Add support for an external step in config flow (#23782)

* Add support for an external step in config flow

* Types

* Lint

tests/common.py

@@ -951,3 +951,16 @@ def mock_entity_platform(hass, platform_path, module):
 
     _LOGGER.info("Adding mock integration platform: %s", platform_path)
     module_cache["{}.{}".format(platform_name, domain)] = module
+
+
+def async_capture_events(hass, event_name):
+    """Create a helper that captures events."""
+    events = []
+
+    @ha.callback
+    def capture_events(event):
+        events.append(event)
+
+    hass.bus.async_listen(event_name, capture_events)
+
+    return events

tests/test_data_entry_flow.py

@@ -5,6 +5,8 @@ import voluptuous as vol
 from homeassistant import data_entry_flow
 from homeassistant.util.decorator import Registry
 
+from tests.common import async_capture_events
+
 
 @pytest.fixture
 def manager():
@@ -245,3 +247,57 @@ async def test_finish_callback_change_result_type(hass):
     result = await manager.async_configure(result['flow_id'], {'count': 2})
     assert result['type'] == data_entry_flow.RESULT_TYPE_CREATE_ENTRY
     assert result['result'] == 2
+
+
+async def test_external_step(hass, manager):
+    """Test external step logic."""
+    manager.hass = hass
+
+    @manager.mock_reg_handler('test')
+    class TestFlow(data_entry_flow.FlowHandler):
+        VERSION = 5
+        data = None
+
+        async def async_step_init(self, user_input=None):
+            if not user_input:
+                return self.async_external_step(
+                    step_id='init',
+                    url='https://example.com',
+                )
+
+            self.data = user_input
+            return self.async_external_step_done(next_step_id='finish')
+
+        async def async_step_finish(self, user_input=None):
+            return self.async_create_entry(
+                title=self.data['title'],
+                data=self.data
+            )
+
+    events = async_capture_events(
+        hass, data_entry_flow.EVENT_DATA_ENTRY_FLOW_PROGRESSED
+    )
+
+    result = await manager.async_init('test')
+    assert result['type'] == data_entry_flow.RESULT_TYPE_EXTERNAL_STEP
+    assert len(manager.async_progress()) == 1
+
+    # Mimic external step
+    # Called by integrations: `hass.config_entries.flow.async_configure(…)`
+    result = await manager.async_configure(result['flow_id'], {
+        'title': 'Hello'
+    })
+    assert result['type'] == data_entry_flow.RESULT_TYPE_EXTERNAL_STEP_DONE
+
+    await hass.async_block_till_done()
+    assert len(events) == 1
+    assert events[0].data == {
+        'handler': 'test',
+        'flow_id': result['flow_id'],
+        'refresh': True
+    }
+
+    # Frontend refreshses the flow
+    result = await manager.async_configure(result['flow_id'])
+    assert result['type'] == data_entry_flow.RESULT_TYPE_CREATE_ENTRY
+    assert result['title'] == "Hello"