[core] Remove object_id RAM storage - no longer in hot path after #12627

esphome/core/entity_base.cpp

@@ -9,7 +9,8 @@ static const char *const TAG = "entity_base";
 
 // Entity Name
 const StringRef &EntityBase::get_name() const { return this->name_; }
-void EntityBase::set_name(const char *name) {
+void EntityBase::set_name(const char *name) { this->set_name(name, 0); }
+void EntityBase::set_name(const char *name, uint32_t object_id_hash) {
   this->name_ = StringRef(name);
   if (this->name_.empty()) {
 #ifdef USE_DEVICES
@@ -21,8 +22,16 @@ void EntityBase::set_name(const char *name) {
       this->name_ = StringRef(App.get_friendly_name());
     }
     this->flags_.has_own_name = false;
+    // Dynamic name - must calculate hash at runtime
+    this->calc_object_id_();
   } else {
     this->flags_.has_own_name = true;
+    // Static name - use pre-computed hash if provided
+    if (object_id_hash != 0) {
+      this->object_id_hash_ = object_id_hash;
+    } else {
+      this->calc_object_id_();
+    }
   }
 }
 
@@ -45,69 +54,34 @@ void EntityBase::set_icon(const char *icon) {
 #endif
 }
 
-// Check if the object_id is dynamic (changes with MAC suffix)
-bool EntityBase::is_object_id_dynamic_() const {
-  return !this->flags_.has_own_name && App.is_name_add_mac_suffix_enabled();
-}
-
-// Entity Object ID
+// Entity Object ID - computed on-demand from name
 std::string EntityBase::get_object_id() const {
-  // Check if `App.get_friendly_name()` is constant or dynamic.
-  if (this->is_object_id_dynamic_()) {
-    // `App.get_friendly_name()` is dynamic.
-    return str_sanitize(str_snake_case(App.get_friendly_name()));
-  }
-  // `App.get_friendly_name()` is constant.
-  return this->object_id_c_str_ == nullptr ? "" : this->object_id_c_str_;
-}
-void EntityBase::set_object_id(const char *object_id) {
-  this->object_id_c_str_ = object_id;
-  this->calc_object_id_();
-}
-
-void EntityBase::set_name_and_object_id(const char *name, const char *object_id) {
-  this->set_name(name);
-  this->object_id_c_str_ = object_id;
-  this->calc_object_id_();
-}
-
-// Calculate Object ID Hash from Entity Name
-void EntityBase::calc_object_id_() {
   char buf[OBJECT_ID_MAX_LEN];
-  StringRef object_id = this->get_object_id_to(buf);
-  this->object_id_hash_ = fnv1_hash(object_id.c_str());
+  size_t len = this->write_object_id_to(buf, sizeof(buf));
+  return std::string(buf, len);
 }
 
-// Format dynamic object_id: sanitized snake_case of friendly_name
-static size_t format_dynamic_object_id(char *buf, size_t buf_size) {
-  const std::string &name = App.get_friendly_name();
-  size_t len = std::min(name.size(), buf_size - 1);
-  for (size_t i = 0; i < len; i++) {
-    buf[i] = to_sanitized_char(to_snake_case_char(name[i]));
-  }
-  buf[len] = '\0';
-  return len;
+// Calculate Object ID Hash directly from name using snake_case + sanitize
+void EntityBase::calc_object_id_() {
+  this->object_id_hash_ = fnv1_hash_object_id(this->name_.c_str(), this->name_.size());
 }
 
 size_t EntityBase::write_object_id_to(char *buf, size_t buf_size) const {
-  if (this->is_object_id_dynamic_()) {
-    return format_dynamic_object_id(buf, buf_size);
+  size_t len = std::min(this->name_.size(), buf_size - 1);
+  for (size_t i = 0; i < len; i++) {
+    buf[i] = to_sanitized_char(to_snake_case_char(this->name_[i]));
   }
-  const char *src = this->object_id_c_str_ == nullptr ? "" : this->object_id_c_str_;
-  size_t len = strlen(src);
-  if (len >= buf_size)
-    len = buf_size - 1;
-  memcpy(buf, src, len);
   buf[len] = '\0';
   return len;
 }
 
