[core] Fix area/device hash collision validation not running (#15259)

esphome/config.py

@@ -958,6 +958,23 @@ class FinalValidateValidationStep(ConfigValidationStep):
         fv.full_config.reset(token)
 
 
+class CoreFinalValidateStep(ConfigValidationStep):
+    """Run final validation on core esphome config (area/device hash collisions)."""
+
+    # Same priority as component final validate steps
+    priority = -20.0
+
+    def run(self, result: Config) -> None:
+        if result.errors:
+            return
+
+        token = fv.full_config.set(result)
+        with result.catch_error([CONF_ESPHOME]):
+            if CONF_ESPHOME in result:
+                core_config.validate_ids_and_references(result[CONF_ESPHOME])
+        fv.full_config.reset(token)
+
+
 class PinUseValidationCheck(ConfigValidationStep):
     """Check for pin reuse"""
 
@@ -1085,6 +1102,7 @@ def validate_config(
     for domain, conf in config.items():
         result.add_validation_step(LoadValidationStep(domain, conf))
     result.add_validation_step(IDPassValidationStep())
+    result.add_validation_step(CoreFinalValidateStep())
     result.add_validation_step(PinUseValidationCheck())
 
     result.add_validation_step(RemoveReferenceValidationStep())

esphome/core/config.py

@@ -156,22 +156,22 @@ def validate_ids_and_references(config: ConfigType) -> ConfigType:
         hash_dict[hash_val] = id_obj.id
 
     # Collect all areas
-    all_areas: list[dict[str, str | core.ID]] = []
+    all_areas: list[tuple[dict[str, str | core.ID], str]] = []
     if CONF_AREA in config:
-        all_areas.append(config[CONF_AREA])
-    all_areas.extend(config[CONF_AREAS])
+        all_areas.append((config[CONF_AREA], CONF_AREA))
+    all_areas.extend((area, CONF_AREAS) for area in config.get(CONF_AREAS, []))
 
     # Validate area hash collisions and collect IDs
     area_hashes: dict[int, str] = {}
     area_ids: set[str] = set()
-    for area in all_areas:
+    for area, key in all_areas:
         area_id: core.ID = area[CONF_ID]
-        check_hash_collision(area_id, area_hashes, "Area", [CONF_AREAS, area_id.id])
+        check_hash_collision(area_id, area_hashes, "Area", [key, area_id.id])
         area_ids.add(area_id.id)
 
     # Validate device hash collisions and area references
     device_hashes: dict[int, str] = {}
-    for device in config[CONF_DEVICES]:
+    for device in config.get(CONF_DEVICES, []):
         device_id: core.ID = device[CONF_ID]
         check_hash_collision(
             device_id, device_hashes, "Device", [CONF_DEVICES, device_id.id]
@@ -329,9 +329,6 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-FINAL_VALIDATE_SCHEMA = cv.All(validate_ids_and_references)
-
-
 PRELOAD_CONFIG_SCHEMA = cv.Schema(
     {
         cv.Required(CONF_NAME): cv.valid_name,