validation should happen sooner

esphome/core/config.py

@@ -4,8 +4,6 @@ import logging
 import os
 from pathlib import Path
 
-import voluptuous as vol
-
 from esphome import automation, core
 import esphome.codegen as cg
 import esphome.config_validation as cv
@@ -108,60 +106,61 @@ def validate_hostname(config):
     return config
 
 
-def validate_id_hash_collisions(config: dict) -> dict:
-    """Validate that there are no hash collisions between IDs."""
-    area_hashes: dict[int, str] = {}
+def validate_ids_and_references(config: ConfigType) -> ConfigType:
+    """Validate that there are no hash collisions between IDs and that area_id references are valid."""
 
-    # Check main area
+    # Helper to check hash collisions
+    def check_hash_collision(
+        id_obj: core.ID,
+        hash_dict: dict[int, str],
+        item_type: str,
+        path: list[str | int],
+    ) -> bool:
+        if not id_obj.id:
+            return False
+
+        hash_val: int = fnv1a_32bit_hash(id_obj.id)
+        if hash_val in hash_dict and hash_dict[hash_val] != id_obj.id:
+            raise cv.Invalid(
+                f"{item_type} ID '{id_obj.id}' with hash {hash_val} collides with "
+                f"existing {item_type.lower()} ID '{hash_dict[hash_val]}'",
+                path=path,
+            )
+        hash_dict[hash_val] = id_obj.id
+        return True
+
+    # Collect all areas
+    all_areas: list[dict[str, str | core.ID]] = []
     if CONF_AREA in config:
-        area_id: core.ID = config[CONF_AREA][CONF_ID]
-        if area_id.id:
-            area_hash = fnv1a_32bit_hash(area_id.id)
-            area_hashes[area_hash] = area_id.id
+        all_areas.append(config[CONF_AREA])
+    all_areas.extend(config[CONF_AREAS])
 
-    # Check areas list
-    for area in config[CONF_AREAS]:
+    # Validate area hash collisions and collect IDs
+    area_hashes: dict[int, str] = {}
+    area_ids: set[str] = set()
+    for area in all_areas:
         area_id: core.ID = area[CONF_ID]
-        if not area_id.id:
-            continue
+        if check_hash_collision(area_id, area_hashes, "Area", [CONF_AREAS, area_id.id]):
+            area_ids.add(area_id.id)
 
-        area_hash = fnv1a_32bit_hash(area_id.id)
-        if area_hash not in area_hashes:
-            area_hashes[area_hash] = area_id.id
-            continue
-
-        # Skip exact duplicates (handled by IDPassValidationStep)
-        if area_id.id == area_hashes[area_hash]:
-            continue
-
-        raise cv.Invalid(
-            f"Area ID '{area_id.id}' with hash {area_hash} collides with "
-            f"existing area ID '{area_hashes[area_hash]}'",
-            path=[CONF_AREAS, area_id.id],
-        )
-
-    # Check device hash collisions
+    # Validate device hash collisions and area references
     device_hashes: dict[int, str] = {}
-    for device in config[CONF_DEVICES]:
+    for i, device in enumerate(config[CONF_DEVICES]):
         device_id: core.ID = device[CONF_ID]
-        if not device_id.id:
-            continue
-
-        device_hash = fnv1a_32bit_hash(device_id.id)
-        if device_hash not in device_hashes:
-            device_hashes[device_hash] = device_id.id
-            continue
-
-        # Skip exact duplicates (handled by IDPassValidationStep)
-        if device_id.id == device_hashes[device_hash]:
-            continue
-
-        raise cv.Invalid(
-            f"Device ID '{device_id.id}' with hash {device_hash} collides "
-            f"with existing device ID '{device_hashes[device_hash]}'",
-            path=[CONF_DEVICES, device_id.id],
+        check_hash_collision(
+            device_id, device_hashes, "Device", [CONF_DEVICES, device_id.id]
         )
 