 StringRef EntityBase::get_object_id_to(std::span<char, OBJECT_ID_MAX_LEN> buf) const {
-  if (this->is_object_id_dynamic_()) {
-    size_t len = format_dynamic_object_id(buf.data(), buf.size());
-    return StringRef(buf.data(), len);
+  size_t len = std::min(this->name_.size(), buf.size() - 1);
+  for (size_t i = 0; i < len; i++) {
+    buf[i] = to_sanitized_char(to_snake_case_char(this->name_[i]));
   }
-  return this->object_id_c_str_ == nullptr ? StringRef() : StringRef(this->object_id_c_str_);
+  buf[len] = '\0';
+  return StringRef(buf.data(), len);
 }
 
 uint32_t EntityBase::get_object_id_hash() { return this->object_id_hash_; }

esphome/core/entity_base.h

@@ -28,6 +28,9 @@ class EntityBase {
   // Get/set the name of this Entity
   const StringRef &get_name() const;
   void set_name(const char *name);
+  /// Set name with pre-computed object_id hash (avoids runtime hash calculation)
+  /// Use hash=0 for dynamic names that need runtime calculation
+  void set_name(const char *name, uint32_t object_id_hash);
 
   // Get whether this Entity has its own name or it should use the device friendly_name.
   bool has_own_name() const { return this->flags_.has_own_name; }
@@ -43,10 +46,6 @@ class EntityBase {
                 "which will remain available longer. get_object_id() will be removed in 2026.7.0",
                 "2025.12.0")
   std::string get_object_id() const;
-  void set_object_id(const char *object_id);
-
-  // Set both name and object_id in one call (reduces generated code size)
-  void set_name_and_object_id(const char *name, const char *object_id);
 
   // Get the unique Object ID of this Entity
   uint32_t get_object_id_hash();
@@ -140,11 +139,7 @@ class EntityBase {
  protected:
   void calc_object_id_();
 
-  /// Check if the object_id is dynamic (changes with MAC suffix)
-  bool is_object_id_dynamic_() const;
-
   StringRef name_;
-  const char *object_id_c_str_{nullptr};
 #ifdef USE_ENTITY_ICON
   const char *icon_c_str_{nullptr};
 #endif

esphome/core/entity_helpers.py

@@ -15,7 +15,7 @@ from esphome.const import (
 from esphome.core import CORE, ID
 from esphome.cpp_generator import MockObj, add, get_variable
 import esphome.final_validate as fv
-from esphome.helpers import sanitize, snake_case
+from esphome.helpers import fnv1_hash_object_id, sanitize, snake_case
 from esphome.types import ConfigType, EntityMetadata
 
 _LOGGER = logging.getLogger(__name__)
@@ -75,34 +75,21 @@ async def setup_entity(var: MockObj, config: ConfigType, platform: str) -> None:
         config: Configuration dictionary containing entity settings
         platform: The platform name (e.g., "sensor", "binary_sensor")
     """
-    # Get device info
-    device_name: str | None = None
+    # Set device if configured
     device_id_obj: ID | None
     if device_id_obj := config.get(CONF_DEVICE_ID):
         device: MockObj = await get_variable(device_id_obj)
         add(var.set_device(device))
-        # Get device name for object ID calculation
-        device_name = device_id_obj.id
 
-    # Calculate base object_id using the same logic as C++
-    # This must match the C++ behavior in esphome/core/entity_base.cpp
-    base_object_id = get_base_entity_object_id(
-        config[CONF_NAME], CORE.friendly_name, device_name
-    )
-
-    if not config[CONF_NAME]:
-        _LOGGER.debug(
-            "Entity has empty name, using '%s' as object_id base", base_object_id
-        )
-
-    # Set both name and object_id in one call to reduce generated code size
-    add(var.set_name_and_object_id(config[CONF_NAME], base_object_id))
-    _LOGGER.debug(
-        "Setting object_id '%s' for entity '%s' on platform '%s'",
-        base_object_id,
-        config[CONF_NAME],
-        platform,
-    )
+    # Set the entity name with pre-computed object_id hash
+    # For entities with a name, we pre-compute the hash to avoid runtime calculation
+    # For empty names (use device friendly_name), pass 0 to compute at runtime
+    entity_name = config[CONF_NAME]
+    if entity_name:
+        object_id_hash = fnv1_hash_object_id(entity_name)
+        add(var.set_name(entity_name, object_id_hash))
+    else:
+        add(var.set_name(entity_name, 0))
     # Only set disabled_by_default if True (default is False)
     if config[CONF_DISABLED_BY_DEFAULT]:
         add(var.set_disabled_by_default(True))

