[wifi] Accept boolean-like strings for fast_connect again

esphome/components/wifi/__init__.py

@@ -1,5 +1,6 @@
 import logging
 import math
+from typing import Any
 
 from esphome import automation, preferences
 from esphome.automation import Condition
@@ -444,9 +445,10 @@ FAST_CONNECT_SCHEMA = cv.Schema(
 )
 
 
-def _fast_connect_schema(value):
+def _fast_connect_schema(value: Any) -> ConfigType:
-    """Accept the historic plain boolean or a dict with enabled/storage keys."""
+    """Accept the historic plain boolean (including boolean-like strings from
-    if isinstance(value, bool):
+    substitutions) or a dict with enabled/storage keys."""
+    if not isinstance(value, dict):
         value = {CONF_ENABLED: value}
     return FAST_CONNECT_SCHEMA(value)
 

tests/components/wifi/validate-fast-connect-substitution.esp8266-ard.yaml

@@ -0,0 +1,9 @@
+# fast_connect passed through a substitution arrives as a string ("false"),
+# which must be accepted like the historic plain boolean form.
+substitutions:
+  fast_connect_value: "false"
+
+wifi:
+  ssid: MySSID
+  password: password1
+  fast_connect: ${fast_connect_value}