From f8bda9fbad897d10aadf847ea2fd03fea20cb125 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sun, 13 Sep 2026 23:53:41 -0500
Subject: [PATCH] [logger] Skip the hardware UART setter when it matches the
 default (#19230)

---
 esphome/components/logger/__init__.py         | 13 ++++----
 esphome/components/logger/logger.h            |  4 +--
 tests/component_tests/logger/test_logger.py   | 32 +++++++++++++++++++
 .../logger/test_logger_libretiny_default.yaml |  8 +++++
 .../logger/test_logger_libretiny_uart0.yaml   |  9 ++++++
 .../logger/test_logger_uart1.yaml             |  9 ++++++
 6 files changed, 67 insertions(+), 8 deletions(-)
 create mode 100644 tests/component_tests/logger/test_logger_libretiny_default.yaml
 create mode 100644 tests/component_tests/logger/test_logger_libretiny_uart0.yaml
 create mode 100644 tests/component_tests/logger/test_logger_uart1.yaml

diff --git a/esphome/components/logger/__init__.py b/esphome/components/logger/__init__.py
index 07b8b030840..138db75ad10 100644
--- a/esphome/components/logger/__init__.py
+++ b/esphome/components/logger/__init__.py
@@ -362,12 +362,13 @@ async def to_code(config: ConfigType) -> None:
     # pre_setup() switches on uart_ to decide which hardware to initialize
     # (e.g. UART0 vs USB_SERIAL_JTAG). Without this, uart_ is still the
     # default UART_SELECTION_UART0 and the wrong hardware gets initialized.
-    if CONF_HARDWARE_UART in config:
-        cg.add(
-            log.set_uart_selection(
-                HARDWARE_UART_TO_UART_SELECTION[config[CONF_HARDWARE_UART]]
-            )
-        )
+    # uart_ is UART0 in C++ except on LibreTiny where it is DEFAULT; skip the
+    # setter when the config matches it.
+    cpp_default_uart = DEFAULT if CORE.is_libretiny else UART0
+    if (
+        hardware_uart := config.get(CONF_HARDWARE_UART)
+    ) is not None and hardware_uart != cpp_default_uart:
+        cg.add(log.set_uart_selection(HARDWARE_UART_TO_UART_SELECTION[hardware_uart]))
     # pre_setup() sets global_logger and must run before any other code
     # that may call ESP_LOG* (e.g. setup_preferences contains ESP_LOGVV).
     cg.add(log.pre_setup())
diff --git a/esphome/components/logger/logger.h b/esphome/components/logger/logger.h
index 9c26814f7ec..ae55f4145a9 100644
--- a/esphome/components/logger/logger.h
+++ b/esphome/components/logger/logger.h
@@ -352,10 +352,10 @@ class Logger final : public Component {
   // Group smaller types together at the end
   uint8_t current_level_{ESPHOME_LOG_LEVEL_VERY_VERBOSE};
 #if defined(USE_ESP32) || defined(USE_ESP8266) || defined(USE_RP2) || defined(USE_ZEPHYR)
-  UARTSelection uart_{UART_SELECTION_UART0};
+  UARTSelection uart_{UART_SELECTION_UART0};  // Must match cpp_default_uart in __init__.py
 #endif
 #ifdef USE_LIBRETINY
-  UARTSelection uart_{UART_SELECTION_DEFAULT};
+  UARTSelection uart_{UART_SELECTION_DEFAULT};  // Must match cpp_default_uart in __init__.py
 #endif
 #if defined(USE_ESP32) || defined(USE_HOST) || defined(USE_LIBRETINY) || defined(USE_ZEPHYR)
   bool main_task_recursion_guard_{false};
diff --git a/tests/component_tests/logger/test_logger.py b/tests/component_tests/logger/test_logger.py
index 94a6f7ac7bc..4ce30afb946 100644
--- a/tests/component_tests/logger/test_logger.py
+++ b/tests/component_tests/logger/test_logger.py
@@ -52,3 +52,35 @@ def test_logger_pre_setup_before_other_components(generate_main):
             f"Component allocation '{alloc.group()}' at position {alloc.start()} "
             f"appears before logger pre_setup() at position {logger_pre_setup.start()}"
         )
+
+
+def test_default_uart_selection_is_not_emitted(generate_main):
+    """UART0 is the C++ initializer on ESP8266, so the setter is skipped."""
+    main_cpp = generate_main("tests/component_tests/logger/test_logger.yaml")
+
+    assert "set_uart_selection(" not in main_cpp
+
+
+def test_custom_uart_selection_is_emitted(generate_main):
+    """A non default UART still reaches the setter before pre_setup()."""
+    main_cpp = generate_main("tests/component_tests/logger/test_logger_uart1.yaml")
+
+    assert "set_uart_selection(logger::UART_SELECTION_UART1);" in main_cpp
+
+
+def test_libretiny_default_uart_selection_is_not_emitted(generate_main):
+    """DEFAULT is the C++ initializer on LibreTiny, so the setter is skipped."""
+    main_cpp = generate_main(
+        "tests/component_tests/logger/test_logger_libretiny_default.yaml"
+    )
+
+    assert "set_uart_selection(" not in main_cpp
+
+
+def test_libretiny_uart0_is_emitted(generate_main):
+    """UART0 is not the LibreTiny initializer, so it must still be set."""
+    main_cpp = generate_main(
+        "tests/component_tests/logger/test_logger_libretiny_uart0.yaml"
+    )
+
+    assert "set_uart_selection(logger::UART_SELECTION_UART0);" in main_cpp
diff --git a/tests/component_tests/logger/test_logger_libretiny_default.yaml b/tests/component_tests/logger/test_logger_libretiny_default.yaml
new file mode 100644
index 00000000000..1f11ea4580c
--- /dev/null
+++ b/tests/component_tests/logger/test_logger_libretiny_default.yaml
@@ -0,0 +1,8 @@
+---
+esphome:
+  name: test
+
+rtl87xx:
+  board: generic-rtl8710bn-2mb-788k
+
+logger:
diff --git a/tests/component_tests/logger/test_logger_libretiny_uart0.yaml b/tests/component_tests/logger/test_logger_libretiny_uart0.yaml
new file mode 100644
index 00000000000..dc25fe99ce2
--- /dev/null
+++ b/tests/component_tests/logger/test_logger_libretiny_uart0.yaml
@@ -0,0 +1,9 @@
+---
+esphome:
+  name: test
+
+rtl87xx:
+  board: generic-rtl8710bn-2mb-788k
+
+logger:
+  hardware_uart: UART0
diff --git a/tests/component_tests/logger/test_logger_uart1.yaml b/tests/component_tests/logger/test_logger_uart1.yaml
new file mode 100644
index 00000000000..ce45a6ae3fb
--- /dev/null
+++ b/tests/component_tests/logger/test_logger_uart1.yaml
@@ -0,0 +1,9 @@
+---
+esphome:
+  name: test
+
+esp8266:
+  board: d1_mini_lite
+
+logger:
+  hardware_uart: UART1