Always use shared zeroconf in cast config flow (#42210)

homeassistant/components/cast/config_flow.py

@@ -4,6 +4,7 @@ import functools
 from pychromecast.discovery import discover_chromecasts, stop_discovery
 
 from homeassistant import config_entries
+from homeassistant.components import zeroconf
 from homeassistant.helpers import config_entry_flow
 
 from .const import DOMAIN
@@ -11,12 +12,19 @@ from .helpers import ChromeCastZeroconf
 
 
 async def _async_has_devices(hass):
-    """Return if there are devices that can be discovered."""
+    """
+    Return if there are devices that can be discovered.
+
+    This function will be called if no devices are already found through the zeroconf
+    integration.
+    """
+
+    zeroconf_instance = ChromeCastZeroconf.get_zeroconf()
+    if zeroconf_instance is None:
+        zeroconf_instance = await zeroconf.async_get_instance(hass)
 
     casts, browser = await hass.async_add_executor_job(
-        functools.partial(
-            discover_chromecasts, zeroconf_instance=ChromeCastZeroconf.get_zeroconf()
-        )
+        functools.partial(discover_chromecasts, zeroconf_instance=zeroconf_instance)
     )
     stop_discovery(browser)
     return casts