     assert not mock_discover.called
     assert not mock_platform.called
+
+
+@asyncio.coroutine
+def test_discover_duplicates(hass):
+    """Test load a component."""
+    result = yield from async_setup_component(hass, 'discovery', BASE_CONFIG)
+    assert result
+
+    def discover(netdisco):
+        """Fake discovery."""
+        return [(SERVICE_NO_PLATFORM, SERVICE_INFO),
+                (SERVICE_NO_PLATFORM, SERVICE_INFO)]
+
+    with patch.object(discovery, '_discover', discover), \
+            patch('homeassistant.components.discovery.async_discover',
+                  return_value=mock_coro()) as mock_discover, \
+            patch('homeassistant.components.discovery.async_load_platform',
+                  return_value=mock_coro()) as mock_platform:
+        hass.bus.async_fire(EVENT_HOMEASSISTANT_START)
+        yield from hass.async_block_till_done()
+
+    assert mock_discover.called
+    assert mock_discover.call_count == 1
+    assert not mock_platform.called
+    mock_discover.assert_called_with(
+        hass, SERVICE_NO_PLATFORM, SERVICE_INFO,
+        SERVICE_NO_PLATFORM_COMPONENT, BASE_CONFIG)