esphome/core/helpers.h

@@ -529,6 +529,20 @@ constexpr char to_sanitized_char(char c) {
 /// Sanitizes the input string by removing all characters but alphanumerics, dashes and underscores.
 std::string str_sanitize(const std::string &str);
 
+/// Calculate FNV-1 hash of a string while applying snake_case + sanitize transformations.
+/// This computes object_id hashes directly from names without creating an intermediate buffer.
+/// IMPORTANT: Must match Python fnv1_hash_object_id() in esphome/helpers.py.
+/// If you modify this function, update the Python version and tests in both places.
+inline uint32_t fnv1_hash_object_id(const char *str, size_t len) {
+  uint32_t hash = FNV1_OFFSET_BASIS;
+  for (size_t i = 0; i < len; i++) {
+    hash *= FNV1_PRIME;
+    // Apply snake_case (space->underscore, uppercase->lowercase) then sanitize
+    hash ^= static_cast<uint8_t>(to_sanitized_char(to_snake_case_char(str[i])));
+  }
+  return hash;
+}
+
 /// snprintf-like function returning std::string of maximum length \p len (excluding null terminator).
 std::string __attribute__((format(printf, 1, 3))) str_snprintf(const char *fmt, size_t len, ...);
 

esphome/helpers.py

@@ -70,6 +70,34 @@ def fnv1a_32bit_hash(string: str) -> int:
     return hash_value
 
 
+def fnv1_hash_object_id(name: str) -> int:
+    """Compute FNV-1 hash of name with snake_case + sanitize transformations.
+
+    IMPORTANT: This must match the C++ fnv1_hash_object_id() in esphome/core/helpers.h.
+    If you modify this function, update the C++ version and tests in both places.
+
+    Used for pre-computing entity object_id hashes at code generation time.
+    """
+    hash_value = 2166136261  # FNV1_OFFSET_BASIS
+    for char in name:
+        # Apply snake_case: space -> underscore, uppercase -> lowercase
+        if char == " ":
+            c = "_"
+        elif "A" <= char <= "Z":
+            c = chr(ord(char) + 32)  # lowercase
+        else:
+            c = char
+        # Apply sanitize: keep alphanumerics, dash, underscore; replace others with _
+        if not (
+            c in {"-", "_"} or "0" <= c <= "9" or "a" <= c <= "z" or "A" <= c <= "Z"
+        ):
+            c = "_"
+        # FNV-1: multiply then XOR
+        hash_value = (hash_value * 16777619) & 0xFFFFFFFF
+        hash_value ^= ord(c)
+    return hash_value
+
+
 def strip_accents(value: str) -> str:
     """Remove accents from a string."""
     import unicodedata

