From a92281f899e57b80f9aee5e4bea473c051940a0e Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sun, 22 Mar 2026 21:24:01 -1000
Subject: [PATCH] Add tests for register_component_source, remove redundant
 index check

- Test empty name returns 0
- Test deduplication returns same index
- Test overflow warns and returns 0
- Remove duplicate index==0 check in get_component_log_str() since
  component_source_lookup() already handles it
---
 esphome/core/component.cpp           |  3 +--
 tests/unit_tests/test_cpp_helpers.py | 31 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/esphome/core/component.cpp b/esphome/core/component.cpp
index 44194a18a85..c81e357808c 100644
--- a/esphome/core/component.cpp
+++ b/esphome/core/component.cpp
@@ -275,8 +275,7 @@ void Component::call() {
   }
 }
 const LogString *Component::get_component_log_str() const {
-  return this->component_source_index_ == 0 ? LOG_STR("<unknown>")
-                                            : component_source_lookup(this->component_source_index_);
+  return component_source_lookup(this->component_source_index_);
 }
 bool Component::should_warn_of_blocking(uint32_t blocking_time) {
   // Convert centisecond threshold to milliseconds for comparison
diff --git a/tests/unit_tests/test_cpp_helpers.py b/tests/unit_tests/test_cpp_helpers.py
index b2b0d14a3d0..75b96bb9e07 100644
--- a/tests/unit_tests/test_cpp_helpers.py
+++ b/tests/unit_tests/test_cpp_helpers.py
@@ -1,8 +1,10 @@
+import logging
 from unittest.mock import Mock
 
 import pytest
 
 from esphome import const, cpp_helpers as ch
+from esphome.cpp_helpers import ComponentSourcePool, register_component_source
 
 
 @pytest.mark.asyncio
@@ -78,3 +80,32 @@ async def test_register_component__with_setup_priority(monkeypatch):
     assert add_mock.call_count == 4
     app_mock.register_component_.assert_called_with(var)
     assert core_mock.component_ids == []
+
+
+def test_register_component_source_empty_name(monkeypatch):
+    monkeypatch.setattr(ch, "CORE", Mock(data={}))
+    assert register_component_source("") == 0
+
+
+def test_register_component_source_deduplicates(monkeypatch):
+    monkeypatch.setattr(ch, "CORE", Mock(data={}))
+    idx1 = register_component_source("wifi")
+    idx2 = register_component_source("api")
+    idx3 = register_component_source("wifi")
+    assert idx1 == 1
+    assert idx2 == 2
+    assert idx3 == 1  # deduplicated
+
+
+def test_register_component_source_overflow_warns(monkeypatch, caplog):
+    # Pre-fill pool to max
+    pool = ComponentSourcePool(
+        sources={f"comp_{i}": i + 1 for i in range(0xFF)},
+        table_registered=True,
+    )
+    monkeypatch.setattr(ch, "CORE", Mock(data={ch._COMPONENT_SOURCE_DOMAIN: pool}))
+    with caplog.at_level(logging.WARNING):
+        idx = register_component_source("overflow_component")
+    assert idx == 0
+    assert "Too many unique component source names" in caplog.text
+    assert "overflow_component" in caplog.text