Allow panels with external URL (#9214)

* Allow panels with external URL

* Update comment

homeassistant/components/frontend/__init__.py

@@ -109,14 +109,13 @@ def register_panel(hass, component_name, path, md5=None, sidebar_title=None,
 
     component_name: name of the web component
     path: path to the HTML of the web component
+          (required unless url is provided)
     md5: the md5 hash of the web component (for versioning, optional)
     sidebar_title: title to show in the sidebar (optional)
     sidebar_icon: icon to show next to title in sidebar (optional)
     url_path: name to use in the url (defaults to component_name)
-    url: for the web component (for dev environment, optional)
+    url: for the web component (optional)
     config: config to be passed into the web component
-
-    Warning: this API will probably change. Use at own risk.
     """
     panels = hass.data.get(DATA_PANELS)
     if panels is None:
@@ -127,14 +126,16 @@ def register_panel(hass, component_name, path, md5=None, sidebar_title=None,
 
     if url_path in panels:
         _LOGGER.warning("Overwriting component %s", url_path)
-    if not os.path.isfile(path):
-        _LOGGER.error(
-            "Panel %s component does not exist: %s", component_name, path)
-        return
 
-    if md5 is None:
-        with open(path) as fil:
-            md5 = hashlib.md5(fil.read().encode('utf-8')).hexdigest()
+    if url is None:
+        if not os.path.isfile(path):
+            _LOGGER.error(
+                "Panel %s component does not exist: %s", component_name, path)
+            return
+
+        if md5 is None:
+            with open(path) as fil:
+                md5 = hashlib.md5(fil.read().encode('utf-8')).hexdigest()
 
     data = {
         'url_path': url_path,

tests/components/test_frontend.py

@@ -7,7 +7,7 @@ import pytest
 
 from homeassistant.setup import async_setup_component
 from homeassistant.components.frontend import (
-    DOMAIN, ATTR_THEMES, ATTR_EXTRA_HTML_URL)
+    DOMAIN, ATTR_THEMES, ATTR_EXTRA_HTML_URL, DATA_PANELS, register_panel)
 
 
 @pytest.fixture
@@ -163,3 +163,20 @@ def test_extra_urls(mock_http_client_with_urls):
     assert resp.status == 200
     text = yield from resp.text()
     assert text.find('href=\'https://domain.com/my_extra_url.html\'') >= 0
+
+
+@asyncio.coroutine
+def test_panel_without_path(hass):
+    """Test panel registration without file path."""
+    register_panel(hass, 'test_component', 'nonexistant_file')
+    assert hass.data[DATA_PANELS] == {}
+
+
+@asyncio.coroutine
+def test_panel_with_url(hass):
+    """Test panel registration without file path."""
+    register_panel(hass, 'test_component', None, url='some_url')
+    assert hass.data[DATA_PANELS] == {
+        'test_component': {'component_name': 'test_component',
+                           'url': 'some_url',
+                           'url_path': 'test_component'}}