tests/integration/fixtures/fnv1_hash_object_id.yaml

@@ -0,0 +1,76 @@
+esphome:
+  name: fnv1-hash-object-id-test
+  platformio_options:
+    build_flags:
+      - "-DDEBUG"
+  on_boot:
+    - lambda: |-
+        using esphome::fnv1_hash_object_id;
+
+        // Test basic lowercase (hash matches Python fnv1_hash_object_id("foo"))
+        uint32_t hash_foo = fnv1_hash_object_id("foo", 3);
+        if (hash_foo == 0x408f5e13) {
+          ESP_LOGI("FNV1_OID", "foo PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "foo FAILED: 0x%08x != 0x408f5e13", hash_foo);
+        }
+
+        // Test uppercase conversion (should match lowercase)
+        uint32_t hash_Foo = fnv1_hash_object_id("Foo", 3);
+        if (hash_Foo == 0x408f5e13) {
+          ESP_LOGI("FNV1_OID", "upper PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "upper FAILED: 0x%08x != 0x408f5e13", hash_Foo);
+        }
+
+        // Test space to underscore conversion ("foo bar" -> "foo_bar")
+        uint32_t hash_space = fnv1_hash_object_id("foo bar", 7);
+        if (hash_space == 0x3ae35aa1) {
+          ESP_LOGI("FNV1_OID", "space PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "space FAILED: 0x%08x != 0x3ae35aa1", hash_space);
+        }
+
+        // Test underscore preserved ("foo_bar")
+        uint32_t hash_underscore = fnv1_hash_object_id("foo_bar", 7);
+        if (hash_underscore == 0x3ae35aa1) {
+          ESP_LOGI("FNV1_OID", "underscore PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "underscore FAILED: 0x%08x != 0x3ae35aa1", hash_underscore);
+        }
+
+        // Test hyphen preserved ("foo-bar")
+        uint32_t hash_hyphen = fnv1_hash_object_id("foo-bar", 7);
+        if (hash_hyphen == 0x438b12e3) {
+          ESP_LOGI("FNV1_OID", "hyphen PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "hyphen FAILED: 0x%08x != 0x438b12e3", hash_hyphen);
+        }
+
+        // Test special chars become underscore ("foo!bar" -> "foo_bar")
+        uint32_t hash_special = fnv1_hash_object_id("foo!bar", 7);
+        if (hash_special == 0x3ae35aa1) {
+          ESP_LOGI("FNV1_OID", "special PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "special FAILED: 0x%08x != 0x3ae35aa1", hash_special);
+        }
+
+        // Test complex name ("My Sensor Name" -> "my_sensor_name")
+        uint32_t hash_complex = fnv1_hash_object_id("My Sensor Name", 14);
+        if (hash_complex == 0x2760962a) {
+          ESP_LOGI("FNV1_OID", "complex PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "complex FAILED: 0x%08x != 0x2760962a", hash_complex);
+        }
+
+        // Test empty string returns FNV1_OFFSET_BASIS
+        uint32_t hash_empty = fnv1_hash_object_id("", 0);
+        if (hash_empty == 0x811c9dc5) {
+          ESP_LOGI("FNV1_OID", "empty PASSED");
+        } else {
+          ESP_LOGE("FNV1_OID", "empty FAILED: 0x%08x != 0x811c9dc5", hash_empty);
+        }
+
+host:
+api:
+logger:

tests/integration/test_fnv1_hash_object_id.py

@@ -0,0 +1,75 @@
+"""Integration test for fnv1_hash_object_id function.
+
+This test verifies that the C++ fnv1_hash_object_id() function in
+esphome/core/helpers.h produces the same hash values as the Python
+fnv1_hash_object_id() function in esphome/helpers.py.
+
+If this test fails, one of the implementations has diverged and needs
+to be updated to match the other.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import re
+
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_fnv1_hash_object_id(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Test that C++ fnv1_hash_object_id matches Python implementation."""
+
+    test_results: dict[str, str] = {}
+    all_tests_complete = asyncio.Event()
+    expected_tests = {
+        "foo",
+        "upper",
+        "space",
+        "underscore",
+        "hyphen",
+        "special",
+        "complex",
+        "empty",
+    }
+
+    def on_log_line(line: str) -> None:
+        """Capture log lines with test results."""
+        # Strip ANSI escape codes
+        clean_line = re.sub(r"\x1b\[[0-9;]*m", "", line)
+        # Look for our test result messages
+        # Format: "[timestamp][level][FNV1_OID:line]: test_name PASSED"
+        match = re.search(r"\[FNV1_OID:\d+\]:\s+(\w+)\s+(PASSED|FAILED)", clean_line)
+        if match:
+            test_name = match.group(1)
+            result = match.group(2)
+            test_results[test_name] = result
+            if set(test_results.keys()) >= expected_tests:
+                all_tests_complete.set()
+
+    async with (
+        run_compiled(yaml_config, line_callback=on_log_line),
+        api_client_connected() as client,
+    ):
+        device_info = await client.device_info()
+        assert device_info is not None
+        assert device_info.name == "fnv1-hash-object-id-test"
+
+        # Wait for all tests to complete or timeout
+        try:
+            await asyncio.wait_for(all_tests_complete.wait(), timeout=2.0)
+        except TimeoutError:
+            pytest.fail(f"Tests timed out. Got results for: {set(test_results.keys())}")
+
+        # Verify all tests passed
+        for test_name in expected_tests:
+            assert test_name in test_results, f"{test_name} test not found"
+            assert test_results[test_name] == "PASSED", (
+                f"{test_name} test failed - C++ and Python hash mismatch"
+            )

