From 18c97a08c38193e4a2807c254a4ff52f265f2f28 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Tue, 25 Nov 2025 01:47:06 -0600
Subject: [PATCH] [esp8266] Use C++17 nested namespaces and constexpr (#12096)

---
 esphome/components/esp8266/core.h          |  4 +---
 esphome/components/esp8266/gpio.cpp        |  9 +++++----
 esphome/components/esp8266/gpio.h          |  6 ++----
 esphome/components/esp8266/preferences.cpp | 20 ++++++++++----------
 esphome/components/esp8266/preferences.h   |  6 ++----
 5 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/esphome/components/esp8266/core.h b/esphome/components/esp8266/core.h
index ac3330566..1abe67be8 100644
--- a/esphome/components/esp8266/core.h
+++ b/esphome/components/esp8266/core.h
@@ -7,8 +7,6 @@
 extern const uint8_t ESPHOME_ESP8266_GPIO_INITIAL_MODE[16];
 extern const uint8_t ESPHOME_ESP8266_GPIO_INITIAL_LEVEL[16];
 
-namespace esphome {
-namespace esp8266 {}  // namespace esp8266
-}  // namespace esphome
+namespace esphome::esp8266 {}  // namespace esphome::esp8266
 
 #endif  // USE_ESP8266
diff --git a/esphome/components/esp8266/gpio.cpp b/esphome/components/esp8266/gpio.cpp
index ee3683c67..17a495bc1 100644
--- a/esphome/components/esp8266/gpio.cpp
+++ b/esphome/components/esp8266/gpio.cpp
@@ -3,8 +3,7 @@
 #include "gpio.h"
 #include "esphome/core/log.h"
 
-namespace esphome {
-namespace esp8266 {
+namespace esphome::esp8266 {
 
 static const char *const TAG = "esp8266";
 
@@ -110,9 +109,11 @@ void ESP8266GPIOPin::digital_write(bool value) {
 }
 void ESP8266GPIOPin::detach_interrupt() const { detachInterrupt(pin_); }
 
-}  // namespace esp8266
+}  // namespace esphome::esp8266
 
-using namespace esp8266;
+namespace esphome {
+
+using esp8266::ISRPinArg;
 
 bool IRAM_ATTR ISRInternalGPIOPin::digital_read() {
   auto *arg = reinterpret_cast<ISRPinArg *>(this->arg_);
diff --git a/esphome/components/esp8266/gpio.h b/esphome/components/esp8266/gpio.h
index a1b6d79b3..213a5c54b 100644
--- a/esphome/components/esp8266/gpio.h
+++ b/esphome/components/esp8266/gpio.h
@@ -5,8 +5,7 @@
 #include "esphome/core/hal.h"
 #include <Arduino.h>
 
-namespace esphome {
-namespace esp8266 {
+namespace esphome::esp8266 {
 
 class ESP8266GPIOPin : public InternalGPIOPin {
  public:
@@ -33,7 +32,6 @@ class ESP8266GPIOPin : public InternalGPIOPin {
   gpio::Flags flags_{};
 };
 
-}  // namespace esp8266
-}  // namespace esphome
+}  // namespace esphome::esp8266
 
 #endif  // USE_ESP8266
diff --git a/esphome/components/esp8266/preferences.cpp b/esphome/components/esp8266/preferences.cpp
index a26e9cc49..197d244dc 100644
--- a/esphome/components/esp8266/preferences.cpp
+++ b/esphome/components/esp8266/preferences.cpp
@@ -15,24 +15,24 @@ extern "C" {
 #include <cstring>
 #include <memory>
 
-namespace esphome {
-namespace esp8266 {
+namespace esphome::esp8266 {
 
 static const char *const TAG = "esp8266.preferences";
 
-static bool s_prevent_write = false;         // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 static uint32_t *s_flash_storage = nullptr;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+static bool s_prevent_write = false;         // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 static bool s_flash_dirty = false;           // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
-static const uint32_t ESP_RTC_USER_MEM_START = 0x60001200;
+static constexpr uint32_t ESP_RTC_USER_MEM_START = 0x60001200;
+static constexpr uint32_t ESP_RTC_USER_MEM_SIZE_WORDS = 128;
+static constexpr uint32_t ESP_RTC_USER_MEM_SIZE_BYTES = ESP_RTC_USER_MEM_SIZE_WORDS * 4;
+
 #define ESP_RTC_USER_MEM ((uint32_t *) ESP_RTC_USER_MEM_START)
-static const uint32_t ESP_RTC_USER_MEM_SIZE_WORDS = 128;
-static const uint32_t ESP_RTC_USER_MEM_SIZE_BYTES = ESP_RTC_USER_MEM_SIZE_WORDS * 4;
 
 #ifdef USE_ESP8266_PREFERENCES_FLASH
-static const uint32_t ESP8266_FLASH_STORAGE_SIZE = 128;
+static constexpr uint32_t ESP8266_FLASH_STORAGE_SIZE = 128;
 #else
-static const uint32_t ESP8266_FLASH_STORAGE_SIZE = 64;
+static constexpr uint32_t ESP8266_FLASH_STORAGE_SIZE = 64;
 #endif
 
 static inline bool esp_rtc_user_mem_read(uint32_t index, uint32_t *dest) {
@@ -284,10 +284,10 @@ void setup_preferences() {
 }
 void preferences_prevent_write(bool prevent) { s_prevent_write = prevent; }
 
-}  // namespace esp8266
+}  // namespace esphome::esp8266
 
+namespace esphome {
 ESPPreferences *global_preferences;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
-
 }  // namespace esphome
 
 #endif  // USE_ESP8266
diff --git a/esphome/components/esp8266/preferences.h b/esphome/components/esp8266/preferences.h
index edec91579..16cf80a12 100644
--- a/esphome/components/esp8266/preferences.h
+++ b/esphome/components/esp8266/preferences.h
@@ -2,13 +2,11 @@
 
 #ifdef USE_ESP8266
 
-namespace esphome {
-namespace esp8266 {
+namespace esphome::esp8266 {
 
 void setup_preferences();
 void preferences_prevent_write(bool prevent);
 
-}  // namespace esp8266
-}  // namespace esphome
+}  // namespace esphome::esp8266
 
 #endif  // USE_ESP8266