+        # Validate area_id reference if present
+        if CONF_AREA_ID in device:
+            area_ref_id: core.ID = device[CONF_AREA_ID]
+            if area_ref_id.id not in area_ids:
+                raise cv.Invalid(
+                    f"Device '{device[CONF_NAME]}' has an area_id '{area_ref_id.id}'"
+                    " that does not exist.",
+                    path=[CONF_DEVICES, i, CONF_AREA_ID],
+                )
+
     return config
 
 
@@ -289,7 +288,7 @@ CONFIG_SCHEMA = cv.All(
         }
     ),
     validate_hostname,
-    validate_id_hash_collisions,
+    validate_ids_and_references,
 )
 
 PRELOAD_CONFIG_SCHEMA = cv.Schema(
@@ -537,44 +536,25 @@ async def to_code(config: ConfigType) -> None:
     if config[CONF_PLATFORMIO_OPTIONS]:
         CORE.add_job(_add_platformio_options, config[CONF_PLATFORMIO_OPTIONS])
 
-    # Helper function to process an area configuration
-    def process_area(
-        area_conf: dict[str, str | core.ID],
-        area_ids: set[str],
-    ) -> None:
-        """Process and register an area configuration."""
-        area_id: core.ID = area_conf[CONF_ID]
-        area_id_str: str = area_id.id
-        area_id_hash = fnv1a_32bit_hash(area_id_str)
-        area_name: str = area_conf[CONF_NAME]
-
-        area_ids.add(area_id_str)
-
-        area_var = cg.new_Pvariable(area_id)
-        cg.add(area_var.set_area_id(area_id_hash))
-        cg.add(area_var.set_name(area_name))
-        cg.add(cg.App.register_area(area_var))
-
-    # Initialize tracking structures
-    area_ids: set[str] = set()
-
-    # Collect all areas to process
+    # Process areas
     all_areas: list[dict[str, str | core.ID]] = []
-
-    # Add top-level area if present
-    if area_conf := config.get(CONF_AREA):
-        all_areas.append(area_conf)
-
-    # Add areas from CONF_AREAS list
+    if CONF_AREA in config:
+        all_areas.append(config[CONF_AREA])
     all_areas.extend(config[CONF_AREAS])
 
-    # Reserve space for areas and process them
     if all_areas:
         cg.add(cg.RawStatement(f"App.reserve_area({len(all_areas)});"))
         cg.add_define("USE_AREAS")
 
         for area_conf in all_areas:
-            process_area(area_conf, area_ids)
+            area_id: core.ID = area_conf[CONF_ID]
+            area_id_hash: int = fnv1a_32bit_hash(area_id.id)
+            area_name: str = area_conf[CONF_NAME]
+
+            area_var = cg.new_Pvariable(area_id)
+            cg.add(area_var.set_area_id(area_id_hash))
+            cg.add(area_var.set_name(area_name))
+            cg.add(cg.App.register_area(area_var))
 
     # Process devices
     devices: list[dict[str, str | core.ID]] = config[CONF_DEVICES]
@@ -598,12 +578,6 @@ async def to_code(config: ConfigType) -> None:
         # Set area if specified
         if CONF_AREA_ID in dev_conf:
             area_id: core.ID = dev_conf[CONF_AREA_ID]
-            if area_id.id not in area_ids:
-                raise vol.Invalid(
-                    f"Device '{device_name}' has an area_id '{area_id.id}'"
-                    " that does not exist.",
-                    path=[CONF_DEVICES, dev_conf[CONF_ID], CONF_AREA_ID],
-                )
             area_id_hash = fnv1a_32bit_hash(area_id.id)
             cg.add(dev.set_area_id(area_id_hash))
 

tests/unit_tests/core/test_config.py

@@ -205,7 +205,10 @@ def test_device_with_invalid_area_id(
 
     # Check for the specific error message in stdout
     captured = capsys.readouterr()
-    assert "Couldn't find ID 'nonexistent_area'" in captured.out
+    assert (
+        "Device 'Test Device' has an area_id 'nonexistent_area' that does not exist."
+        in captured.out
+    )
 
 
 def test_device_id_hash_collision(