tests/unit_tests/test_helpers.py

@@ -279,6 +279,77 @@ def test_sanitize(text, expected):
     assert actual == expected
 
 
+@pytest.mark.parametrize(
+    ("name", "expected_hash"),
+    (
+        # Basic strings - hash of snake_case(sanitize(name))
+        ("foo", 0x408F5E13),
+        ("Foo", 0x408F5E13),  # Same as "foo" (lowercase)
+        ("FOO", 0x408F5E13),  # Same as "foo" (lowercase)
+        # Spaces become underscores
+        ("foo bar", 0x3AE35AA1),  # Transforms to "foo_bar"
+        ("Foo Bar", 0x3AE35AA1),  # Same (lowercase + underscore)
+        # Already snake_case
+        ("foo_bar", 0x3AE35AA1),
+        # Special chars become underscores
+        ("foo!bar", 0x3AE35AA1),  # Transforms to "foo_bar"
+        ("foo@bar", 0x3AE35AA1),  # Transforms to "foo_bar"
+        # Hyphens are preserved
+        ("foo-bar", 0x438B12E3),
+        # Numbers are preserved
+        ("foo123", 0xF3B0067D),
+        # Empty string
+        ("", 0x811C9DC5),  # FNV1_OFFSET_BASIS (no chars processed)
+        # Single char
+        ("a", 0x050C5D7E),
+        # Mixed case and spaces
+        ("My Sensor Name", 0x2760962A),  # Transforms to "my_sensor_name"
+    ),
+)
+def test_fnv1_hash_object_id(name, expected_hash):
+    """Test fnv1_hash_object_id produces expected hashes.
+
+    These expected values were computed to match the C++ implementation
+    in esphome/core/helpers.h. If this test fails after modifying either
+    implementation, ensure both Python and C++ versions stay in sync.
+    """
+    actual = helpers.fnv1_hash_object_id(name)
+
+    assert actual == expected_hash
+
+
+def _fnv1_hash_py(s: str) -> int:
+    """Python implementation of FNV-1 hash for verification."""
+    hash_val = 2166136261  # FNV1_OFFSET_BASIS
+    for c in s:
+        hash_val = (hash_val * 16777619) & 0xFFFFFFFF  # FNV1_PRIME
+        hash_val ^= ord(c)
+    return hash_val
+
+
+@pytest.mark.parametrize(
+    "name",
+    (
+        "Simple",
+        "With Space",
+        "MixedCase",
+        "special!@#chars",
+        "already_snake_case",
+        "123numbers",
+    ),
+)
+def test_fnv1_hash_object_id_matches_manual_calculation(name):
+    """Verify fnv1_hash_object_id matches snake_case + sanitize + standard FNV-1."""
+    # Manual calculation: snake_case -> sanitize -> fnv1_hash
+    transformed = helpers.sanitize(helpers.snake_case(name))
+    expected = _fnv1_hash_py(transformed)
+
+    # Direct calculation via fnv1_hash_object_id
+    actual = helpers.fnv1_hash_object_id(name)
+
+    assert actual == expected
+
+
 @pytest.mark.parametrize(
     "text, expected",
     ((["127.0.0.1", "fe80::1", "2001::2"], ["2001::2", "127.0.0.1", "fe80::1"]),),