From 70e125850c595b70215d099ddbeac022204e140e Mon Sep 17 00:00:00 2001
From: Dave T <17680170+davet2001@users.noreply.github.com>
Date: Fri, 22 Apr 2022 06:39:51 +0100
Subject: [PATCH] Limit autogenerated entity_id string length (#69739)

---
 homeassistant/helpers/entity_registry.py | 10 ++++-----
 tests/helpers/test_entity_registry.py    | 28 +++++++++---------------
 2 files changed, 14 insertions(+), 24 deletions(-)

diff --git a/homeassistant/helpers/entity_registry.py b/homeassistant/helpers/entity_registry.py
index af3b0a10559..b4dd0820d8c 100644
--- a/homeassistant/helpers/entity_registry.py
+++ b/homeassistant/helpers/entity_registry.py
@@ -290,7 +290,7 @@ class EntityRegistry:
         if len(domain) > MAX_LENGTH_STATE_DOMAIN:
             raise MaxLengthExceeded(domain, "domain", MAX_LENGTH_STATE_DOMAIN)
 
-        test_string = preferred_string
+        test_string = preferred_string[:MAX_LENGTH_STATE_ENTITY_ID]
         if not known_object_ids:
             known_object_ids = {}
 
@@ -301,11 +301,9 @@ class EntityRegistry:
             or not self.hass.states.async_available(test_string)
         ):
             tries += 1
-            test_string = f"{preferred_string}_{tries}"
-
-        if len(test_string) > MAX_LENGTH_STATE_ENTITY_ID:
-            raise MaxLengthExceeded(
-                test_string, "generated_entity_id", MAX_LENGTH_STATE_ENTITY_ID
+            len_suffix = len(str(tries)) + 1
+            test_string = (
+                f"{preferred_string[:MAX_LENGTH_STATE_ENTITY_ID-len_suffix]}_{tries}"
             )
 
         return test_string
diff --git a/tests/helpers/test_entity_registry.py b/tests/helpers/test_entity_registry.py
index 076e89d64dd..41ac7412d9c 100644
--- a/tests/helpers/test_entity_registry.py
+++ b/tests/helpers/test_entity_registry.py
@@ -1119,22 +1119,13 @@ async def test_disabled_entities_excluded_from_entity_list(hass, registry):
 async def test_entity_max_length_exceeded(hass, registry):
     """Test that an exception is raised when the max character length is exceeded."""
 
-    long_entity_id_name = (
+    long_domain_name = (
         "1234567890123456789012345678901234567890123456789012345678901234567890"
         "1234567890123456789012345678901234567890123456789012345678901234567890"
         "1234567890123456789012345678901234567890123456789012345678901234567890"
         "1234567890123456789012345678901234567890123456789012345678901234567890"
     )
 
-    with pytest.raises(MaxLengthExceeded) as exc_info:
-        registry.async_generate_entity_id("sensor", long_entity_id_name)
-
-    assert exc_info.value.property_name == "generated_entity_id"
-    assert exc_info.value.max_length == 255
-    assert exc_info.value.value == f"sensor.{long_entity_id_name}"
-
-    # Try again but against the domain
-    long_domain_name = long_entity_id_name
     with pytest.raises(MaxLengthExceeded) as exc_info:
         registry.async_generate_entity_id(long_domain_name, "sensor")
 
@@ -1150,14 +1141,15 @@ async def test_entity_max_length_exceeded(hass, registry):
         "1234567890123456789012345678901234567"
     )
 
-    with pytest.raises(MaxLengthExceeded) as exc_info:
-        registry.async_generate_entity_id(
-            "sensor", long_entity_id_name, [f"sensor.{long_entity_id_name}"]
-        )
-
-    assert exc_info.value.property_name == "generated_entity_id"
-    assert exc_info.value.max_length == 255
-    assert exc_info.value.value == f"sensor.{long_entity_id_name}_2"
+    known = []
+    new_id = registry.async_generate_entity_id("sensor", long_entity_id_name, known)
+    assert new_id == "sensor." + long_entity_id_name[: 255 - 7]
+    known.append(new_id)
+    new_id = registry.async_generate_entity_id("sensor", long_entity_id_name, known)
+    assert new_id == "sensor." + long_entity_id_name[: 255 - 7 - 2] + "_2"
+    known.append(new_id)
+    new_id = registry.async_generate_entity_id("sensor", long_entity_id_name, known)
+    assert new_id == "sensor." + long_entity_id_name[: 255 - 7 - 2] + "_3"
 
 
 async def test_resolve_entity_ids(hass, registry):